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HOW-TO: Replacing M119 Distributor Insulator/Dust Cover

LWB250

"But - but - he'll see the big board!!!"
In my ongoing quest to sort out the 400E I recently acquired, one of the issues I noted in my initial inspection was a severely worn/damaged distributor insulator on the right distributor. While this typically does not prevent the car from running, in the climate I live in (west central Florida) the presence of humidity and dampness can affect the M119 distributors to the point of preventing the car from starting or cause it to run quite poorly. I had previous experience with an M119 equipped W140 that if parked for more than 4-5 days would idle and run poorly until the engine was warmed up enough to drive out the condensation that would accumulate in the distributors. Having intact insulators goes a long way to keep the distributors sealed from dirt, dust, oil and condensation.

If I was to rate this job on a scale of 1-10 for a competent DIY'er I would say it's maybe a 3 or 4. Nothing terribly difficult, but it does require some careful work to avoid damage to fasteners, areas in which I will point out.

Tools Required:

3/8" ratchet with short (3"-4") extension
3/8" drive 5mm hex bit
3mm hex wrench or ratchet bit if you have one
Paper towels or shop rags
Brake cleaner or cleaning solvent

Part(s) Required:

1 or 2 distributor insulators/dust shields - Mercedes 119 158 01 88 or Bosch 1230500240 (verify part numbers with the EPC or dealer using your VIN)

New insulator4.jpg


1.) Begin by removing the plastic cover over the distributor and spark plug cables. There is a tab at the lower edge towards the outside of the engine you must release to lift the cover off. This is often broken or missing.

Distributor cover.jpg

2.) With the cover removed, locate the three 5mm socket head cap bolts that hold the distributor cap in place. Using your 3/8 ratchet, short extension and 5mm driver, loosen all three bolts. They are captive in the distributor cap, so they can't be removed nor will they fall out. Due to the difficulty getting the ratchet drive and extension through and around the spark plug cables, I prefer to break the bolts loose with the ratchet then use a long 5mm hex wrench to spin them loose.

Distributor cap bolts.jpg

3.) With the distributor cap carefully removed and moved out of the way, get your 3mm driver and loosen the three 3mm bolts on the distributor rotor. NOTE: DO NOT use a "ball end" hex driver for this! It will almost certainly strip the sockets in the bolts. I prefer the "tap and snap" approach to these - get your hex wrench inserted in the bolt head, tap the wrench a few times to make sure it's firmly seated in the recess, and "snap" the wrench to break the bolt loose. These bolts are captive as well, so you can't lose them and they won't fall out. Once loosened completely, remove the rotor and place it out of the work area.

Rotor.jpg

4.) With the rotor removed you will see the rotor drive. In the center of the rotor drive is a 5mm socket head bolt. Using your 5mm bit and ratchet, loosen and carefully remove the bolt. Note that there is a flat washer under the head of the bolt. It may not come out with the bolt and remain in the recess where the bolt was located. Retrieve it as necessary and place on the bolt.

Rotor drive.jpgRotor drive bolt.jpg

5.) Carefully grasp the rotor drive and wiggle/pull out on it. It may be tight, so be patient and work it over. I like to use a set of instrument cluster hooks to pull this out. When it comes out make note of the position of the drive and the notch in the back of it, as this will need to index over the two pins on the drive when you install it.

Rotor drive 2.jpgRotor drive 3.jpg

6.) With the rotor drive out, you can lift the distributor insulator out of the recess. Once you do so, get a shop rag or paper towel(s) with a solvent or cleaner and wipe the area clean. If you're lucky the seal behind the distributor will be intact and there will be little dirt or oil in this area.

Old insulator.jpgDistributor housing.jpg

7.) With the area clean, place the new insulator in the distributor housing. There is nothing that holds it in place other than the rotor drive.

New insulator.jpg

8.) Taking note of the pins on the distributor drive, place the rotor drive on the distributor drive and start the 5mm socket head bolt. The rotor drive can only go on to the shaft in one position, so fit it carefully and check to make sure it is fixed in place. Run down the bolt and torque to a value of approximately 9 Nm. NOTE: I prefer to use thread locking compound (LocTite (blue) or equivalent) on this bolt. The torque value is relatively low, and you certainly don't want it rotating out while the engine is running.

Rotor drive.jpg

9.) Replace the rotor and tighten the 3mm bolts. I also advise the use of thread locking compound on these bolts as well. Be gentle here, there's no reason to do the "strong man" approach on these, it's not necessary and will make it that much more difficult for the next time you have to remove the rotor.

