OM603 oil leak & headgasket - PeachParts Mercedes-Benz Forum

JHZR2 · #1 10-15-2018, 10:12 AM

1991 350SD

Last night I did the oil drain plug fix (new threaded insert), and cleaned the oil pan.

Ive driven 13 miles of non-challenging, moderate highway speed (55-60mph) operations.

I looked under this am (pardon the pics, it’s raining), to see this:

From only 16 miles!

I know there is some oil coming from that side. Thought it may have been the intake, especially that seal for cylinder #1.

It’s not the VC gasket.

Different view - hard to get focus.

There is oil in the head bolt, fwiw.

I can confirm that a very slight amount of oil does seep into the coolant. Such a small amount that it can be absorbed from the plastic bottle with a paper towel, to get to clean coolant. But it is there and it is engine oil.

I bought this car knowing the risks, and from a body standpoint, it is very clean, absolutely no rust, and runs very well.

So this may just be the start of a leaky turbo, there likely is a HG issue.

But wanted to get folks’ thoughts on this.

As I mentioned when I bought it, I priced in an engine repair. I’m thinking a preemptive HG replacement is prudent.

Opinions??

Maxbumpo · #2 10-15-2018, 10:32 AM

I've had an oil leak like that from the injection pump. There is a big plate on the bottom of the IP that has a seal that dries out and leaks, as well as the side plate. There is also the seal between IP and the block, which is prone to leaking if it is old and dry and someone tries to adjust the IP timing.

Oil in the coolant is definitely a bad sign. I'd say clean off the oil from the head bolt and the engine in general, and try to narrow down the source. Pulling the head is not a small thing, if the risk is low and you can put it off until the time and place of your choosing, that would be preferable.

Diseasel300 · #3 10-15-2018, 10:35 AM

On that side of the engine and in that location, you pretty well only have the IP. Mine leaks down the side of the block and also pools on the engine mount arm. It's on the agenda to reseal it this fall/winter. Ironically, it's the only oil leak on my engine (other than the turbo slobbering oil, but that's technically internal).

JHZR2 · #4 10-15-2018, 11:32 AM

Quote:

Originally Posted by Maxbumpo

I've had an oil leak like that from the injection pump. There is a big plate on the bottom of the IP that has a seal that dries out and leaks, as well as the side plate. There is also the seal between IP and the block, which is prone to leaking if it is old and dry and someone tries to adjust the IP timing.

Oil in the coolant is definitely a bad sign. I'd say clean off the oil from the head bolt and the engine in general, and try to narrow down the source. Pulling the head is not a small thing, if the risk is low and you can put it off until the time and place of your choosing, that would be preferable.

HG I can and will do on my schedule. These are hobby cars and I have other DDs. But I can get it done (at a Bosch/machine shop that I trust) soon and have the car driveable (it starts, idles, and runs beautifully, but I’d like to remove any concerns before losing thousands of highway miles on it). Since it’s a rod bender I do want to be careful before it’s too late!

That said, I’m far less concerned with an IP overboard leak. I did pull an oil sample to look for coolant and fuel in the oil.

I do see some wetness beneath what I believe to be the lift pump. Tried to get some other photos. The mount arm is oily but not wet. That’s a finger swipe in the oily grime on that from over 1000 miles ago.

I’d anticipate that the IP leaks would be attributed to the oil by the level sensor and further aft. What i don’t get is the forward leak that comes down directly on top of the drain plug.

Above that, other than cyl 1 intake, it seems pretty dry. Certainly the side of the block, by the painted “1” it is wet, but other stuff isn’t oily.

JHZR2 · #5 10-16-2018, 12:11 PM

Car is running beautifully. Oil loss is real but seems to only be to the exterior. I plan to pull the intake but think I’ll have th Bosch shop premptively do the HG and seal the IP. Are there improved seals for the IP?

Proctor750 · #6 09-28-2022, 09:10 PM

How did oil get onto that cyl 1 bolt?

JHZR2 · #7 09-28-2022, 11:42 PM

Quote:

Originally Posted by Proctor750

How did oil get onto that cyl 1 bolt?

Into it? No idea. Though keep in mind this engine had oil crossing over into coolant.

I don’t know that the HG offered any clues.

Murkybenz · #8 09-29-2022, 01:10 PM

Cylinder one is normally the one where the head gasket goes and eventually causes clouds of grey smoke as the oil gets into that cylinder and it also can knock quite hard , presume yours has just escaped via a different route.

Proctor750 · #9 09-29-2022, 02:02 PM

Wow my 350 is also impala (desert) metallic brown.
I'm tracking a similar oil leak which appears to originate on or near that same cyl 1 bolt... no oil in my coolant though and no smoke. Runs like a top.