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

[gsxr]

Last I recall, even the OE MB dealer caps are plain Bosch without the clearcoat applied... same as aftermarket Bosch. However, I've never bought a pair of OE caps so I'm not sure if this is accurate. And, if you were able to obtain some old stock caps, they may still have the clearcoat applied, even if current production does not.

Very odd that such minor oxidation on the Beru caps actually caused misfiring. Those look OK visually to my eyes.

 

[195910]

Here is a better shot, focus on cylinder 1

 

[gsxr]

Was that causing a misfire under load, or at idle, or both...? Only only cylinder #1?

 

[nocfn]

FWIW, my Dad's E420 MY94 had a chunk of missing insulator, and enough corrosion to grow corn in the DS dizzy cap. Idle and load smooth as butter. go figure.

 

[JC220]

There was condensation on the surface when I removed them.

This moisture was your primary problem I think. I bet the same caps dried out would run OK again.

Are the insulators new or original? Did you remove and clean them behind yes?

 

[195910]

Hi Dave,

It was a few small things causing all sorts of misdiagnosis.. But finally Solved!
Cold start is perfect, but let it idle warm and it will hiccup. I drive it 3-4 hours long distance and it never skips a beat, drives perfect with full power above 1800rpm, no misfire when driving even at high speed.

I was getting short to block because of the higher resistance at warm idle, with the ignition voltage occasionally deciding to take the easier route. Could not be traced with LH& EZL live data, Till I found out where it was all going (thanks to a technician in the US). Now I can see the distributor issues live.

Conclusion 1: never trust anyone's work and never trust any new part you did not fit yourself.

 

[195910]

This moisture was your primary problem I think. I bet the same caps dried out would run OK again.

Are the insulators new or original? Did you remove and clean them behind yes?

Replaced both with new old stock Bosch (affraid of anything new), one of the old ones had a hairline crack right across.
The back was clean, did not see oil staining and I don't believe it oil, more like moisture.

 

[gsxr]

Did you have new insulators installed with the Beru caps, and still had the warm idle misfire with new insulators?

 

[195910]

Did you have new insulators installed with the Beru caps, and still had the warm idle misfire with new insulators?

Yes!
I am going to start a new thread with a video of the idle now this weekend. This must have been one of the most difficult diagnosis ever on a M119, even chief engineer of Brabus looked into it a few months ago.

 

[gsxr]

Wow! Would love to know what you did to finally diagnose this - what tools used, etc.

 

[gsxr]

Oh, btw... forgot to ask before. What brand + model (part number, i.e. F8DC4) spark plug are you using in the Brabus 6.5 motor...?

 

[195910]

Oh, btw... forgot to ask before. What brand + model (part number, i.e. F8DC4) spark plug are you using in the Brabus 6.5 motor...?

The 6.5 uses the same spark plugs as the 6.0L. Bosch F7DCO or NGK.. I bought a set from M-B part number A0031591603
We have the spark plug spec on the Brabus plate fitted to the can bus cover.

 

[gsxr]

Cool. I'm using the F7DCO and NGK equivalent in my 6L as well.

 

[JC220]

On my S500 coupes replacement m119 motor I am renewing all seals in the engine. All except the head gaskets that is.

Note that the original seal rings behind the distributor rotor arms feel quite hard. The new seal rings feel nice and supple in comparison and I am glad I am changing them when comparing old and new side by side.



Sorry for no cap vent mod updates on my 500E. My S500 coupe will be the participant now since it will hopefully soon be running and used as a weekend driver through winter. That will be perfect for the moisture scenario VS my 500E which is soon to be tucked away for winter and wouldn't give useful data.

 

[LaugeR129]

On my S500 coupes replacement m119 motor I am renewing all seals in the engine. All except the head gaskets that is.

Note that the original seal rings behind the distributor rotor arms feel quite hard. The new seal rings feel nice and supple in comparison and I am glad I am changing them when comparing old and new side by side.

Do you have a part number for the seal rings? I can't seem to find them in the EPC, so a part number would be much appreciated!

 

[ricsim]

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.

Have you notice that a ventilation hole is missing on the beru's distributors ?

 

[gsxr]

There's no ventilation holes in those locations (inside terminals) on any caps, when new. Close-up photo attached of a new Bosch cap.

 

[ricsim]

This hole doens't exist on the beru's cap (green circle in the picture)

 

[gsxr]

This hole doens't exist on the beru's cap (green circle in the picture)

Correct! Photo below of both side by side. I don't think that one slot will have any significant difference though...