Rotor.jpg

10.) Carefully position the distributor cap over the distributor and rotor, and tighten the bolts.

Distributor cap bolts.jpg

11.) Replace the plastic cover over the distributor and spark plug cables. Take note that there is a "tab" that slides into a slot near the center of the engine on the cover. This anchors the inboard edge of the cover. The outboard edge will slide into the bottom half of the cover and latch on the tab that projects out from it. Congratulate yourself on a job well done and enjoy a cold beverage of your choice.

Distributor cover.jpg


Note that I took photos as I assembled the distributor, so the new insulator is present in the disassembly photos. Sorry for any confusion this might cause. To give you an idea of how bad one of these insulators can be, I have included photos of the old insulator below. Not only was it cracked and full of holes, the sealing ring had at least one split in it.

Old insulator2.jpgOld insulator3.jpgOld insulator1.jpg

If you have corrections or additions to this, please let me know and I'll update the post.

Dan
 
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gsxr

.036 Hoonigan™, E500E Boffin
Staff member
Fantastic write-up, and an epic first (!) post. Glad to have you abaord, Dan! Don't worry, we won't judge you by the stories Kaleb told us... :D

:welcome4: :welcome3:
 

gerryvz

Site Honcho
Staff member
Properly done and direly needed HOW-TO, indeed. Thank you for the contribution.
 

lowman

E500E Resto God, Hierarki-Man
If you are using the correct tightening torque..the bolt will NOT come loose...so..NO thread lock on the bolt holding the rotor bracket...and 9 NM is the proper torque :)
 

gsxr

.036 Hoonigan™, E500E Boffin
Staff member
If you are using the correct tightening torque..the bolt will NOT come loose...so..NO thread lock on the bolt holding the rotor bracket...and 9 NM is the proper torque :)
It can come loose, and if it does, you will see something like the photos below. If you're really lucky, it will happen when you are 600 miles (1000km) away from home and spare parts, as it did for me.

A dab of blue threadlock is cheap insurance. Highly recommended. There is no downside to using the threadlock.

:gsxrock:
 

Attachments

lowman

E500E Resto God, Hierarki-Man
It can come loose, and if it does, you will see something like the photos below. If you're really lucky, it will happen when you are 600 miles (1000km) away from home and spare parts, as it did for me.

A dab of blue threadlock is cheap insurance. Highly recommended. There is no downside to using the threadlock.

:gsxrock:
I have to disagree . When tightened with the proper torque ,it can't come lose .it does not come loose when from factory . But with the variables of many people working on the car ,you never know of course .but go ahead and thread lock the thing.I won't
 

gerryvz

Site Honcho
Staff member
IMHO, a drop of blue threadlocker is a prudent solution. I realize that it's quite an extensive process to source the threadlocker (the stuff's darned hard to find!), and to place a drop on the threads of each of the rotor bolts. But I think it's worth the serious hassle and effort to do so, as an insurance policy.

Next thing you know, some wag is going to recommend using Hylomar on the insulator instead of the o-ring. DON'T.

Sigh.....
 

nocfn

E500E Guru
I actually got bolts from MB for my steering coupling and they were torx instead of hex, but had bubble of blue Loctite, and a specified torque spec.
 

lowman

E500E Resto God, Hierarki-Man
I actually got bolts from MB for my steering coupling and they were torx instead of hex, but had bubble of blue Loctite, and a specified torque spec.
Then its okei.They put on the threadlock for a reason.:)

Maybe someone should order the bolt for the rotor bracket ..so we can have a look if its threadlocked :)Maybe Jlla would want one for his massive spares collection for the future ;) :hugs:
 

mercepor

Member
I have just changed my caps, rotors, insulators. I bought a set on ebay
https://www.ebay.de/itm/Bosch-Verteilerkappe-Cap-Rep-Kit-for-Mercdes-R129-W140-W124-400-420-500-AMG-60/173072797109?epid=1514558631&hash=item284bf14db5:g:DJMAAOSwB09YJNmW

Interestingly, the rotors were not fit perfect to the drives. Inside the rotors two part of the plastic made a gap between the rotors and the drive.

I had to grind to level. Not funny to adjust a new part......

Anyway, now it is good, but strange to have new parts like this.
 

Attachments

mercepor

Member
Btw, the old insulators look very good, they are from 1991, the originals, The new are from 1996, not sure they are better.....

IMG_20160908_205104.jpgIMG_20160908_205055.jpg
 

lowman

E500E Resto God, Hierarki-Man
Btw, the old insulators look very good, they are from 1991, the originals, The new are from 1996, not sure they are better.....

