Thoughts on moisture problem inside insulators/and distributor caps :VIDEO

[JC220]

Re the bottom vent slots - water vapour does not disperse in a downwards direction. Which is why I think the factory setup leaves alot to be desired.

Await my thoughts and experiment in a couple of hours. As I said I have many angles of thought on this (Not just the vents) and a new thread may be more prudent.

 

[gerryvz]

I never had a problem during the 10 years I lived in Texas (though my car was always garaged) -- it was quite humid and my car could go for weeks (and occasionally a month or two) without being driven. Never had a bit of problem.

 

[195910]

Why did this not occur when these cars were newer?

Many of us have owned 124036 for more the a decade and we never had this issue 15-20 years ago even with stored cars.

 

[Russell R Coe]

All, I have had this issue on going for about three years. If I leave the car (1992 model) parked for over over 6 days, it will start fine every time, but within two minutes it will start the misfiring and running very badly like it is only running on six or less cylinders. If I start it after 5 days no problems at all, the the longer I leave it parked, I was away for three week recently, the worse it will be. Starts fine I will get about three minutes into the drive and it gets really bad. This last time after my three week vacation, I got stuck in bad traffic and I really thought it was going to stall on me. After about 20 to 25 minutes crawling along it just cleared up and the car ran beautifully, not a miss or any signs of hesitation.

I had the rotors, caps and insulator seals replaced that helped for about six months, but it is now back to as bad as before they were replaced.

I have considered putting adsorption material around the coils while it is parked, as it does not matter if it is at home in my garage or parked in the covered parking at my work. The results after six days are the same. Not a good idea if your forget that you put it there and fire it up.
I live in the San Francisco Bay area so it does not really get that cold or damp, and the car is always in undercover parking at work, or in the garage at home.

I look forward to any experiments that may work to fix the madding issue.

The mystery continues.

 

[gsxr]

I had the rotors, caps and insulator seals replaced that helped for about six months, but it is now back to as bad as before they were replaced.

Russell, have you had the insulators replaced with new, or only the seal/O-ring?

 

[Russell R Coe]

Dave, the insulators were new, not the seals

 

[Efraim]

Why did this not occur when these cars were newer?

They say that original distrbutor caps (MB part) were lacquer coated, while Bosch ones doesn't. This may cause the difference.

 

[gsxr]

Dave, the insulators were new, not the seals

Hmmm. Next time the car is parked over a week, I'd pull both caps + insulators and inspect for any signs of liquid, anywhere... and also any signs of carbon tracks from misfiring. I had a nearly identical issue as yours, but new insulators cured it permanently. Just curious, what brand caps/rotors did you buy? (The insulators are only available from Bosch now.)

They say that original distrbutor caps (MB part) were lacquer coated, while Bosch ones doesn't. This may cause the difference.

True... but rumor is, the OE MB caps are no longer lacquer coated. Think there was a thread discussing this a year or two ago? I'm not sure how much difference the coating makes.

 

[JC220]

I never had a problem during the 10 years I lived in Texas (though my car was always garaged) -- it was quite humid and my car could go for weeks (and occasionally a month or two) without being driven. Never had a bit of problem.

Gerry, your experience will vary! Indeed every member’s experience can and WILL vary since we are all over the world. Some other factors:

• Humidity levels and ambient temperatures in your area
• How frequent the car is fully warmed up driven
• How the car is stored – outside – inside - and the temperature / ventilation conditions of said storage
• Condition of the Ignition system
• Condition of camshaft oil seal rings
  • 
    My 500E has never suffered this water vapour in caps before in just over 3 years of ownership. I believe this is because it was always stored inside in my dry, heated, double glazed and fully insulated garage attached to my home. (Optimum conditions VS outside in a carport with 2no open ends like recent months)
    
    I believe that this problem is only now occurring because my storage conditions through winter have changed and the car sat dis-used for longer periods. Therefore my 500E was suddenly within the scope of the set of parameters that this issue can occur within.
    
    To say that because one members car never had this fault, is not to say that it could not be an issue with other people’s cars. IMHO – and respectfully.
    
    

    Why did this not occur when these cars were newer?
    
    Many of us have owned 124036 for more the a decade and we never had this issue 15-20 years ago even with stored cars.

    
    Very likely the same reasons stated above. IE; when these cars were new they would have been driven alot more frequently throughout the year whereas now among the other factors (EG: aging ignition system) we have 500Es that are generally, for most members - second or third cars. Cosseted classics in other words, that see long periods of dis-use like winter storage compounding the problem where (un)favourable conditions exist for the problem to occur.
    
    

    I keep reading about the insulator O-ring as being a problem, and that replacing it will somehow fix things. I don't think anyone understands how little that O-ring does. AFAICT, it primarily is a dust seal, and provides a soft barrier between the cap and insulator. There was a lot of speculation, SWAG's, and not much useful info in that thread. Drilling a hole in the oil fill cap to relieve excess crankcase pressure was an awesome suggestion. (Not!)
    
