Aftering driving at highway speeds for 1 1/2 hours, there is a trail of oil from the oil cap all the way to the back of the valve cover. Obviously the trail is from the wind, but is it ok for oil to be leaking past the oil cap? BTW the oil cap seal has been replaced. My oil pressure is great, hitting 3 bar at 1200 rpm. My fuel economy on the last tank was 31 mpg. So it appears the engine is in good shape. I am just concerned that this oil leak is a sign of excessive blowby. When I pull off the air cleaner assy., there is a little oil sitting on the lip to the turbo housing.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Greetings Rick,

I wish I was getting your fuel mileage, but then again I don't have a turbo which may account for the extra 3 mpg. I think like all of us that have been thrown into a Summer like setting, our oil gets and stays hotter sooner, and ultimately thins out quicker and stays that way for the duration of our trips. Rick, if you really want to see your blowby in action remove your oil cap with the engine running, it should puff pretty heavy in your face if you have any at all. Now accelerate the engine somewhat and watch the puffs go away slowly as the engine actually develops more ring to wall sealing. I think it's just the nature of this beast we all live with. I'm not about to do any major teardown because I only have 300 psi per cylinder compression. As the manual reads, that's quite normal wear and acceptable. If the slight dribble of oil on the valve cover is irratating to clean off get the whole rubber type of gasket instead of the composite and your cap leak will dissappear.


Charles

Well I don't mind cleaning up the valve cover, I was just wondering if this was something to be concerned about. I guess this falls under the old saying..."if it didn't leak oil, it wouldn't be a diesel".

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Greetings Rick,

I'm learning just like you that these Benz's are temp sensitive. With Winter, even the valve cover only get's warm after a fifty mile drive, and the IP stays basically cool. The opposite happens during the Summer. After only fifty miles of driving the valve cover is quite warm if not hot to the touch and the IP now is quite warm as well. I'd like to think that oil stays the same viscosity whether it's hot or cold, but the fact remains that it actually remains cooler in the Winter and presses the outer limit during Summer heat. I have found that using a rubber gasket on the oil fill cap just about rids any leakage year aound. As far as leaks go, I really guess I'm lucky that I don't have any real leaks to speak of, from tranny to oil pan to fuel system except when I back down the steep grade driveway I have, I get rear oil pan seal leakage. I'd like to change it out because I know it must seep as well just going down the road but on level ground it doesn't leak a drop. Just haven't justified the time to spend on the seal replacement until it becomes a real concern of level leakage.

Thanks,

charles

Hello Rick, and Hello Charles, my two best Mercedes buddies, are here talking to each other. That is so lovely.

Rick, I think that if your oil cap is leaking at all, you should either replace it, or get another new seal. My other idea is, is it possible it is coming from the breather directly behind the oil filler cap? My breather leaves an oil mess no matter how many times a day I wipe it clean.

I say this because that elbow and hose are made of such unelastic plastic that it is very likely that they are both loose. Especially if they are original. I eventually put a hose clamp on mine, because it was leaking. I would like to someday replace it with a nice tight new elbow and hose.

Does that make any sense?

Patsy

Greetings Patsy,

Long time no hear from you, or have I not been posting to the right folks? I wish I always had simple problems like oil cap leaks or seeps. I am in a major way looking for a way to install an A/C system complete, or almost complete on this black beast of mine, and haven't found anyone who answers their phone during the week. Hopefully this next week will be better.

Keep the black smoke puffing and the wheels a rolling

Charles

Hi Charles, Oh heck, I have the same problem. I have to redo my A.C. system with a new compressor, and the works. I am staying with the old freon. My problem is that I'd like to do the work myself, but I want someone else to evacuate the system, store my very expensive freon for me, and then refill it when I'm done. Am I being ridiculous?

Patsy

Hey Patsy, The oil seeps from both the oil cap and the breather elbow. The new gasket I got, which was OEM, appeared to be rubber. I don't know if this has anything to do with it, but my oil cap is not original. It is one of the later, black plastic ones. I really would like to get a hold of an original metal one with the "Star" on it.
So you want to talk about A/C. