oil leak 85 300 SD - PeachParts Mercedes-Benz Forum

yuke · #1 09-22-2014, 08:45 AM

I have a pretty bad oil leak not sure where it is coming from? It looks like I have a slight crack in the housing on rear of motor where it connects to trans. The leak might be from the rear main. Seems I leaked a qt. in about 3,000 miles. I will try to post a picture. All thoughts are welcome.

mattwestm · #2 09-22-2014, 10:35 AM

I've got a similar issue going on with my 84 300SD. I usually get a few drops on the ground overnight after driving around town. When driving for longer periods, I get about 10 little drips. It's very difficult to tell where the leak is coming from due to the crud. I am getting ready to degrease. I would advise doing this first. Then you will be able to locate the leak source.

It could also be a leaking valve cover gasket (which leaks down the back) or a leaking oil filter housing gasket (not the cover, but the gasket between the engine and housing).

Does anyone have any good ways of degreasing? Will a car wash sprayer work?

SD Blue · #3 09-22-2014, 10:52 AM

My guess is a valve cover gasket. There is another thread here that talks about different techniques to get it to seal properly. From what I've read, and experienced, the best method is to re-torque the valve cover bolts after the engine has warmed.

I've found that a car wash sprayer works well. However, if the oil residue has dried to the consistancy of tar then it really pays to pretreat. Be careful what you use to pretreat as many of the stronger degreasers can oxidize the aluminum. Usually, dishwashing soap works well, applied full-strength to pretreat problem areas.

Junkman · #4 09-22-2014, 11:46 AM

If on the driver's side, valve cover or oil filter housing gasket or banjo on the oil line from the oil filter housing to the turbo (requires 2 copper washers 15mm I think).

On the passenger side, valve cover. Anything else except the turbo drain and you may as well pull the parts down to the block and do it all. Elring has a gasket set that seems to be working.

vstech · #5 09-22-2014, 01:11 PM

looking at your picture, the oil is all over the lower pan and everything rear of it.

this could be front main seal, valve cover, head gasket, turbo oil return, air cleaner oil return, or even Injection pump seal...

I agree, clean the motor from top to bottom first, then follow the trail forward...

leathermang · #6 09-22-2014, 04:23 PM

Quote:

Originally Posted by yuke

;;;;; rear of motor where it connects to trans. The leak might be from the rear main. ....... All thoughts are welcome.

At the rear of the engine.... is the ' end ' of the oil passage which feeds the oil squirters .... it is ' closed ' by a pressed in large ball bearing... why it did not have a ' normal' closure like a bolt I do not know... but if that leaks then it will put out oil at a place which might look like it was coming from the rear main seal... looking at the engine from the rear.... I think it is about the 8 oclock position...

yuke · #7 09-22-2014, 04:51 PM

There seems to be a hairline crack in the houseing where ost of the oil seems to coming from I am watching it closely and will try to figure how to seal that crack if indeed tnat is where it is coming from. MY second guess is it is the rear main engine has to come out to repair that I guess.

leathermang · #8 09-22-2014, 04:56 PM

Hairline crack in exactly what housing ?

yuke · #9 09-23-2014, 08:27 AM

Quote:

Originally Posted by leathermang

Hairline crack in exactly what housing ?

Right behind the oil pan bottom of engine where it meets the trans. If I wipe the crack clean I can see a slight oil seepage immediately. I will look closer today again. Is there a picture somewhere of that tube that is closed with a ball bearing ? I will keep looking just hope its not the rear main.

leathermang · #10 09-23-2014, 09:19 AM

The FSM has that picture...

yuke · #11 09-23-2014, 04:05 PM

Quote:

Originally Posted by leathermang

Hairline crack in exactly what housing ?

The housing leathermang is pot metal on the bottom of the engine right where it bolts to the trans. it has an oval hole cast into it that is about 2" x 3" in diam. the hairline crack is in this casing where I think most of my leak is coming from. It will leak a spot about 3" x 6" when sitting about 5 hrs. after running which will make a mess whereever its parked in short time. As far as to fix this hairline crack to make leakproof I am not sure how I will approach that yet. I will try to attach more pictures one is with a ruler pointing to the spot where the crack is in the caseing other picture shows what it leaked after being run at operating temp.

leathermang · #12 09-23-2014, 04:22 PM

If it is part of the engine it should be cast iron...
why do you think it is pot metal ?

SD Blue · #13 09-23-2014, 05:31 PM

See if you can give us a photo right side up. It's difficult to see what you are talking about when they are upside down or sideways. I'm still not sure of the area you are talking about. Many times the leak is further forward, such as the oil cooler lines.

Are you sure the seepage is coming from an oil area of the engine or is it just pooling there?

vstech · #14 09-24-2014, 07:37 AM

Oil seeps from everywhere when it is accumulated from a leak... You need to wash the engine of all the accumulated liquid. A car wash will help.

yuke · #15 09-24-2014, 12:38 PM

Quote:

Originally Posted by leathermang

If it is part of the engine it should be cast iron...
why do you think it is pot metal ?

Because a magnate will not stick to it leathermang I am pretty sure all that oil is coming from that crack have to figure how I will try to patch it. In the meantime I have to pull the driveshaft off as I have a very bad vibration problem think it is center bearing holder or u joint will get started on that shortly.