Would definetly keep them .clean them up proper..put new O rings on them..and good to go :)
 

LWB250

"But - but - he'll see the big board!!!"
There was a change in the distributor drives on M119 engines at one point that required the rotor "bracket" (the metal part the rotor bolts to) to be replaced with an upgraded/redesigned part. I wonder if this was the issue with your engine? I believe the change took place around 1992. Original bracket was a 119 158 04 40 and the updated bracket was a 119 158 06 40, I believe. I never knew what the difference was, but I'm sure someone here knows.

Dan
 

lowman

E500E Resto God, Hierarki-Man
I have just changed my caps, rotors, insulators. I bought a set on ebay
https://www.ebay.de/itm/Bosch-Verteilerkappe-Cap-Rep-Kit-for-Mercdes-R129-W140-W124-400-420-500-AMG-60/173072797109?epid=1514558631&hash=item284bf14db5:g:DJMAAOSwB09YJNmW

Interestingly, the rotors were not fit perfect to the drives. Inside the rotors two part of the plastic made a gap between the rotors and the drive.

I had to grind to level. Not funny to adjust a new part......

Anyway, now it is good, but strange to have new parts like this.
its because you have OLD STOCK / first version of the rotor bracket.and the rotor you ordered are the LATE type..which only fits late type rotor bracket.
The surface of the rotor bracket is totaly flat on the rotor bracket on your pictures..which is a sign of beeing the first version.which has parts number A1191580340/ and this beeing superseeded by A1191580440(which is still the same rotor bracket,as far as i understand the Epc writing
These can only be used with rotor parts number 119 158 01 31 :)

That is why it does not fit :)

First version.Flat surface..




late version,,with the 0640 parts number
 
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gsxr

.036 Hoonigan™, E500E Boffin
Staff member
I have just changed my caps, rotors, insulators. I bought a set on ebay
https://www.ebay.de/itm/Bosch-Verteilerkappe-Cap-Rep-Kit-for-Mercdes-R129-W140-W124-400-420-500-AMG-60/173072797109

Interestingly, the rotors were not fit perfect to the drives. Inside the rotors two part of the plastic made a gap between the rotors and the drive.

I had to grind to level. Not funny to adjust a new part...... Anyway, now it is good, but strange to have new parts like this.
There was a supercession on the rotor bracket, from p/n 119-158-04-40 to 119-158-06-40.

It's possible that you have the early part number. I've never heard of a rotor not fitting properly, and this is the only explanation I can think of...

EDIT: Looks like several of us were typing the same thing at the same time, lol.

:klink:
 

lowman

E500E Resto God, Hierarki-Man
There was a supercession on the rotor bracket, from p/n 119-158-04-40 to 119-158-06-40.

It's possible that you have the early part number. I've never heard of a rotor not fitting properly, and this is the only explanation I can think of...

:klink:

do you read stuff at all?
 

lowman

E500E Resto God, Hierarki-Man
Ok, I see. Thx for your help, I will go for old style rotors.
thx again
i think it would be a better bet to update the rotor brackets..as the early type rotors do not come up in any searches..at least what i found .The late type seems to be the one that is "available..like anywhere...?
 

mercepor

Member
i think it would be a better bet to update the rotor brackets..as the early type rotors do not come up in any searches..at least what i found .The late type seems to be the one that is "available..like anywhere...?
Yes, i just realized that the easiest way would be the new style brackets.
 

Efraim

Member
Hello Guys,

The M119 is true well balanced V8! It will run smoothly even the other distributor is out of function, ie. 4 out of 8 cylinders deactivated.

I started to open and clean distributor cap and rotor as I noticed some misfiring during warming up phase.

When removed the plastic cover I noticed a crack in the distributer cover and there were some orange dust around. It turned out the cap is in pieces and the dust cover/insulator was totally grinded. Even one hex bolt of rotor was cut.

Prior opening I didn’t notice any major difference in behavior of the engine except the misfiring. When hot it ran smoothly, only very very minor rasping sound from the front right of the engine. No lack of power is determined since there were very slippery here in winter time while the ASR is limiting engine power constantly.

The distributor and rotor were Bosch parts replaced about three years and 13kkm ago. The dust cover is more than 13 years old. Perhaps the age of the cover is the major reason for the disaster. Or could the misfiring cause cap brittle? The rotor bracket was the new version (A119 158 06 40) so the mismatching of the parts were not the issue.

