103 300E 1986 Distributor cap: O-Ring seal location?

[azurite300E]

I just finished replacing the spark plugs, cables, distributor cap/Suppressor Housing, and rotor. I also purchased separately the distributor cap O-Ring seal (because it was shown next to the cap on the parts catalog) but could not see where it has to go. When I took off the old cap there was no O-Ring anywhere to be seen, and no, I did not just drop to the ground without my knowledge. On the other hand I checked job No. 15-3010 of the MB W124 shop service manual that describes the replacement of the distributor cap and rotor, and there is no O-Ring shown explicitly as a separate part of the assembly diagram either.

The new O-Ring is brown in color, very similar to the cap's color, but on the car the closest I saw to it is a black/dark flattened seal mounted on a groove on what the catalog calls the "suppressor cover" (called "sealing washer" (3) in the MB manual) which is a round yellowish plate that turns freely and is mounted behind the rotor. I could not remove it because the rotor follower/adapter (the metal part where the rotor is mounted) needs to be pulled with a special removal tool which I did not have on hand. This "seal", although about the same diameter of the new O-ring, is very stiff, not flexible like rubber, it feels more almost like plastic. I gently tried to pry it off the groove for inspection with a small screwdriver, but it would not even move or stretch, so I left it alone for now to give me time to research the matter before proceeding any further.

Can someone confirm that this is the correct location of the distributor O-ring seal? Maybe that stiff seal that I see now are the remnants of the o-ring that have stiffened over the years because of the hot/cold engine cycles. Since the old seal will most probably be destroyed or at least damaged during removal, I just wanted to make sure I'm on the right spot.

Thanks.

[Ferdman]

The O-ring fits on Item 3 (suppressor cover) in your diagram. As I recall you'll need to remove the steel hub that the distributor rotor mounts to in order to remove the orange suppressor cover, then R/R the O-ring. The hub is keyed so it only fits on the cam shaft one way.

[azurite300E]

Thanks Fred, I suspected that. I think I'll be able to pry it off from the suppressor cover without removing the rotor carrier, as I don't have the appropriate tool to remove the carrier. The old o-ring will probably be destroyed in the removal process since it hardened, but now that I'm sure it really doesn't matter. Maybe I just carefully cut into it with an x-acto knife so afterwards it will be easier to remove by just pulling it off from one of the ends.

In hindsight it probably would have been best to just replace the suppressor cover which already comes with a fresh o-ring attached.

-Alex

[think300E]

Is it necessary to swap this O-ring when replacing the dist cap? I wasn't able to find it locally, so I had to order it from peach parts (actually allpartsexpress).

If the O-ring is not craked, can it just be left alone? Otherwise, I will probably need to do the same thing azurite300E mentioned - to carefully cut it and try to pry it... no telling if one risks the chance of breaking that supressor cover.. someone local said they would sell it to me at their cost (which is about $60) quite a lot.. when the O-ring runs about $5

My dist cap/rotor is not set to arrive until Wed, not sure when the O-ring will arrive.

Thanks

[Ferdman]

think300E, replacing the O-ring is optional. If it's old and brittle best to replace it. A small pick should help to remove the old O-ring, but installing a new O-ring with the supressor cover in place may be difficult due to the tight quarters.

As I recall you need a Torx bit to remove the rotor hub.

[think300E]

Thanks I was able to RR the distributor cap and rotor and left the O-ring as is.. it was not brittle (it was hard, all in one piece so I left it as is) didnt want to chance breaking the suppressor cover.