W123 300d Oil Leak...... - PeachParts Mercedes-Benz Forum

Shawnb · #1 02-17-2017, 03:57 PM

I have a 78 300D.

I've had it a few months, and have put about 5k+ miles on it so far. When I first purchased it, no oil would touch the ground and the pan and trans were clean of oil...

Bottom of my pan, and trans are coated in oil now and I cannot find where it's leaking from.... Really hoping it's not the rear main seal, as that would be a major nightmare to tackle at my house. Would the rear main cause that much of an oil leak?

Any ideas?

Junkman · #2 02-17-2017, 05:07 PM

Don't know about rear main. You can eliminate everything else.

http://www.peachparts.com/shopforum/diesel-discussion/328295-leak-free-617-a.html

&/or you can clean it off and watch for the leak or put dye in and check with a light.

Diseasel300 · #3 02-17-2017, 09:33 PM

What color is the oil? Is there oil coming from higher up on the block? Valve cover gasket perhaps? Make sure the breather tube in the valve cover is clear and passing vapor to the air cleaner, if it is clogged up for some reason, the blowby gasses can force oil out of many areas on the engine.

sixto · #4 02-17-2017, 09:45 PM

A rear seal leak wouldn't work its way forward. Check the oil cooler hoses. If they're leaking, don't put off repair.

Sixto
83 300SD
98 E320 wagon

Ceristimo · #5 02-18-2017, 01:29 AM

Man, these older diesels have a reputation of seeping oil. I'm not saying it's normal, but it kinda seems to come with the territory of driving these old cars. It kinda sounds to me that whoever sold you the car might have degreased everything prior to selling and you're seeing now what most old diesel owners are seeing: an engine block that's oily, with oil splattered on front suspension parts, pan and transmission. Mine is the same.

Again, not saying it's normal, but as long as it's not your rear seal...Betsie pisses oil wherever she goes. At work I park in the back, and at home I have cardboard in the garage. I stopped worrying about it a long time ago. Rule out the important things (main seal, oil cooler hoses) and then go from there.

Shawnb · #6 02-18-2017, 08:16 AM

Quote:

Originally Posted by Diseasel300

What color is the oil? Is there oil coming from higher up on the block? Valve cover gasket perhaps? Make sure the breather tube in the valve cover is clear and passing vapor to the air cleaner, if it is clogged up for some reason, the blowby gasses can force oil out of many areas on the engine.

It's clear, and attached properly. It was blowing off for the longest time, till I redid it.

Engine runs and sounds great, prior to the leaking I would never notice any oil consumption on the dipstick. There is a fair amount of blow by though. When the brother tube was popping off, it would look like the car was overheating at long stops.....

Diseasel300 · #7 02-18-2017, 09:27 AM

If it's blowing the tube off and has that much blowby, I think you've found your problem! With that much blowby, it'll force oil out of anywhere it can on the engine, especially at higher revs.

Shawnb · #8 02-18-2017, 10:44 AM

Quote:

Originally Posted by Diseasel300

If it's blowing the tube off and has that much blowby, I think you've found your problem! With that much blowby, it'll force oil out of anywhere it can on the engine, especially at higher revs.

It wasn't clamped securely before. It hasn't blown off since I've redone the line. Maybe I should just vent it, and deal with the smoke at idle.

Diseasel300 · #9 02-18-2017, 11:15 PM

That's not the point. If it has enough pressure to blow it off, that's a bit much. Certainly enough to make your gaskets and seals weep at cruising speed.

Diesel911 · #10 02-18-2017, 11:43 PM

As indicated in post #5 about degreasing. Once degreased the source of leaks becomes a lot easier to find.

When I bought mine I had Oil and layered dirt from the Engine back to the tail of the transmission. After 3 cans of Engine degreaser I found that it was the valve cover gasket causing the bulk of the Oil leak and that was 2007. The rest of the leaks I lived with till the Turbo Drain grommet went bad.

Shawnb · #11 02-19-2017, 09:17 AM

Quote:

Originally Posted by Diseasel300

That's not the point. If it has enough pressure to blow it off, that's a bit much. Certainly enough to make your gaskets and seals weep at cruising speed.

Looks like I will be leaving it disconnected.

MongooseGA · #12 02-19-2017, 11:23 AM

I have a few leaks in my W123 as well. So far I've determined they're coming from the VC gasket, oil pan gasket, oil filter gasket (o-ring that seals the hard line at the bottom of the housing) and I think that's all. I just need to allot the time during one of my next oil changes to tear it all apart and replace. I do get oil blowing out of the top of my valve cover as well. Is this what you guys are referring to as blow by? There's also a thin layer of oil in the air cleaner housing.

Shawnb · #13 02-19-2017, 11:37 AM

Quote:

Originally Posted by MongooseGA

I have a few leaks in my W123 as well. So far I've determined they're coming from the VC gasket, oil pan gasket, oil filter gasket (o-ring that seals the hard line at the bottom of the housing) and I think that's all. I just need to allot the time during one of my next oil changes to tear it all apart and replace. I do get oil blowing out of the top of my valve cover as well. Is this what you guys are referring to as blow by? There's also a thin layer of oil in the air cleaner housing.

Yep.

Mine was leaking at the top of the valve cover, and blowing off the connection under the air cleaner. I fixed that a month or so ago, and it hasn't blown off. I have been noticing oil leaks though..

Just disconnected it this morning, and plugged the hole at the intake manifold. Hoping that will cure the new oil leaks I started having.

I left it disconnected and had it running for 5 minutes, and didn't notice any smoke? It used to smoke like crazy, that's how I knew it wasn't connected anymore.

The only change has been using synthetic 5w-40 to just putting in Dino 15w-40. I doubt that matters.

Shawnb · #14 02-19-2017, 03:11 PM

I just did the valve cover gasket, the back is leaking. Could it be causing that much of an oil leak? The whole bottom of the motor and trans are wet with oil. This is something that has recently happened.

Is there a way to get the valve cover gasket to seal better?

ROLLGUY · #15 02-19-2017, 04:27 PM

Quote:

Originally Posted by Shawnb

Is there a way to get the valve cover gasket to seal better?

I have seen it where the wire to the sensor on the intake manifold gets caught under the gasket, but yours does not have this wire. I usually clean the cover and head real good, and use Gaskacinch (basically rubber cement) on the cover, and the bottom of the gasket before installing the cover on the head. I have yet to have one leak a drop. The key is to be sure every surface is clean. It is best to do this job when the engine is cold, and most of the oil has drained off the side of the cover. If oil is allowed to get in the gasket before the cover is tightened, it has a good chance of leaking.