    I'm not convinced the bottome vent slots are a problem to be "fixed". We've already proven that the mystery liquid which collects on the back of insulators is not water - if the damp insulator is removed and left to sit out for days, the liquid never evaporates. I'm also not entirely convinced the liquid is condensed oil vapor being pushed out the seal, but that is a possibility.
    
    If it is water condensation inside the caps, I'm not sure what the solution is. But again, as mentioned above, this only seems to happen when a car is parked in a humid environment for months. Why doesn't every M119 in a tropical environment have major problems? I mean, you'd think every one in Florida or Hawai'i would spend most of the time in the shop if not driven daily.
    
    I don't know the solution, and I'm still not sure of the root cause, but the more experiments are performed & recorded the more it will help narrow down the root cause.
    
    

    
    
    I agree Dave – the O rings here do little to nothing at all. Merely a dust guard of sorts.
    
    
    

    All, I have had this issue on going for about three years. If I leave the car (1992 model) parked for over over 6 days, it will start fine every time, but within two minutes it will start the misfiring and running very badly like it is only running on six or less cylinders. If I start it after 5 days no problems at all, the the longer I leave it parked, I was away for three week recently, the worse it will be. Starts fine I will get about three minutes into the drive and it gets really bad. This last time after my three week vacation, I got stuck in bad traffic and I really thought it was going to stall on me. After about 20 to 25 minutes crawling along it just cleared up and the car ran beautifully, not a miss or any signs of hesitation.
    
    I had the rotors, caps and insulator seals replaced that helped for about six months, but it is now back to as bad as before they were replaced.
    
    I have considered putting adsorption material around the coils while it is parked, as it does not matter if it is at home in my garage or parked in the covered parking at my work. The results after six days are the same. Not a good idea if your forget that you put it there and fire it up.
    I live in the San Francisco Bay area so it does not really get that cold or damp, and the car is always in undercover parking at work, or in the garage at home.
    
    I look forward to any experiments that may work to fix the madding issue.
    
    The mystery continues.

    Dave, the insulators were new, not the seals

    
    
    Removing and renewing ignition components will of course give temporary reprieve from this moisture buildup problem. Because you are drying out the area and fitting new clean parts before the slow cycle starts all over again in the coming weeks – months. Your description aligns exactly with my thoughts on this subject.
    
    
    My experiment was carried out and see the photos below. I had 4x clear paint pots with equal amount of fluid in a shot glass in all 4x.
    
    
    • 1st was control (Uncut)
    • 2nd had a bottom cut only – like M119 caps essentially
    • 3rd had top only cut
    • 4th had both bottom and top cuts.
    
    Notice when looking at the following pictures what happens:
    
    Control is reaching saturation levels- as expected:
    
    
    
    Bottom cut only- pretty close to the control. Little to no effect of bottom only venting. This is why I say that I see a design flaw there in the MB cap design for the m119. Bottom vent only is ineffective for condensation drainage in a sealed void:
    
    
    
    Top cut only – visual improvement VS previous 2x:
    
    
    
    
    Bottom and Top cuts- the least amount of condensation – makes quite a difference inside! Best condition of the lot.
    
    
    
    As an Architectural Technician by trade I have a good understanding of how to properly ventilate a given space and the m119 distributor cap is no different to those principles. The experiment was for my benefit to see for myself how moisture can condense and get trapped inside my 500E’s cap.
    
    I also have a 300E-24 with distributer cap parked for the identical period of time and conditions as my 500E...... yet it is not stalling, dying out. What gives?
    
    Let’s look and see: (Pics from my own cars)
    
    M119 Cap vents – 2x primary locations at the bottom of the cap when fitted:
    
    
    
    M104 Cap Vents- many more vents situated all around the cap and more importantly IMO – BOTH top and bottom.
    
    
    
    IMO this is why my 300E-24 can cope OK but my 500E is impacted by moisture. Therefore I have satisfied myself if nothing else that I should cut more ventilation slots in my 500E's caps, in particular through the top in both caps with a dremel in order to allow moisture trapped in there to escape as the motor warms up.
    
    I will take photos of the slots cutting in a day or two

 

[gsxr]

Interesting that the M104 cap has more slots around the circumference - I did not know that!

Arnt posted a few years ago about adding vent slots at the top of the M119 caps, I think he said it did help, but I can't remember details offhand.

 

[Russell R Coe]

JC220

I look forward to seeing the results of you experiment.

I drive my car weekly so that I don't have to deal with the issue, except when I cannot.