My lesson to learn:

  1. when replacing the cover always replace seal, rotor and the insulator cover.
  2. take any misfiring or abnormal sounds seriously and find to root cause.
 

Attachments

Jlaa

Active member
Wowowow. Thanks. I gather that you live in Finland — can you describe what kind of environment you car sees? Driven in inclement weather? Stored in climate controlled garage? Etc.

thanks
 

gsxr

.036 Hoonigan™, E500E Boffin
Staff member
Sooooo.... while I can't be certain, I have a very strong suspicion as to what happened here. It looks like one of your 3 rotor bolts came loose and fell out, and then rattled around inside, destroying the softer plastic of the insulator. The root cause was likely the bolt not being tight enough, or the lockwasher cracking and no longer locking.

This is why I install rotor bolts with a dab of blue Loc-Tite. I also apply blue threadlocker to the center bolt that holds the rotor bracket to the cam sprocket. I had a very similar failure years ago. In my case, both the center bolt on the bracket loosened up, and also 1 of the rotor bolts loosened enough to completely come out. In my case the loose rotor bolt flailing around destroyed the cap, rotor, insulator, bracket, and dowel in the cam sprocket. Pics below... of course, this happened while on a trip 600+ miles from home. Fun stuff.

:shocking:
 

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Efraim

Member
About weather in Finland. Here Cental South of Finland is quite typical for Scandinavia on this latitude. During winter time on January typically -10C - -3C (14F- 27F) and on summer time (Jul) from 15C - 25C (39F-77F).
I tent to avoid driving then when there is the worst slush condition and salt on roads. The fresh snow (about -10C) with sun shine is one of the best weather when I like to take car out. Then there is very low water concentration in the air.
The car has good home to live as it’s always kept in warm garage (about 10C, rel. hum 50% during heating season, I have air drying there) that is not common. The most of cars in Finland are kept all the time outside including MB’s without major problems. Sometimes my heart broke when seeing a new MB in below 20cm snow layer with -20C.
It’s hard to know how much the case is due to climate, as I we have red here that the misfiring is taken place also elsewhere. In my mind it was just time that cracks the insulator cup the first causing the case. But for misfiring the short driving periods may be one reason as the distributor will not have enough time to heat and dry.

----

The loose parts was not the case here. Rotor and the bracket was solid although one rotor bolt was cut. I also considered using Loctite for bolts but didn't apply as the bolt and nuts are quite weak and there were tight even after the grinding.
 
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samm

Member
Hi there,

a general info tip that worked for me regarding removal of the rotor bolts (the three M5 bolts [with 3mm socket head]).

The bosch ones always seem to lose their shape. SO what I did when installing new ones was to use this:

https://www.ebay.com/itm/Vibra-TITE-470-DriveGrip-Anti-Cam-Out-Fluid-15mL-Tube/202510668110

https://smile.amazon.com/Vibra-TITE-470-DriveGrip-Anti-Cam-Fluid/dp/B008RMT63A/


It definitely helped me tighten them without chewing up the allen shape in the bolt.

I then had to remove the rotors again so I reapplied some on the bolt so I could remove them easily. It worked for 5 out of the 6 bolts. The 6th one needed a small torx piece held by a pair of clamp pliers which then got hammered into the bolt, just so that I could turn the bolt to loosen it.

Remember if you ever do use this make sure you wipe it off the bolt. Don't leave it on the bolt because it will fly around your distributor cap.

If anyone knows the spec for stronger rotor bolts please let me know, would be much appreciated!
 

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gsxr

.036 Hoonigan™, E500E Boffin
Staff member
If anyone knows the spec for stronger rotor bolts please let me know, would be much appreciated!
There was discussion on a separate thread, but the solution I settled on was using OE rotors made by Doduco, which have bolts with proper-sized socket heads. No sloppy fit with a 3mm Allen wrench / hex driver. I have no idea why all the Bosch rotors have "oversize" socket heads that love to strip out.

Another option is replacing the Bosch bolts with something that has a 4mm socket head - details are in this thread.

:sawzall:
 

samm

Member
I want some bolts for my recently installed bosch rotors.

I'll likely pick up some Beru rotors in a couple weeks when I got to London.
 

Efraim

Member
Tar spray is one option for locking bolts. It's making the surface sticky but still prevent stucking. This was invented by timber truck drivers whos wheel bolts tend to get loose under heavy load. I don't know if this nice smelling magic product is avalable outside Finland & Scandinavia.

EDIT: After second though I would not recommend tar for hot parts as in higher temperature it’s not sticky anymore.
 
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