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Distributor Install Adventure - Questions/Experience

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'75 block, '83 E12 head


I am in the process of eliminating oil leaks from the distributor body and the distributor housing.



  • Old O-ring:  27-mm OD; 3-mm height; round profile (left in the photo below) appears to be a standard O-ring. 
  • Replacement O-ring (12118530508 as near as I can determine) (right in the photo below):  27-mm OD; 5-mm height; D-shaped profile.  

Problem:  O-ring fits shaft snuggly; however, it seems to be too fat/massive to fit into housing (new O-ring installed in the photo).  I cannot get the O-ring past the the opening of the housing - probably could if I used a BFH.  It will not go without brute force that  I am not willing to apply. 

Question:  Correct O-ring?  What is the solution if this is the correct O-ring?  Should I go to Ace and get a work-a-day O-ring and carry on?

I could not fine any FAQ posts re: this difficulty.





No numbers on body.  I do not know its history.  Does this distributor look familiar?  It's ID, type, application, year, etc?




I will confirm what many here have stated:  easy to remove and re-install, use only a gasket to reinstall*, always replace special washer-seal (12110002735), and make sure all openings and tunnels are open and clean*.

*Someone in past used rubber stuff (photo below), probably to "assure" a good seal.  However, small bits of the rubber found its way into the housing body passageways through which oil flow.



Regards and thanks,




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I haven't seen aftermarket distributors used on these cars, aside from the IE model.  Could it be one of theirs?


The section above the gear looks like it is added as a spacer, in order to use a VW length distributor body. 

Does it turn independently?


The difference in shaft length is a bit over half an inch.  (.550")


I measured the groove that the O-ring fits into and the OD in there is .880" with a width of .2".


The D shaped O-ring is the standard Bosch style.


It is nice that it has a roll pin, instead of a peened in solid pin.  You could punch that out and pull it apart pretty easily.  I'd be curious to see what's inside.


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I, too, thought it might be an aftermarket non-Bosch/BMW distributor.  Tonight I checked the parts notes that came with the car and I'll be damned...an IE distributor! You were correct!  Thank you for the prompt to initiate an investigation.  Now, I know my new O-ring is for a Bosch; I can use it on my tii.  Yes, there is a spacer and it does move quite independently and freely.  Off to find the proper O-ring.

Thanks again,


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My recollection is the OE o-ring is D shaped as well.  


I do remember it took a fair bit of steady downward pressure before it slid into place. Lube it up with a finger full of oil, 360 and in the groove as well, and then press the disty firmly into the housing. You might even have to give the ring a bit of persuasion with a finger poke, but once the ring starts into the housing it slides home fast. Don’t hit it, just smooth steady pressure with a bit of rotation. 

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This topic came up a lot, several years ago.  Here is one such thread in which they discuss the O-ring and the dimensions of the machined groove.


Another where someone noticed the placement of the groove and it's proximity to the slot in the housing's clamp.


At one point IE sent out replacement O-rings, iirc.


Please post photos of the mechanical advance mechanism, if you do push the pin out and peek inside.

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