 

[Jlaa]

I'm not convinced the bottome vent slots are a problem to be "fixed". We've already proven that the mystery liquid which collects on the back of insulators is not water - if the damp insulator is removed and left to sit out for days, the liquid never evaporates. ...

If it is water condensation inside the caps, I'm not sure what the solution is. But again, as mentioned above, this only seems to happen when a car is parked in a humid environment for months. Why doesn't every M119 in a tropical environment have major problems? I mean, you'd think every one in Florida or Hawai'i would spend most of the time in the shop if not driven daily.

Maybe we see the effect of JC220's "top re-oriented vent slots in the distributor cap" experiment to bring us one step closer? If JC220's experiment yields no progress, then perhaps we go back to the observation that the liquid is not water.

If the liquid is not water then it is --- crankcase fumes? And if it is crankcase fumes, then maybe some combination of ambient temp/humidity causes dissimilar contraction/expansion rates of aluminum / bakelite / rubber seals to allow the crankcase fumes (with vapor) into the distributor cap?

 

[sheward]

One of my 036s sits for extended periods of time between runnings and does not experience the problem, and the insulators have not been changed in many years. More than 10. It does have newer caps that were purchased before folks started to experience the problem. Makes me wonder if this "liquid" is leaching out of the newer caps or insulators.

drew

 

[JC220]

I'm not convinced the bottome vent slots are a problem to be "fixed". We've already proven that the mystery liquid which collects on the back of insulators is not water - if the damp insulator is removed and left to sit out for days, the liquid never evaporates. I'm also not entirely convinced the liquid is condensed oil vapor being pushed out the seal, but that is a possibility.

If it is water condensation inside the caps, I'm not sure what the solution is. But again, as mentioned above, this only seems to happen when a car is parked in a humid environment for months. Why doesn't every M119 in a tropical environment have major problems? I mean, you'd think every one in Florida or Hawai'i would spend most of the time in the shop if not driven daily.

I don't know the solution, and I'm still not sure of the root cause, but the more experiments are performed & recorded the more it will help narrow down the root cause.

One of my 036s sits for extended periods of time between runnings and does not experience the problem, and the insulators have not been changed in many years. More than 10. It does have newer caps that were purchased before folks started to experience the problem. Makes me wonder if this "liquid" is leaching out of the newer caps or insulators.

drew

Re the mystery clear sticky residue buildup.

The cam oil seal being behind the insulating cup is a good explanation for a source of this contamination. I believe this is a substance that builds up over a long period of time as a by product of crankcase vapours. (Oil droplets, fuel, moisture contamination in oil etc due to cold start-up blowby gases) Perhaps these small amounts of crankcase vapours getting past the oil seal ring(s) are condensing and mixing with “normal” moisture which boils off the cap and leaves this sticky residue behind.

It’s got to be that IMO. Is it resins leaching out of aging plastics? Good idea also but I doubt that myself. What I do know is this sticky fluid is not unique to the m119. It was on my m104 Cap also – same scenario with cam oil seal. (I wiped this sticky residue off with WD40 when I first took the m104 cap off yesterday) That cap is about 4 years old Bosch, not covered many miles either maybe 200 ish but lots of cold starts moving the car around during those years.

It does take a long time for this sticky stuff to buildup – this is where periodic cleaning of both the distributer cap and all sides of the insulating cup is required IMO. Once every 12 to 18 months wouldn’t be too difficult to do that task and that is my new plan for both my 500E and 300E-24 to keep this oil contamination at bay.

You can 100% cure this issue with a new insulating cup and / or a distributer cap. But then again wouldn’t cleaning give the same immediate results (VS new caps) in terms of excess sticky residue?

My 500E insulating cups were cleaned very few miles ago and everything else was new – I had no sticky residue. My 500E breakdown this week – was not this sticky buildup! It was plain old water condensation easily wiped off with my pinky. Not sticky clear gel type stuff we are talking about here believe me – plain water caused that breakdown.

We are mixing 2x separate issues here.

1: General upkeep is required in distributer systems to keep them healthy, yes this means periodically taking the caps off and cups out to clean them every year or two. The more regular you can do this the better, keeping the sticky build-up at bay.

2: Atmospheric moisture building up inside the caps in unfavourable conditions and not being able to escape as the motor warms up and it moves to the now coldest surface – the furtherest surface inside away from the warming engine – inside of distributer cap at the contacts.

 

[JC220]

I keep reading about the insulator O-ring as being a problem, and that replacing it will somehow fix things. I don't think anyone understands how little that O-ring does. AFAICT, it primarily is a dust seal, and provides a soft barrier between the cap and insulator. There was a lot of speculation, SWAG's, and not much useful info in that thread. Drilling a hole in the oil fill cap to relieve excess crankcase pressure was an awesome suggestion. (Not!)

