M115 rear main seal leak. - Mercedes-Benz Forum

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post #1 of 5 (permalink) Old 01-24-2011, 01:49 PM Thread Starter
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M115 rear main seal leak.

I posted the below message in the general forum but did not get any replies and figured I'd repost here........

"Like the title says...my W123 with a 2.3L M115 seems to have developed a leak from the rear main seal.

I first realized I had a problem when I saw a pool of oil, maybe 4inches across, where I usually park my car...! Checking the oil it was slightly above the low mark... topped it off and kept an eye on the oil-pressure gauge.

Based on the amount of oil on the ground I expected it to get low fast but surprisingly the level dropped quite slowly.. After some messing about I figured that a lot of the oil was pooling in the bell-housing (held there by the forward motion of the car ?) and when I stopped the car puked it out. Strange thing is when I park the car with the engine running it only drips out and the main part of the leak only starts when I shut off. This engine has some high mileage and maybe blowby/crankcase pressure keeps the engine away from the drain hole?

Anyway....the whole car is not really worth the cost of a re-build so I was wondering if removing the upper-sump and just doing the lower half of the seal is worth the effort. I read in a previous post that the drag link has to come off but are there any other problems..? I also thought of unbolting the engine mounts and jacking the engine up a bit,maybe get a few more inches of clearance. Thoughts on this?"

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post #2 of 5 (permalink) Old 01-24-2011, 08:41 PM
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If it were me, I would drop the transmission and do a complete RMS job.

1975 240D - boot scoot 'n boggy'n.
1995 Geo Metro 1L 5 speed - Fuel sippah.
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post #3 of 5 (permalink) Old 01-24-2011, 09:39 PM
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I'm pretty sure it's a rope seal in which case the crankshaft has to come out. If you're lucky and it's a newer style seal that can be inserted from the back of the engine, then go ahead and replace it. Check with the parts dept or the Classic Center.

Near Manassas Va. '65 220S, 2006 Ford Crown Victoria Police Interceptor, '99 Volvo V70, '72 350SL 4 speed

Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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post #4 of 5 (permalink) Old 01-25-2011, 02:27 AM
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It is a rope seal, so replacing the lower half might help. You can remove the oil pan by loosening the engine mounts and lifting it. It is described in the FSM:

01 Crankcase and Cylinder Head - M115
select 01-310

Sometimes other types of oil will help reducing oil leaks.
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post #5 of 5 (permalink) Old 01-25-2011, 01:42 PM Thread Starter
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thanks for the link....

I'll probably drop the pan. Probably a load of gunk in there.....

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