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View Poll Results: Which method for valve seal replacement do you prefer for the OM602/603?
Bring each piston to TDC as you do its valve seals. 2 50.00%
Use air pressure to hold the valves up. 1 25.00%
Do both. 0 0%
Ignore the smoking problem and add oil occasionally. 1 25.00%
Voters: 4. You may not vote on this poll

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Old 10-11-2009, 01:02 AM
Jeremy5848's Avatar
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Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,393
OM602/603 valve guide seal replacement technique

This is a "technique" question. My '87 300D Turbo (W124, OM603) has an occasional (oil) smoking problem, especially after extended idling. My suspicion is that the replacement head (PO overheated the engine and cracked the original head) was rebuilt with aftermarket valve guide seals that don't seal as well as OE seals.

Although paying a mechanic to replace the seals is rather expensive, the job is within my skill level provided my support group (meaning YOU) is with me. It can be done with the head on the engine and if I can make a valve spring compressor by modifying a home-made VW tool design, I can do the job inexpensively. If it doesn't fix the smoking problem I'm not out very much so long as I don't break the camshaft.

For this procedure, one can either use air pressure via an adapter through the injector or glow plug holes to hold the valves in place or one can rotate the engine so that each piston is at TDC when its valve keepers are removed.

My indy does not trust the air pressure method and recommends turning the engine. He feels that having each piston at TDC is a better way of insuring that the valve cannot fall.

OTOH, the mechanics at the local dealer prefer the air pressure method. They note that even at TDC the valve will slip down a little bit, making it harder to get the keepers back on. An additional advantage of the air pressure method is that there is less risk of screwing up the valve timing by losing track of how many times you've rotated the engine.

A "belt and suspenders" person would say "do both." A fourth option is to continue adding oil every month or two and ignore the problem.

What says the forum? I'd appreciate hearing from people who have done this job.


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Old 10-11-2009, 01:05 AM
kmaysob's Avatar
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Location: mesa az
Posts: 1,673
id use the air pressure method first. i suppose you could do both to limit the drop if it does. without air it WILL drop a little and you will have to find a way to push it up into place.
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Old 10-11-2009, 06:47 AM
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Join Date: Oct 2006
Location: Beachwood, NJ
Posts: 462
I have used rope for the same job on a chevy. Feed rope into cylinder and bring piston up to hold valves. The pre-chamber would have to be removed for access, may not be worth the effort unless you lack a air supply.

Last edited by NJ300sdl; 10-12-2009 at 08:18 AM.
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