BTW I wasn’t referring to all theories in that thread – maybe I should have quoted what I found useful instead:

It did, but only on a temporary basis. I use this SL500 for about ten days every three months or so.
I thought I would be clever and take off and inspect the caps before using the car during our last UK trip about two weeks ago.
They appeared bone dry, but to be sure, I wiped them with a dry paper kitchen towel.
We drove two miles to a supermarket for shopping. Returning to the car it wouldn't start. I took off the dist caps, and they were full of moisture!!!!!
Where the hell does it come from?

..................

Update:

In England now, and the same problem. The car started after two weeks away, I drove for around two miles and parked for half an hour. On returning it would not start, so I removed and dried the dist. caps which were moisturised

Back at the house, I stripped one of the distributors for examination.
The oil seal OK with no trace of oil leaking.
The large 70mm. orange O ring was intact with no cracks or splits, albeit a little tired looking. Next time we are over to England, I'll bring two new O rings to try.

At the bottom of each distributor cap are a series of what appear like saw cuts, presumably this is to let any moisture out??? Conversely, maybe this is where moist air is getting in???

....................

I cleaned & wiped dry and replace (reuse) the O ring, ever since then the problem has not come back.

On mine moisture will go away as engine gets warmed up. If I drive the car on daily basis, this does not happen. It happens only when if I let the car sits > 3 days.

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Hi i have a 1991 h 500 SL with this problem at the moment,i bought 2 new bosch distributor caps from main dealer and 2 new o rings,the problem is still apparent but not as bad.Behind the distributor caps there is another plastic shield shaped like a cerial bowl with a hole through the middel for the rotor arm shaft to pass this doesnt appear to have any gaskets at all and seams to just rely on a good fit against the end of the cam housing,i am going to go into the dealers and get them to pull the diagram up for this and see if there should be a gasket i bet the moisture is finding its way past this from behind.

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My UK SL500 is not as far north as Yorkshire, but the moisture just keeps coming back.

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Looking up about M119 engines, it is a common problem depending on where the car is situated.

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I have just been into MB about the possible seal for the bowl shaped thingy with a hole through the middel that sits behind the rotor arm (technical term lol) there is a picture on perma link 4 of this,MB says there never was a seal there so once i got back home this is what i have done:
1. Remove both distributor caps
2. Remove both rotor arms
3. Remove machined aluminium mounts for rotor arms
4. Remove the bowl shaped cover as on perma link 4. Upon removal of this as i thought full of condensation behind it which can only becoming from down the side of the distributor cap and then in between the bowl shaped cover and cam shaft housing end,up the middle hole and in to the distributor.
Cure(fingers crossed):
1. Thouroughly clean all the removed components and end of cam shaft housing of muck and condensation.
2. Run a bead of high temperature gasket sealant around the bottom lip of the bowl circumference and replace.
3. replace rotor arm mounting and rotor arm.

4. Remove O ring from bowl shaped cover and replace with new BUT, before mounting the new O rings you will see 2 machined groves in the bowl where the O ring sits i can only assume these are for putting a flat object to un lip the O rings to aid in removal, place a bead of the sealant in these groves and mount the new O rings.
5. There are some drain groves in the distributor caps fill these also with the gasket sealant and lastly refit.



Finally solved the moisture in my distributor caps,upon doing the alterations i mentioned in a previous thread i have used the car now for a further 250miles in wet and dry weather,i removed the cap to check and no moisture!!!

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I installed new similar sized o-rings and employed "lee2222car"'s fix with the silastic. The moisture has not come back in the last 300 kms so can fully recommend giving it a try.

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SO, as suggested it turned out to be my condensation. Tested the car today. Checked the caps before starting the car, they were dry. Ran it for about 5 mins, let it sit 20 mins then tried a start. It did start but rough. So off with the caps and sure enough fine condensation. Hit them with CRC and bang! smooth start and running. So despite the low mileage (the car has done under 40k miles) the interior cap finish does deteriorate.

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Yes, thats it. Once the caps heat up with the heads then the condensation disapears. SHort runs (i.e. 5 mins) then an engine switch off for say 10 mins also causes condensation. That was the problem with mine. A short run, come back to the car and it was a no go or badly misfiring

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There are factory drilled holes in these distributor caps but they are drilled underneath each cap as they sit in position (perhaps to let moisture out!!)

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I have been testing a similar potential fix for around 4 months now, with promising results.

It occurred to me while watching the TV program 'Wheeler Dealers' about 6 months back where they were talking about the two vents in the fog lights of a Range Rover. The upper vent allows water vapour to escape (which is lighter than air), preventing misting up inside the lenses. The lower vent allows flow of air in.

With regard to 'how this happens', I guess that I could add that the moisture vapour gradually builds up over time until there is sufficient concentration inside the cap for a dew point to form as a result of the vapour pressure and temperature differential. I outlined the cycle on a psychometric chart before I cut the holes in my caps just to be sure.

