OhioS55

As you can guess from my forum name, I have a (2003) S55, but also a 1997 E320, engine 104.995, inline 6, which is the subject here. The car wasn't leaking anything when I got it last year, with 100,000 miles on it.

When it was time for an oil change I took it to local indy shop that specializes in imports, which has been around for quite some time. When I picked the car up I found that they had put in some "synthetic blend" oil, not Mobil 1 etc. I figured they ought to know what was ok and not, so I didn't think much of it at the time. Some weeks later, oil spots started to appear on the garage floor. Another shop just up the street, that does not specialize in anything particular, looked at it and said the head gasket is leaking, at the back end of the engine.

I have recently found references to leaks being caused by the introduction of non-synthetic oil into old engines. Whether this happens or not is probably irrelevant now, since the thing has already started leaking. I included the story for background.

I have done some reading on the head gasket replacement, and have the star DVD for W210. It's a big job of course, but I could do it. However, I am thinking of trying a couple of things first.

A Buy a set of new head bolts, take out and replace the old ones one at a time, and re-torque according to the instructions on the start service CD. This includes a 3-step process in an exact order for the 14 bolts - torque to spec through the 1-14 pattern, then 90 degrees more, two times, in the 1-14 pattern.

B Replace the oil filter, drain "synthetic blend" out, replace with Mobil 1, see if oil leak stops.

Are either of these worth trying, or do I need to get ready to do the whole head gasket job?

I won't be going back to the "import specialist" shop - I didn't know better at the time, but they should have.

desired_speeds

Its not uncommon for the inline 6s to leak on mercedes. I think your best bet would be to just do the head gasket. I can see no reason why oil would cause it to leak.

illest

Sounds suspicious. Get the right oil in the car first, then clean the engine and monitor the leak to see how bad it is.

ohlord

The issue with leaking oil seals is not a head gasket it would be a timing cover or valve cover gasket. The problem is caused on older engines when switched to synthetic oil not the other way. Your M104 was designed for conventional oil not mobil 1 synthetic. Change the oil to an API spec oil 10w40 wt conventional.
Torque your valve cover gasket or change it. And drive the car.
A blown HG would have far more issues than a simple oil leak.
The import shop using the blend was at least half right,you thinking the engine needs mobil 1 synthetic like the later M112 and M113's is all wrong.
So don't condemn the shop completely,if the engine had been run with conventional oil as designed from the beginning it most likely would still be leak free.

OhioS55

I am REALLY glad I asked before tearing the engine apart. I didn't question the head gasket diagnosis from shop #2. It seems obvious now. The valve cover job should be much easier.

OhioS55

So I got the valve cover gasket, and 12 rubber washer-like things. Before tearing into the job, I did a little looking around the edge of the valve cover, with flashlight and mirror - no leaks visible. Put the front wheels on ramps, got under to look around. Left side of the crankcase is surprisingly clean and dry for 107,000 mi motor. Right side is another story. I can understand somewhat why the local non-mb-specialist shop concluded that I need a new head gasket. The right rear corner of the cylinder head where it contacts the crankcase, is where the oil seems to originate, enough to drip on the floor a little. I attempted a cell phone photo but it's not great.

I believe the gold colored round gizmo in the photo is a crankcase sealing cap of some sort. The visible bare aluminum to the upper left of this is the lower rear-right corner of the cylinder head. Attached to the visible aluminum is an exhaust pipe or manifold flange. I'm as far from an expert as it gets, but it appears that everything above the head-crankcase contact line is perfectly dry, while the right side of the crankcase is wet with oil.

At the front right corner of the head, at the head-crankcase contact area, there seems to be another leak, although it's likely that the timing cover is the problem here. This leak is much less severe than the one at the back of the engine.

The engine starts well, runs very smooth, lots of power. No visible blue smoke. Maybe this leak is no big deal, and if it's not going to get worse, I can keep cardboard under the car and check the oil level as usual. It would be better if the car didn't leak anything, I think.

It doesn't seem that replacing the valve cover gasket would fix this problem. I understand that the head gasket is a compression seal, which makes sense - I took apart a couple of lawn mower motors many years ago, and if you take off the head, the piston is right there. I have heard of valve stem leaks, which I think leak the oil into the cylinders causing tailpipe smoke rather than oil on the outside of the engine. What else could be going on at the rear corner of the head?

Hirnbeiss

The most common leak on the M104 is the Stirndeckel (forehead cover) or timing cover, at the top passenger side junction. In many cases, oil blows back making it look like a leak comes from elsewhere.
Take your time in isolating the location, since an oil leak is hardly super-urgent. You should do a good cleaning and then check again.

OhioS55

Yep, there is a leak at the timing cover, right where you said. I would have never thought of the oil migrating from there to the back of the engine. The car has done almost all highway for the last 7K, so this would make sense. I will clean that side of the engine and find out.

I was concerned that this could be the start of a larger problem, but I see that no one thinks so, so I am less worried about it now. It's just an inconvenience, and maybe I'll get it fixed in time.

ohlord

Post #4 from 2 weeks ago. Change to the proper oil.tighten timing cover and
Valve cover and drive

01BlackE320

First off, never go back to that Indy shop. They're scammers.
Do as Ohlord prescribed if you want at you leasure or clean the engine and try to get a better idea exactly where the leak is coming from. The heavier grade non-synthetic will probably leak less.
Your problem is very minor for a 15 yr old car. Most would ignore.