Regarding the 1990 300SEL:

The mechanic originally told me there was an engine design defect on this model that results in oil leaks because some internal parts had no seals. He said it was common for him to put on these seals on other customers' cars.

I didn't have any leak, but after having him change the fuel filter and the oil, now I have oil puddles in the depressions where the bolts are to tighten the valve cover. Quite mysterious.

First, has anyone ever heard of that. And second, what is the torque to tighten those bolts in case I find for once there is an easy solution.

Thank you.

How a head gasket that is below the valve cover could pool oil in the bolt wells of a valve cover gasket doesn't make a lot of sense. The gasket inside the oil fill cap if more likely the cause and will set you back a whopping $5.

That motor is pretty notorious for leaking at the timing cover and that will generate a pretty fair amount of oil if left uncorrected. If it is leaking, there would be oil on the passenger side front of the motor down the front of the block and oil pan. It migrates back from there and can go back onto and past the transmission depending on it severity. It is certainly not unheard of for the head gasket to fail and especially if its getting some miles on it, however I would dig a little deeper on this one before you commit to the head gasket.

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6

Thank you for helping me. The car only has 55,000 miles on it and I just went out to check the scene of the crime again. I am not a mechanic but I think I am explaining it correctly.

Viewed from the front, the puddles are in the wells where the larger-head bolts are, to the right towards the air filter. However, I felt it and I see the oil is coming out of the seam where the valve cover is bolted on. On the very top are 4 smaller headed bolts, and they are not too tight - THAT is why I asked about the correct torque specification because that might solve the problem easy. The large-headed bolts down low (at the bottom of the cover) are very tight, the small-headed ones on top are loose. Oil is seeping out of the seam on the right by the air filter and also on the left side.

I do not see any oil leaking or dripping down the front of the engine where you said, and I never see any oil drips in the driveway.

Today is the day to get back to work on this car.
Can anyone please tell me anything about my last post - especially what is the proper torque of those small bolts, and if the timing cover in the front is not leaking, what would be the source of the leak at the seam I referred to in my prior post?

Thank you in advance for any help.

From what you just described it sounds like the oil is leaking from the valve cover gasket. I'm afraid I don't know what the torque specification is, but you should definitely snug up those bolts if they are loose. The valve cover nuts seem to have a tendancy to loosen up over time, at least they did on my 190E. If tightening the loose bolts you described doesn't stop the leak you probably just need a new valve cover gasket, which is an easy and inexpensive fix.

Thank you.
I started to tighten up the bolts because they were all loose.
They never felt like they were getting really tight, not exactly like the threads were stripped but not like they were getting good "purchase" either. Ended up one bolt broke (now I need to get the broken end out of the hole) and none of them felt really tight. Will buy a new gasket and see what happens. Ialways break something while trying to fix something else.

A picture is worth a thousand words... get some pics of that motor and post them up. M103s love to leak oil (and drink it with miles), but since yours is low miles I bet it just seeps here and there due to twenty year old gaskets drying up.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

The valve cover bolt torque is 8.5 Nm, or 6.2 lb/ft. Not very much.
Use a basic criss-cross pattern and bring them down a bit at a time.
I use a 1/4 ratchet, and just snug them down with a small bit of force. They should snug down and give a bottoming-out firm feel. Might check the threads and clean out the holes also.
The valve cover gasket will harden over time, the aftermarket ones seem to last about 2 years. So, go ahead and get a new one.
Very easy job, just snap off the plug wire covers and lay the wires out of the way; then watch for the electrical connectors along the intake side when you lay the valve cover on.

DG

Thanks a million.
I thought that the bolts were too loose when I see that in fact it's the gasket that is no good. Naturally I broke one of the bolts tightening it too much which gives me an extra job. Fix one thing, break something else.

But, I'm on track now and will get this little problem solved.

Thank you again.

Hi there....


I have used valve cover bolts if you need 'em...... I'll send you a couple for free if you cover the measly $3 shipping cost.

Yes, those valve covers like to LEAK! I've been through three gaskets in about a year. Got my last one from the dealership, and I put it on with sealant. The aftermarket rubber seems to get hard very quickly, can't take the heat.

Some folks say I'm crazy for sealing mine down with MB sealant, I say "hey, it don't leak anymore"..... I was losing lots of oil to that stupid gasket, and it was dripping onto my exhaust creating a noxious plume of smoke that would fill the car. Way more annoying that having to clean off my sealant next time I pull the valve cover. You will also find that the oil cap gasket leaks......

Yes, the M103 does have a head gasket issue, but 55K seems a bit early for it by most accounts. Though, the car is almost 20 years old. Still, the head gasket leak is a known issue and you may have to do it eventually. I'd start with all the rubber bits first though.

There are lots of little places for vacuum leaks on this setup, so check all your air hoses carefully when you're in there. Replace as many as you can, especially the vacuum hose that goes to the valve cover.......

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

My first 300SE required a new head gasket at 144K miles. My current one was replaced by the prior owner at 86k.

FYI

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Marc Galassini

'93 300CE 38K Sold
'89 560SL 19K Sold
'91 300SE 191K Totalled 11/6/08
'90 300SE 90K

T.P. your valve cover could be distorted....it happens.
See if you can get a better one at a wreckers.

Thanks to everyone for helping me.
There is a dealer right down the street so I figure to go and get one bolt when the valve cover gasket arrives.

I'm just happy that today it finally passed the emissions test - I was getting afraid I would have to get rid of it because even though I'm not looking for something for nothing, I haven't found a decent mechanic who charges anything close to what I think is reasonable. And I hate it when they start replacing parts by trial and error and running up a big bill, giving me that old story "well, even if you don't notice any improvement it did need that work...."

"T.P. your valve cover could be distorted....it happens.
See if you can get a better one at a wreckers."

It was.... I got a replacement one from a guy in Cali who had already sandblasted it for me. $50. Not a bad deal, considering all I had to do was prep and paint it. Came out looking great. I had got one from a guy on Ebay, and I spent HOURS stripping and prepping it only to find a hole in the casting.......

The problem I was having was more the poor quality of the gaskets I was getting. 4 months use and they would get rock hard - couldn't seal squat regardless of how straight it is.

Finally, I just went overkill on it. MB dealer gasket, MB dealer sealant goop, done and done..... I just got tired of re-visiting that problem over and over. I haven't lost a single drop of oil out of the valve cover since.

Thanks for the tip, though......

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Yeah, you need to be careful when taking your car in for service. Some places are much worse than others. That's the main reason why I try to do my own service whenever possible. That way I don't have to worry about whether or not someone is trying to rip me off. I also save a TON of money and I know the job was done right. (I don't have any formal mechanical training. I've learned everything through working on my vehicles, this web site, and my service manuals.)

The 126 chassis and 103 engine are very well built, and once you get some of these minor issues taken care of I'm sure your vehicle will give MANY miles of reliable service; especially considering it has such low mileage. Don't give up! It's a great car!