Instead of drilling a hole I cut more slots in the base of the caps.

The original slots are aligned at approx 4.30 and 7.30 on the clock. This is to let ozone escape, which is heavier than 'air'.

I cut additional slots at approx 2 and 10 o'clock to allow the vapour to escape. So far so good. But proof of the pudding will be how it copes through the winter.

....................

Thanks for the helpful info. Interesting that you don't have this problem in desert environ. This suggests that the theory muted in earlier posts concerning humid blowby gases leaking past the cam seals may not be the primary cause, otherwise you would be experiencing problems too. Although its fair to say it could be a contributory factor if the seals are worn out I guess.

I have been looking into this misfire issue for several months (if not years!). Certainly looks like ambient humidity is the main ingredient. Coupled with differential temperatures caused by thermal conduction through dissimilar materials (alloy - very conductive, phenolic resins etc - insulating), thermal convection, vapour drive from hot to cool (direction subject to cooling or heating cycle), partial vapour pressure, and also that some of the resins I believe are hygroscopic. I plotted the cycle on a Mollier diagram and it all points to a dew point on the inside face of the distributor cap. This dew point can occur even with a hot engine, so long as there is sufficient temperature differential and partial vapour pressure. The temp differential only needs to be around 6 to 9 degC for all the other magic ingredients to come together to create the moisture.

It appears that the Designer was Little Bear in this instance, and he managed to create a Goldilocks distributor where 'Everything was just right'... to produce moisture inside the cap!

With hygroscopic resins, like silica gel desiccant, the moisture is adsorbed, not absorbed, and both these materials release their moisture when heated. The point I am getting to is that silica gel would release its moisture when the engine gets warm, which would lead to the same running issues after a short journey, park up and restart. I don't think silica gel is the answer unfortunately.

For the benefit of all reading this: -

Vent the caps.

I would also suggest trying out Beru caps, because I think that their design is more compatible to solving the problem due to fact that they have an added layer of protection - a smooth imide polymer varnish layer inside the cap.

There are alot of theories floating around that thread linked – not all that we will agree with of course like the drill oil cap GSXR mentioned. Beru caps are also mentioned to maybe be more resistant to moisture than Bosch.

Most of them do all describe a typical moisture related issue occurring not long after cold startup. And methods of sealing the back cap or more importantly that additional cap ventilation appeared to be solving their problem.

My experiment has demonstrated that you cannot adequately allow mositure to evaporate with only lower vent holes. Top and ideally top & bottom vents are required to allow codensation to escape.

Note that many of these people were from the UK – suggesting environment is a primary factor in moisture problems with M119 caps

 

[JC220]

I set my experiment paint cups into the trunk of my S320 and looked at them again this morning:

Control – unvented cup:


Bottom vent slot only – like M119 caps:



Top vent slot only – improvement: (Moisture rises!) But cup sides not clear either



Top and bottom vent slots – clear cup on sides with moisture being able to escape: (Moisture rising and thus creating greater convection - air movement with benefit of a bottom slot)




Tomorrow - Cap drilling or vent slot cutting not sure which will ventilate better but I will decide what mod to do to my 500E's caps

 

[Jlaa]

JC220 ---- what a clever idea to run the experiment with the cups!!!

 

[Russell R Coe]

JC220, very clever indeed.

I'm going away for 6 days in a couple of weeks.

I will pull the caps prior to leaving, and take some photo's. I will Reinstall them untouched. When I return on the 7 day pull them off again and see if there is any difference.
I will report my findings.

 

[tomer]

FWIW, I have recently drove my car just 10 minutes to a wand wash (drove with no issues) and after the wand wash - MISIFRE!!! It took 5-10 minutes to "drive through" the problem and return to normal operation. I did not raise the hood while washing, and only sprayed the grill a little...

 

[ricsim]

I never had a problem during the 10 years I lived in Texas (though my car was always garaged) -- it was quite humid and my car could go for weeks (and occasionally a month or two) without being driven. Never had a bit of problem.

As i write in my post #40
"the bakelite with which the ignition caps is made is supposed to be a good thermal insulator.
I think this bakelite may no longer be of the same quality as the old caps, produced in the 90's)"

In my mind, asbestos was inside the old bakelite.
since many years, asbestos is forbiden and something else is usedinside the new bakelite.

My test is OK for the moment (post #40)
JC220 - I think other holes in the caps could be a good idea.

 

[JC220]

I have gave it a couple of days and drove my 500E tonight. It was perfect no misfiring of any kind so the moisture had built up during the winter months and isn't such an issue just now.

None the less I will be adding more vent slots to both caps this week and will post photos when I do. In reality my 500E will be back in its heated garage before winter so I dont know if I will be able to offer useful data after that point. My 220CE needs welding finished and out of the garage that belongs to the 500E this summer!

