Oil leaking from head gasket - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 08-24-2021, 09:28 PM

After cleaning this engine, I noticed that it is leaking oil from the head gasket at the rear of the engine. Before cleaning the engine (strong degreaser at the coin-op car wash), I noticed thick caked up sludge on the side and back of the engine, but thought it was from the cam cover gasket. Everything above the head gasket is very clean now, and no oil leaking from the cam cover gasket. I also have the same problem with the engine in my SLD, so I will be pulling the head and replacing the gasket. I will be sending the head to my machinist to get rebuilt as well.
Has anyone else experienced this problem?

Skid Row Joe · #2 08-24-2021, 10:16 PM

No. None of my diesels have.

.

ROLLGUY · #3 08-24-2021, 11:09 PM

I have only seen this on two of my 617 turbo engines.

BillGrissom · #4 08-25-2021, 02:20 AM

Not on my 1984 and 1985 300D, nor any gasoline car I have with cast-iron block and heads. But, that was an endemic problem in my 1996 Plymouth Voyager w/ 2.4L DOHC engine: cast iron block w/ aluminum head.

It leaked oil to the outside, but compression was fine and no coolant leaks. Mine started around 39K miles, right after the warranty expired, but I ASSumed just a valve-cover leak or from the camshaft sensor nearby so changed those. I lived with it until 90K miles, but the "burning rubber" smell from it dripping on the exhaust manifold became bothersome, esp. after driving up a long hill. I also knew the nature of the problem and fix from others. Chrysler changed to a mulit-layer-steel (MLS) head gasket, which others use today too. I pulled the head off myself and while "in there" did a hand-hone and re-ring and changed rod and main bearings, with engine in car. The ring gaps were still in spec though measurably worn, and the cylinders still had the OE honing marks, making me guess compression should be good for at least 250K miles from new. Unlike engines of the 1960's, better fuel control keeps raw gas off the cylinder walls. Diesel is a decent lubricant so ring and cylinder wear has always been much less in diesel engines. Unfortunately, I doubt we have much choice in head gaskets for the OM617 engine. No oil leaks from the MLS gasket, now at 230K miles.

SonnyMorrow · #5 08-25-2021, 02:49 AM

Rich, I have the same problem on my 1984 300d you saw at Legends of the Autobahn in 2019 albeit coolant is leaking from the head gasket down the side of the block as well as the back. As far as I have seen, it is only an exterior leak and not leaking into the combustion chamber.

I honestly think age could be a culprit at this point and it may start to occur more frequently on our cars, assuming the HG is original. I'm going to pull my head in the near future when time allows.

Luckily I don't drive the car much so a little coolant loss is no biggie. With your head gasket, I assume it is very similar although one of the oil passages is breached.
My W123 was never abused so I genuinely think age could be the case here, how was yours treated in its life?

ROLLGUY · #6 08-25-2021, 09:44 AM

Quote:

Originally Posted by SonnyMorrow

Rich, I have the same problem on my 1984 300d you saw at Legends of the Autobahn in 2019 albeit coolant is leaking from the head gasket down the side of the block as well as the back. As far as I have seen, it is only an exterior leak and not leaking into the combustion chamber.

I honestly think age could be a culprit at this point and it may start to occur more frequently on our cars, assuming the HG is original. I'm going to pull my head in the near future when time allows.

Luckily I don't drive the car much so a little coolant loss is no biggie. With your head gasket, I assume it is very similar although one of the oil passages is breached.
My W123 was never abused so I genuinely think age could be the case here, how was yours treated in its life?

I am not sure about the engine ('85) in my garage on the run stand (it is for sale), but the engine in my SLD has 306,000 miles on it (engine was from a donor with similar miles when installed in the SL). I assume that the engine has not been apart, and that the HG is original. I will be starting a new thread, and posting photos. The engine only has a few miles on it after returning from a drive to the car wash to clean the engine, and there is already much oil flowing down the rear and side of the engine below the HG surface.

C.Doner · #7 08-26-2021, 12:09 AM

Yes, I had the same issue, ended up rebuilding the head. The oil leak was obviously from the cylinder head area, rear right side. It seems you cant walk into the machine shop and get out without doing the go through. After it was all said and done it was timing chain and associated parts, head rebuild, and injection timing device bushings. I think it was good because the head also had significant cracks that had not become leaks yet. I don't think the cracks were associated with the oil leak, but I don't know. They were in the pre-chamber area. That wasn't an issue because there were two more readily available for them to check.

ROLLGUY · #8 08-26-2021, 11:04 AM

I worked for a couple hours last night, and am ready to remove the head and take it to the machinist. Upon removing the right rear most head bolt, it gave a lot of resistance because of being slugged up. You can see in the photo how much sludge is on it compared to the others. You can also see the oil on the side of the otherwise clean engine in the photo. Everything is removed, ready to lift out the head. I will do it later when I get some help.

hercules · #9 08-26-2021, 02:15 PM

Be sure to unshroud the valves while that head is off. Much better performance and better
fuel mileage too. As little as 20 min. job and easy to do.
Also the deeper the valves are cut into head the less performance will be had.

ROLLGUY · #10 08-26-2021, 06:15 PM

I got the head off today with my brothers help. The gasket was definitely compromised in the oil drain area.

vwnate1 · #11 08-26-2021, 07:21 PM

Fascinating .

I've run into this with other vehicles, the methods used to staunch the oil leaks will not be popular here methinks but they do work .

I'm keen to hear about how much if any warpage was discovered on the head .

In 'A' Model Ford and 'B' series BMC (MG, Austin Etc.) engines I learned to paint a 1/2" wide stripe of flat white latex house paint on both sides of the head gasket .

Another old timey fix is to strip some copper wires and lay them around the edge of the block's deck before laying down the head gasket .

As I said : this is for older, low compression engines .

hercules · #12 08-27-2021, 04:10 AM

Mercedes made a upgrade to the head gasket years ago. Why? because it almost always
leaked. No warpage was usually found.
If there is caked dirt at the rear of the head only two places to leak valve cover gasket
or head gasket.

ROLLGUY · #13 08-31-2021, 01:49 AM

I got the head back from the machinist today. You can clearly see on the block deck the spot where the oil was leaking (third photo). I always use WD-40 and a sharpening stone to clean up the deck before installing the gasket and head.

Bengoshi2000 · #14 09-01-2021, 09:11 AM

That valve cover... it's glorious!

Quote:

Originally Posted by ROLLGUY

I worked for a couple hours last night, and am ready to remove the head and take it to the machinist. Upon removing the right rear most head bolt, it gave a lot of resistance because of being slugged up. You can see in the photo how much sludge is on it compared to the others. You can also see the oil on the side of the otherwise clean engine in the photo. Everything is removed, ready to lift out the head. I will do it later when I get some help.

dieselbenz1 · #15 09-01-2021, 09:28 AM

Was the head shaved with the valves still in?