 

[J. M. van Swaay]

For what it’s worth, I live in a hot humid climate (Florida Keys) and I have had to dry the insulator rings three times in the last six years. The problem usually occurs when the car is not driven frequently and we have high humidity with significant day/night temperature variations. It is very obvious to me that condensation is forming on the inside of the insulators. Originally, I thought I needed to replace ignition parts..... now, I just consider drying the caps rotors and insulators routine maintenance kinda like changing the oil...

 

[Kyiv]

I just consider drying the caps rotors and insulators routine maintenance kinda like changing the oil...

I'll plant another anecdote on the topic. My Bosch caps and Bosch rotors are 2 years/~20k mi old and insulators are 5 years ago/~25 k mi old. Car has been driven, more or less, daily during past 2 years, although several times it was left parked in the driveway (no garage) for 1 or 2 weeks, when I was away. No drivability issues, even though Virginia is pretty rainy and humid. In July I left for vacation, 10 days. Came back for 3 days - car drove fine. Left again for a week+. Drove the car upon returning and soon after coolant reached operating temperature it started driving like crap, power cutting in/out, and backfiring. I knew what it was right away. I started limping home, but in about 4-5 minutes it cleared by itself and hasn't returned for 3 days now. I assume the moisture got evaporated , but I placed a necessary hex to unbolt rotor caps into the trunk

 

[Kyiv]

Just sharing. I finally drove my car today after it has sat for about 5.5 months for winter + delays for some work. It fired right up, but started to miss and hiccup here and there once it warmed up, but not too bad. I of course knew what it was (moisture in a distributor). 30 minutes of driving and it cleared up and hasn't returned over the next hour or so of driving. A few restarts + a short 15 min drive a few hours later - no issues.

 

[gsxr]

@kiev, have you tried adding the slots to the caps, as mentioned in other threads?

 

[gerryvz]

You should cut the @robm.UK grooves into your caps.

 

[Kyiv]

@kiev, have you tried adding the slots to the caps, as mentioned in other threads?

You should cut the @robm.UK grooves into your caps.

I did not need to yet. For the 2nd time over the last 2 or so years, where moisture has accumulated due to car's extended standing, driving it relatively aggressively clears things up after 30 or so minutes. I did not have to remove distributors for wiping.

And it seems that one such clearing drive is enough. This morning, despite humidity in the 80s, no issues after 2 restarts. Last time was a a year ago in VA, where humidity was in the 80s all the time, one 30 min drive after about 2 weeks of car parked in the driveway in torrential rains, was enough to clear for good

 

[sheward]

This seems to be the very same degree of occurrence present with my car while I am working on it over extended periods with limited starts. It always starts fine, exhibits some minor misfiring after warm, and then clears up and has no issues if driven regularly. I plan to add air slots to the caps when I remove to inspect.

drew

 

[gerryvz]

@kiev ... if you cut the grooves into the caps, you won't have this problem in the first place, no matter how long the car stands.

My two cents.

 

[Duh_Vinci]

@kiev ... if you cut the grooves into the caps, you won't have this problem in the first place, no matter how long the car stands.

My two cents.

Did this about 3 months ago, no more moisture issues at all!

 

[tomer]

Hello all, I searched several threads and could not find this answer... I also have an annoying misfire at idle, with some oil residue in my caps and a little on insulator. I am about to remove the insulators this evening. My question is, where are the vents supposed to be placed?

I had my indie mechanic replace insulators/rotors/caps/wires and plugs a year ago, with sadly very little mileage on it (like 300 miles...) They oriented the vent slots at about 10 o'clock... I did note above Dave mentioned the vent slots should be at the bottom... The cap rim does not seem to have any installation slots so one can install it with the vent slots at ~ 10 o'clock, or ~ 2 o'clock or about 6 o'clock?

Lastly, my engine has oil leaks with plenty of crud on the block in the front area (embarrassing I know, will be working on this soon). with my cap vents at about 10 o'clock could oil residue be getting into the cap from my general messy engine?

thx!!
Tom

 

[gsxr]

The cap is keyed to only fit one way, always with the vents at the bottom. If you add vents they would be at the 10 and/or 2 positions. Although it appears the cap is symmetrical, it is not.

If you have oil leaks, those should be addressed first - I'll be posting more about this shortly.

 

[tomer]

That seems very logical! My Bremi caps have 7 vent slots, two groups of 3 and the 7th near a bolt hole, but nothing is cast into the cover and nothing else on the cap that would key the cap in a certain orientation.

 

[gsxr]

This seems to be an appropriate thread to add more data on the in-famous liquid-on-the-insulator problem.