 

[tuttebenne]

My 400e would have the problem if we let the car sit for five days no matter Winter or Summer. The car is outside 100% of the time. New caps cured it for a few years but it still does it now and again so I am going for new insulators for it and for the 500e. The 500e just experienced the problem for the first time after a cold start following five months in storage. I don't see any mention of these cars having the problem when they were new so (at least from my own experience) I don't see the need to re-engineer something that seems to work when everything is in top shape.

 

[msq]

any suggestions on good source for best/highest quality distributor caps and insulators?

 

[gsxr]

any suggestions on good source for best/highest quality distributor caps and insulators?

Besides the OE/dealer parts ($$$$):

Caps are available from Bosch (OEM), Beru, and Bremi. I personally like Beru.
Rotors are available from Bosch, Beru (reboxed OEM Doduco), and Bremi. I highly recommend the OE/Beru/Doduco.
Insulators are only available from Bosch (OEM, orange color). The Doduco (black color) are NLA / out of pruoduction.

Photos here: http://www.w124performance.com/images/M119/EZL/caps+rotors/

Bremi is not OEM for these items, but as discussed in older threads, a number of forum members have had good success with Bremi.

 

[2phast]

I have had nothing but problems with the generic Bosch caps/rotors. Went to OE Mercedes caps/rotors, which were also made by Bosch, but they looked quite different from the generic Bosch's. Never had any issues with the OE Bosch till I decided to clean them with a brass brush. Ended up with Beru caps/rotors, which have been great so far. Replaced my insulators with new orange Bosch insulators.

 

[JC220]

I have had nothing but problems with the generic Bosch caps/rotors. Went to OE Mercedes caps/rotors, which were also made by Bosch, but they looked quite different from the generic Bosch's. Never had any issues with the OE Bosch till I decided to clean them with a brass brush. Ended up with Beru caps/rotors, which have been great so far. Replaced my insulators with new orange Bosch insulators.

Yes this appears to be a consensus after browsing many old threads on this subject- that the aftermarket Bosch caps are perhaps bottom of the m119 food chain which is unfortunately what I have new in my 500E.

Next time OE MB only or perhaps Beru for me.

 

[Bill Walsh]

I also experience this problem when I let the car sit for two weeks or so. It has happened the last three or four times. Each time the poor running starts after 10 or 15 minutes. In each occasion I only drove a short distance and when I reached my destination and parked the car it was still running poorly. Each time when I returned to drive the car, after letting it sit from one to several hours, it ran perfectly. Is it possible the warmth of the engine dried out the moisture while the car sat?

 

[Jlaa]

I also experience this problem when I let the car sit for two weeks or so. It has happened the last three or four times. Each time the poor running starts after 10 or 15 minutes. In each occasion I only drove a short distance and when I reached my destination and parked the car it was still running poorly. Each time when I returned to drive the car, after letting it sit from one to several hours, it ran perfectly. Is it possible the warmth of the engine dried out the moisture while the car sat?

Bill - I am surprised that this happens to you. We live in almost the exact same climate don’t we? Actually I am in SF west-side proper and IIRC tou are either in the peninsula or the East Bay, so if anything your climate is slightly warmer —- I have never experienced this issue with my aftermarket Bosch caps and my car has sat for many weeks at a time.

My garage, though, is heated. Yours?

 

[Bill Walsh]

I live in SF also in the Marina and my garage is not heated but maintains a similar temp as the house. I recently had new insulators installed but my caps have 30K miles on them.

 

[gsxr]

Bill, did the problem remain even with new insulators? Also, what brand are the caps / rotors with 30k?

Side note: The theory about the mystery liquid being oil, doesn't quite align with the problem going away after the engine reaching operating temp. Seems the oil residue should not be affected that much by temperature (and, never "dries out", either).

 

[195910]

Has anyone tried to detect the misfire using live data from Star? The ignition voltage and combustion duration can be viewed in live data.
In theory its should be possible to see a ignition voltage drop at the affected cylinders when the current is grounded to block

 

[gsxr]

Has anyone tried to detect the misfire using live data from Star? The ignition voltage and combustion duration can be viewed in live data.
In theory its should be possible to see a ignition voltage drop at the affected cylinders when the current is grounded to block

Yes, when the problem is present and the misfire is consistent, the voltages are typically double normal on the affected cylinders (~60 instead of ~30 on the SDS voltage indicated). This usually helps pinpoint the left vs right distributor cap, or in some cases, particular cylinders.

I've never seen the SDS indicated voltages drop, I've only seen it spike when the misfire occurs.

 

[Eno]

Since we are talking about insulators, these are original insulators from my 1991 500E Bornite Metallic.
I will replace them as there are fine cracks on them but cannot be felt by hand.

