1985 300D leaking oil - PeachParts Mercedes-Benz Forum

Ya Mar · #1 06-18-2010, 05:52 PM

Hello All,

My '85 300D has been leaking oil. It's leaking somewhere from the front lower part of the engine. The bottom of the alternator bracket has oil dripping, and the top and the bottom of the oil pan have lots of oil. So the leak is somewhere in that area. The top of the alternator bracket is free of oil.

It's hard for me to see where it's leaking from because the radiator and belts are in the way. But it looks like it's from somewhere in the front of the engine.

Any ideas of where this leak might be coming from or areas I could check?

Is it common for these cars to leak a bit of oil or should this be a cause for concern?

I used to have an Audi that leaked about a quart of oil between oil changes. The leak didn't really get worse over the years I owned it, I just always carried extra oil with me.

It seems in the last month this car has leaked about a quart of oil, so it's leaking faster than the Audi.

Cr from Texas · #2 06-18-2010, 05:57 PM

How much is on the driveway after overnight? Maybe put down a piece of cardboard so you can visualize better.

Mine is prone to leak, but not enough that I have to add oil between changes.

Ya Mar · #3 06-18-2010, 06:52 PM

I let it sit for about an hour today and there was about a 3" diameter puddle. I'm not sure if it leaks a lot when it's sitting, or if it leaks mostly after it's just been driven.

BoiseBenz · #4 06-18-2010, 10:55 PM

Check that both ends of the oil-drain tube from the separator in the air filter are properly attached--if the filter rubbers are bad this is common. Check the grommet at the tube/pan for the turbo oil return drain; it's the big one. Also check that the turbo center section isn't leaking oil from a seal or either (pressure/small, return/large) line. It could also be the big air "U" from the air filter to the turbo inlet--a loose clamp can let condensed PCV fume oil leak out.

These cars don't need to leak.

Diesel911 · #5 06-18-2010, 11:07 PM

x2 on the Turbo Drain Tube down by where it attaches to the Oil Pan.

Pinpointing where a leak is often easier after everthing has been cleaned and degreased.

layback40 · #6 06-18-2010, 11:55 PM

X2 with 911 on cleaning!! its much easier to find leaks with a clean motor. Its probably the turbo return tube, there are threads about replacing the seal (O ring I think). If its leaking as bad as you say, probably you can clean it & just run it briefly to see any spots that become wet with oil.