One of my cars received new caps, rotors, and insulators along with new oil seals at the cam sprocket behind the rotor bracket. Several years but only 2500 miles later, I discovered the new insulator had a film of liquid on front & back. The insulators are new Bosch aftermarket without the clear coating. This was in the middle of summer with a 100F heat wave and humidity near single digit levels. It wasn't moisture. [Edit: It also was not WD-40 as this was never sprayed into these particular caps.]

But... the oil seals are new and there was NO trace of oil around the seal. HOWEVER! The cam solenoid/magnets have a slight leak (from the metal body, and/or the electrical connector). And there was a trace of engine oil running along the edge of the front head cover, at a ~45° angle, where the oil runs along the bottom edge of the distributor. The liquid on the insulator could not be water or moisture, and was definitely not oil vapor leaking past old radial seals. Also, there was oil at the lower edge of the distributor cap, near the bottom venting slots.


My latest theory: Oil leaking from the cam solenoids, hitting the bottom of the distributor cap, may be getting affected by the spark occurring ~1 inch away. Perhaps this is causing some oil to vaporize and deposit a thin layer of oil residue on the insulators, possibly inside the cap as well.

The question was always, "When these cars were new in the 1990's, they didn't have constant ignition problems - what changed?". The answer might be, in the 1990's, the cam solenoids had not started leaking oil yet. And since the solenoids/magnets almost never fail [electrically], and since many people ignore oil leaks not large enough to leave puddles on the garage floor, this MIGHT be a possible root cause for the blasted oil/liquid on the insulators.

FWIW, the car I described above had no misfiring or other ignition issues. I had the distributor taken apart while doing other work and discovered this by accident. I cleaned the film of liquid off the insulators and re-installed everything. I need to replace the cam solenoids to fix the small oil leak, as I don't have the time or patience at the moment (Sept-2021) for the re-seal procedure outlined in @JC220's excellent HOW-TO at this link. A proper re-seal would have the same result. EDIT: Solenoids were re-sealed in spring 2024, see Update #3 below.

@Klink ? If you're out there, do you have any input?

UPDATE 2: This car has been driven ~1000 miles over ~6 months [now spring 2022] and has had zero misfiring. I need to pull the caps again and see if there's any sign of liquid returning.

UPDATE 3: In spring 2024, this car had the cam solenoids removed, disassembled, and sealed internally with RTV per the instructions linked above. Full details in post #141 below.

 

[tomer]

At the risk of embarassing myself, would this be the cam solenoid which is clearly leaking? And the second pic shows the leak/crud doing down toward the distributor cap... And with my vent slots having been clocked at ~ 10 o'clock they would be ready to receive residue :-(

 

[gsxr]

Yup! The big round metal thing with wires connecting at the side is the cam magnet/solenoid.

If that is your car, the leak isn't too bad, but still should be remedied...

 

[tomer]

Indeed that is my messy power plant... Now where is my brake cleaner!!!

 

[ChrisH]

@kiev ... if you cut the grooves into the caps, you won't have this problem in the first place, no matter how long the car stands.

My two cents.

Slotted cap with “ Mercedes Mystery Goo” ( MMG ) after ~ 300 miles ! Any one with a gas chromatography unit in their shop What is the purpose of the pliable cover on some caps ( Bosch vs Beru ), My indie removed mine in an effort to improve the situation, it didn’t !
My bad, I reviewed gsxr’s images of caps and rotors and see the Beru also wears a prophylactic cover !

 

[nocfn]

I jut about ended that phenomenon by removing and replacing camshaft seals.. Did it in two different cars in two different climates and both are running great since. (been 11 months for one an 6 for another)

 

[gsxr]

Your goo in the photo looks like oil residue, which is very common in this specific area. See post #132 above.

 

[ChrisH]

I jut about ended that phenomenon by removing and replacing camshaft seals.. Did it in two different cars in two different climates and both are running great since. (been 11 months for one an 6 for another)

Here are the cam seals in situ. The passenger side looks a little weepy and indeed had the most accumulated goo/oil.
I have new seals to replace. I have the records on this car and the insulator cups were original with 94 cast in, so I’m assuming the cam seals are also original with 203 K miles. What do you think about the flexible cover on the distributor cap ? The weepy one won’t upload

 

[gsxr]

Your cam seal looks good, or at least is not leaking oil visibly.

The usual source is the cam advance solenoid, where coats the lower edge of the distributor cap with engine oil as it dribbles past.