 

[linjam]

Interesting thread. Thanks. I have had to replace my caps and rotors 3 times in the last 4 years. The problems usually arise after I have been away for a while, and the car has been sitting. The most recent time was a couple of months ago. When I started the car cold, everything was fine, but when it heated up, I would begin to have misfire issues. This time, my mechanic suggested also replacing the insulators, which were the original insulators. His theory was that old insulators develop fine cracks and hold moisture. So, I have recently replaced the caps, rotors and insulators.

When he replaced them, my mechanic noticed also that the camshaft seals were leaking slightly, so I've ordered new cam seals and will replace this week. Could there be a connection between leaky cam seals and misfiring? This fellow seems to think so. Apologies if this has already been posted somewhere else:

 

[emerydc8]

FWIW, I live in a very dry climate and I've never had a misfire problem caused by insulators or rotors/caps in 20+ years of M119 ownership, although I've changed them in the process of troubleshooting other idle problems. I have changed the cam seals on both cars too. One car was leaking oil fairly badly but this did not have any apparent effect on the engine. So the oil can be there and still no misfire (see pic). Maybe an oil + moisture combination will cause the problem as has been stated by several people.

 

[gsxr]

Interesting thread. Thanks. I have had to replace my caps and rotors 3 times in the last 4 years. The problems usually arise after I have been away for a while, and the car has been sitting. The most recent time was a couple of months ago. When I started the car cold, everything was fine, but when it heated up, I would begin to have misfire issues. This time, my mechanic suggested also replacing the insulators, which were the original insulators. His theory was that old insulators develop fine cracks and hold moisture. So, I have recently replaced the caps, rotors and insulators.

This has been discussed in the past. Klink said that cars which previously required new caps+rotors every 6-12 months, would stop "killing" caps+rotors if the insulators were replaced. It's a good chance your problems will go away for a much longer time now that all three components have been replaced. I don't think cracks have anything to do with it, but nobody has proved any of the various theories, yet.

When he replaced them, my mechanic noticed also that the camshaft seals were leaking slightly, so I've ordered new cam seals and will replace this week. Could there be a connection between leaky cam seals and misfiring? This fellow seems to think so. Apologies if this has already been posted somewhere else:

If the cam seals are actually leaking, there's a faint possibility it could be related to the misfire. However the cam seals rarely leak. Mechanics find thick liquid on the back of the insulators and may think this is oil from the seals. I'm not convinced this is true. When the cam seals leak, oil pours out the bottom and it's VERY obvious. This leak is so rare you'd have trouble finding photos of it on the forum, I think I've only seen it once or twice in over a decade?

 

[Russell R Coe]

JC220, very clever indeed.

I'm going away for 6 days in a couple of weeks.

I will pull the caps prior to leaving, and take some photo's. I will Reinstall them untouched. When I return on the 7 day pull them off again and see if there is any difference.
I will report my findings.

Here are my finding after letting the car sit for 5 days.

In the first five photo's are pictures I took after driving the car for five days straight on a 8 mile commute each way. You can see the Caps and rotors very dry. The last two pictures are off just the left front rotor and cap after the five days sitting. Amazing that so much moisture could build up in such a short time. I wiped the cap and rotor as dry as possible in the short amount of time I had. The car ran some what better, but was still lumpy and hesitant. So the big question is where is the moisture coming from?

 

[Bill Walsh]

Bill, did the problem remain even with new insulators? Also, what brand are the caps / rotors with 30k?

Side note: The theory about the mystery liquid being oil, doesn't quite align with the problem going away after the engine reaching operating temp. Seems the oil residue should not be affected that much by temperature (and, never "dries out", either).

Dave,, yes the problem occurred after replacing the insulators, I don’t know which caps and rotors were used at the 90K service but I’ll find out and let you know.

Bill

 

[linjam]

If the cam seals are actually leaking, there's a faint possibility it could be related to the misfire. However the cam seals rarely leak. Mechanics find thick liquid on the back of the insulators and may think this is oil from the seals. I'm not convinced this is true. When the cam seals leak, oil pours out the bottom and it's VERY obvious. This leak is so rare you'd have trouble finding photos of it on the forum, I think I've only seen it once or twice in over a decade?

Thanks, Dave. Yes, my mechanic, Marv, says the cam seals are definitely leaking but not horribly. I'll have them replaced in the next week.

I should add to my above post that each time the car had the misfire issue, I had just returned from an extensive trip of at least a week or more, AND during my absence, their had been an above average amount of rain and humidity.

Perhaps after reading all this and combining with my experience I should surmise that oiliness behind the old insulators combined with high humidity and the car's sitting for a week or more is a bad combination.

