OM 603 Oil Leak - PeachParts Mercedes-Benz Forum

tomkanis · #1 05-02-2003, 10:10 PM

Finally got time to clean my engine yesterday. I found a small oil leak coming out of a head-bolt hole near #2 Cylinder. It's apparently been doing that for some time. Has anyone here seen a similar problem?

Tom Kanis
87 300 SDL

sixto · #2 05-03-2003, 04:15 AM

Are you sure it's not dripping from the joint between the crossover pipe and the intake manifold?

Sixto
91 300SE
87 300SDL
83 300SD

tomkanis · #3 05-04-2003, 07:27 PM

No, it's coming out around the bolt hole. I sure hope this isn't what I think it is (a head gasket), 'cause I lost my job last week.

Tom Kanis

mercedesmatt · #4 05-05-2003, 10:35 AM

mine done the same thing, the head bolt hole is also a drilling for a oil passage. it is considered normal. but if you want to stop it all you have to do is remove the bolt. clean the threads and the hole with brake kleen, dry with compressed air. and put a small amount of blue silicoln on the threads of the bolt and reinstall. thats what i done to mine and it worked wonderfully!! pretty easy job, be sure to retorque the headbolt to factory specs!!!

gsxr · #5 05-05-2003, 03:32 PM

I'm almost positive the head bolt does NOT go into an oil passage. I had the head off '87 last year (replacement) and IIRC, all the bolt holes were blind - did not enter any coolant or oil passages. The leak you mention is almost guaranteed to be from the #2 intake runner where it meets the head, this is a VERY common leak, and is right near the head bolt. The other (less likely) cause is the head gasket leaking oil that is appearing out the bolt head, but I really doubt that. I sure wouldn't pull the head off for this!

BTW - you don't have very high pressure in the cooling system when the engine is cold... do you?

Good luck,

tomkanis · #6 05-05-2003, 08:32 PM

No, but there is some residual pressure when you pop the lid. If you are going where I think you're going; there is no water in the oil.

I took it on a 270 mile run after I cleaned it, and the leak was visible. The side of the block was very durty with old oil accumulation. My indy has had it in his shop, and has never pointed out the problem to me, but it has been going on some time apparently.

Tom Kanis

gsxr · #7 05-05-2003, 08:55 PM

Slight residual pressure is OK. Try to squeeze the upper radiator hose when it's cold. If you can pinch the two sides together, you're probably fine. If it's so tight you can't squeeze it, start saving your pennies for a head replacement. Coolant in the oil is pretty rare, even with a nasty crack. The typical failure mode puts combustion pressure in the cooling system, and eventually will hydrolock the engine when it gets bad enough. If/when the gasket goes, oil in the coolant is a lot more common than coolant in the oil - so you can't take clean (black) oil as a sign that all is well. Just a friendly warning from someone who's BT, DT.

Have you pressure washed that specific area yet? I still would bet a cold frosty beer of your choosing that the source of the oil is the intake charge pipe, not a head bolt...

CSchmidt · #8 05-05-2003, 08:56 PM

gsxr,

My '87 has just started a leak around cylinder #1 where the intake goes to the head (yup you are right, pretty common). Not very much, I still don't use 1/2 quart in 3000 miles (@240K miles). Is this just blow by accumulating in the intake and finding a place to leak out?

Chuck

gsxr · #9 05-05-2003, 09:10 PM

Chuck, yes, you are correct. It is blowby from the PCV system, going back into the air intake elbow, and blown through the charge pipe. It is a tiny amount and won't show up as oil consumption, but can look ugly as it weeps out the gasket. It helps a little if you disconnect & plug the EGR and the turbo ARV. A new gasket with a thin coat of Hylomar sealant should cure the leak, after careful cleaning of the sealing surfaces.

sixto · #10 05-05-2003, 09:16 PM

Might it instead or also be a leaking turbo bearing seal?

Sixto
91 300SE
87 300SDL
83 300SD

gsxr · #11 05-05-2003, 10:16 PM

Yes, but according to assorted MB service documentation & TSB's, oil in the intake manifold is normal and not a cause for warranty repair (which to me means OOW repair too). If you have zero blue smoke and oil consumption is relatively low, it's usually not an issue.

If it really bothers you and need to find out, you can route the PCV pipe to a plastic containter or small K&N fitler something, and plug the intake hole. Remove & clean the charge pipe completely. Drive the car for a few hundred miles, then pull the pipe & look inside. If there's oil, it has to be from the turbo. If not, it was from the PCV inlet.

Marcb · #12 12-31-2003, 03:55 PM

I've recently noticed a small "weep" of oil in the front of the engine on my 87 300D. I'm hoping it isn't leaking from the headgasket because I have no residual pressure in the cooling system when the car is cold and it doesn't overheat. Any thoughts?

sixto · #13 12-31-2003, 04:09 PM

If it's coming from the vacuum pump, replace the pump ASAP if not yesterday. It might be coming from the big center bolt of the belt tensioner. You should be able to check that it's tight without removing the fan. It takes a 12mm hex tip.

Sixto
95 S420
87 300SDL
83 300SD

gsxr · #14 12-31-2003, 04:45 PM

If it's coming from down low, it might be the front crank seal. Best thing to do is thoroughly wash the front of the engine so ALL oil is gone, drive the car for a bit, and locate the true source. The vac pump or tensioner are DIY jobs, the front crank seal is not (IMO).

Marcb · #15 12-31-2003, 05:31 PM

Hmmm, I'll have to check the big bolt of the tensioner. I have replaced the vacuum pump and it was the original one on the car when I bought it. It now has a new Pierburg and all seems well in the vac pump area.