Note sure which "flexible cover on the distributor cap" you are referencing? If you mean the top cover of the 2-piece cap, with 5 holes in it - don't worry about that, it shouldn't be related to any ignition issues.

 

[gsxr]

One of my cars received new caps, rotors, and insulators along with new oil seals at the cam sprocket behind the rotor bracket. Several years but only 2500 miles later, I discovered the new insulator had a film of liquid on front & back. The insulators are new Bosch aftermarket without the clear coating. This was in the middle of summer with a 100F heat wave and humidity near single digit levels. It wasn't moisture.

But... the oil seals are new and there was NO trace of oil around the seal. HOWEVER! The cam solenoid/magnets have a slight leak (from the metal body, and/or the electrical connector). And there was a trace of engine oil running along the edge of the front head cover, at a ~45° angle, where the oil runs along the bottom edge of the distributor. The liquid on the insulator could not be water or moisture, and was definitely not oil vapor leaking past old radial seals. Also, there was oil at the lower edge of the distributor cap, near the bottom venting slots.

Latest update on post #132 above:

The car referenced above was driving normally 99% of the time since the work performed in Sept-2021. This spring when fired up after 7 months of storage, it ran normally for a 25-minute test drive. But when parked for maybe 10 mins, after a restart it began misfiring.

For reference:

• Caps are Beru, 9 years old, but only 5kmi. NO vent slots cut.
• Insulators are Bosch, 9 years old, but only 5kmi. Visually perfect.
• Rotors are OE Doduco, 3 years old, 3kmi. Visually perfect.

I removed both caps for visual inspection. The driver side (left) looked good and was mostly dry. The passenger side (right) had visible moisture in the cap along with visible carbon tracks from arcing / misfiring. Yep, time to add the vent slots. Once again, the insulators had a thin film of liquid (NOT water) covering both front & rear surfaces. The aluminum head cover behind the insulator is bone dry on both driver & passenger sides. Since the cam solenoids were original and not replaced or resealed, there was still the small amount of engine oil present at the lower edge of the caps.

So, I installed re-sealed cam solenoids/magnets per @JC220's writeup (click here). Disassembled, cleaned, de-oiled, and reassembled the magnets with Permatex Ultra Black RTV (the super-oil-resistant stuff). Hopefully this will eliminate the trace of engine oil which keeps reappearing at the lower edge of the distributor cap. The cam magnets were installed with anaerobic sealant per the FSM. The head surfaces surrounding the cam magnets and distributors were carefully degreased to help identify any oil leaks in the future. It's all clean & dry right now.

The passenger cap looked pretty bad, but cleaned up nicely, as did the driver side. I cut the vent slots (per this thread) to improve ventilation and hopefully eliminate the misfiring due to water/condensation buildup 20-30 mins after a cold start. The rotors were fine and reinstalled as-is. The insulators had the film of unknown liquid wiped off with solvent and reinstalled.

I'm hoping this will cure the occasional misfiring permanently, assuming the engine oil leaks are 100% stopped. The added ventilation should prevent water/condensation from building up inside the cap, and the lack of engine oil should prevent the weird film building up on the insulator. I plan to take everything apart next winter while in storage (after a summer of driving/racing) to see if the insulators are still nice & dry, then monitor yearly after that.

I did pretty much the same thing on a different car (cut vent slots in the caps, eliminated oil leaks with new cam magnets, etc etc - photos here) and will monitor that engine as well. This is the first time I've replaced or resealed the cam magnets and I'm really hoping it will be the permanent fix for both cars. I also plan to re-seal more cam magnets and do the same job on other cars, it's just a PITA because the power steering reservoir has to come off to do this job.

Photos below, before & after. Note the engine oil visible at the bottom of the cap (at the vent slots) in the "Before" pictures.




UPDATE: At the end of the 2024 race season, there have been zero issues with misfiring. I'll continue to update over time to see how long the "fix" will last.

 

[emerydc8]

I also plan to re-seal more cam magnets and do the same job on other cars, it's just a PITA because the power steering reservoir has to come off to do this job.

Dave, are you reusing the power steering reservoir gaskets or installing new gaskets? The factory gaskets are expensive. The AutohausAZ gaskets are definitely more reasonable but they don't have the seal around the perimeter.

 

[nocfn]

Dave - UGH I had no idea you were encountering a similar rabbit trail. @emerydc8 I had resealed these things when I got the car and after 3-4 years the koala claw goo gave up. I just decided to bite the bullet and get new, along with the new style armature and new bolt as the manual says. They have been leak free for quite a while compared to resealed units. And during that time I had that reservoir off 4 times and on the 4th time, I replaced the gasket so that I would not have to do it again.