 

[Stevester 500E]

What variable about a bad cap is killing the cap-rotors?
A good cap with a good seal allows moisture to get into the cap.
So, is it safe to say that "water" vapor isn't a variable in this pesky issue?

This has been discussed in the past. Klink said that cars which previously required new caps+rotors every 6-12 months, would stop "killing" caps+rotors if the insulators were replaced. It's a good chance your problems will go away for a much longer time now that all three components have been replaced. I don't think cracks have anything to do with it, but nobody has proved any of the various theories, yet.



If the cam seals are actually leaking, there's a faint possibility it could be related to the misfire. However the cam seals rarely leak. Mechanics find thick liquid on the back of the insulators and may think this is oil from the seals. I'm not convinced this is true. When the cam seals leak, oil pours out the bottom and it's VERY obvious. This leak is so rare you'd have trouble finding photos of it on the forum, I think I've only seen it once or twice in over a decade?

 

[gsxr]

A good cap with a good seal allows moisture to get into the cap.
So, is it safe to say that "water" vapor isn't a variable in this pesky issue?

The seal on the insulator is more of a dust seal / vibration damper, IMO. The cap itself is vented at the bottom so the seal doesn't keep air or moisture out.

I still don't know why new caps+rotors seem to "fail" quickly on some cars, when used with old/original insulators, and then the same car stops eating caps+rotors when new insulators are installed with (another) pair of caps+rotors. Maybe Klink has some theories.

 

[Stevester 500E]

What do you guys think of this solution?

 

[gsxr]

That guy glued his cap to the engine? And then used dielectric grease (which is an insulator, not a conductor!) on the ELECTRICAL connections, 6:00-6:50?

Wow. I did chuckle at the "German torque spec for Japanese truck".

 

[MCR01]

If anyone has access to good quality laboratory scales it would be interesting to know whether baking the caps (or insulators) does actually result in a weight loss. If the caps/insulators do have moisture in their structure then baking them for a few hours at ~70C should result in an obvious weight loss, but you'll need accurate scales able to measure down to thousandths of a gram.
Dave Walsh

 

[linjam]

If the cam seals are actually leaking, there's a faint possibility it could be related to the misfire. However the cam seals rarely leak. Mechanics find thick liquid on the back of the insulators and may think this is oil from the seals. I'm not convinced this is true. When the cam seals leak, oil pours out the bottom and it's VERY obvious. This leak is so rare you'd have trouble finding photos of it on the forum, I think I've only seen it once or twice in over a decade?

I stand corrected. After speaking with my mechanic, it is not the cam seals which are leaking but the cam solenoids/magnets further over. He says the oil/liquid can migrate to the edge of the caps only. Can it from there, due to heat, become airborne and coat the inside of the caps or affect the insulators? No clue

 

[gsxr]

I stand corrected. After speaking with my mechanic, it is not the cam seals which are leaking but the cam solenoids/magnets further over. He says the oil/liquid can migrate to the edge of the caps only. Can it from there, due to heat, become airborne and coat the inside of the caps or affect the insulators? No clue

Leakig solenoids/magnets is VERY common. There is an excellent HOW-TO thread showing a re-seal procedure, but the simple fix is to replace them with new. This particular leak puts oil at the very bottom of the cap edge, near the vents/slots. Normally I wouldn't expect the oil to travel upward and end up only behind the insulators, but given the bizzaro nature of this issue, nothing would really surprise me anymore.

 

[Bill Walsh]

Dave,, yes the problem occurred after replacing the insulators, I don’t know which caps and rotors were used at the 90K service but I’ll find out and let you know.

Bill

Dave,

The caps and rotors are Bosch and were replaced 30K miles ago

 

[195910]

Gentlemen,

Has anyone bought M-B caps this year? any comments on the quality / moisture condensation.

Red baron occasionally coughs with the 2018 Beru caps (developed blue/white corrosion on the cap to rotor leads!)
But runs like new when refitted with the old 1996 distributors :S

 

[gsxr]

Red baron occasionally coughs with the 2018 Beru caps (developed blue/white corrosion on the cap to rotor leads!)

Have any photos of the corrosion...?

 

[195910]

Here are both old and new distributors.

- New BERU (2018 Production fitted excatly 1 year ago) with only 3000km, showing oxidation on the poles with white and blue-ish residues. thin cases on the poles were flaking off as well. There was condensation on the surface when I removed them.

- Old 1996 distributor (from the 1998 brabus conversion), had 113tkm, when removed it showed black carbon residues on poles and yellow powder traces from the coil pole to the spark plug poles. Poles were obviously pitted but Cylinder 1 pole (Green arrow) was worn the most and so this distributor was not serviceable.

Both were from the right bank (cylinder 1). But I now fitted the old 1996 left bank distributor in place. Perfect readings all around,

The question is, will we have the same issue with a new set of M-B distributors? need to know if the parts were updated.