 

[gsxr]

Dave, are you reusing the power steering reservoir gaskets or installing new gaskets? The factory gaskets are expensive. The AutohausAZ gaskets are definitely more reasonable but they don't have the seal around the perimeter.

Jon, I've been re-using the power steering reservoir gaskets if they are in good condition / undamaged. I clean them off an add a smidge of Hylomar around the holes. So far this has been working fine.

The OE gasket price is silly at $37 list (~$30 discount), and all the aftermarket gaskets are NLA (link). Ignore the "temporarily unavailable" note, it's stated that for years. We used to be able to get CRP / DPH gaskets for $4 each. I have a couple of NOS DPH but don't plan to use them unless necessary. Next option would be cutting my own gasket from bulk material.

On a related note, while cleaning the threads for the 4 reservoir mounting bolts, one had part of the threads come out with the tap (!!). I substituted a longer bolt temporarily, which torqued to spec. Then, another bolt didn't torque to spec and felt like it was stripping... ugh. The remaining 2 were fine. I did not have a Time-Sert kit in stock to fix these, and had to get the car running again, so I left it alone for now. I plan to repair both with Time-Sert (click here) the next time the reservoir comes off. Never had this happen before! Torque spec is 8Nm and I was using a 1/4" torque wrench. Grrrrrr.

 

[gsxr]

Dave - UGH I had no idea you were encountering a similar rabbit trail. @emerydc8 I had resealed these things when I got the car and after 3-4 years the koala claw goo gave up. I just decided to bite the bullet and get new, along with the new style armature and new bolt as the manual says. They have been leak free for quite a while compared to resealed units. And during that time I had that reservoir off 4 times and on the 4th time, I replaced the gasket so that I would not have to do it again.

Louis, if applied correctly, the koala claw goo should last way longer than 3-4 years. I'd like to have tried to pinpoint the source of the oil, there are a few other places it could be coming from, including the larger M8 bolts that hold the front cover to the cylinder head. Or, if you just removed the original cam magnets and re-installed them with fresh goo... they may have been leaking from the 2 metal halves of the shell. Those need to be taken apart and filled with different goo inside (as shown here).

Anyway - good to hear your new-style magnets are leak-free! And yup, after multiple times taking off the p/s reservoir, a new gasket is a good idea.

 

[nocfn]

They were OE so I saw no need in delaying the inevitable since I was doing the short hose back in the day now that I think about it some and the cam seals so on and so forth.

 

[emerydc8]

I did not have a Time-Sert kit in stock to fix these, and had to get the car running again, so I left it alone for now. I plan to repair both with Time-Sert (click here) the next time the reservoir comes off. Never had this happen before! Torque spec is 8Nm and I was using a 1/4" torque wrench. Grrrrrr.

That’s an expensive tool for just one size, but since most of the bolts on our cars are either 6 or 8 it would probably be good to have. Too bad Harbor Freight doesn’t make a version.

 

[gsxr]

Yup - they are NOT cheap. However as you said, M6 and M8 (with an assortment of different-depth inserts) will cover the majority of needs on a 124. I already have the M8 kit for a previous fiasco years ago, but I had never purchased the M6 kit. Wish I had bought this in the past as now I have to take it all apart again to repair.

 

[gsxr]

Well I didn't need to wait long for an update! Within about 75 miles of driving, there is already oil residue at both electrical connectors. I had disassembled these, degreased the wires & metal female sockets, and replaced the plastic pin bushing housing (connector). And, the solenoid male connectors were bone dry when installed. I cleaned everything again, this time adding a small paper towel diaper below the connector.

I believe the magnet inside is not as "sealed" as people think it is. Somehow, oil is getting inside that and leaking out the connector. It may require heat from the engine to expand the oil and push it out. After I had re-sealed these, I set them vertically on the workbench, electrical connector downward, for several days before installation. One had a trace of oil dribble out, the other was mostly dry. So, there was definitely some amount of oil inside the electrical windings. But there's no way to open this up to clean it out!

I'm hoping it's a small enough amount of oil inside the windings that eventually it will go away. However, what I don't know is if the oil can still enter the "sealed" winding after we've encased it in RTV. If oil can still get inside, it will still get pushed out from heat / pressure / etc. Grrrr.

 

[Jlaa]

I found this discussion on distributor caps on a German forum. I don't read/write speak German at all (although @TimL does) but I used Google Translate. Note this gentleman talks about cutting slots AS WELL AS using a certain spray:



Unfortnuately, Amazon.de will not post this to me. Anyone have any ideas?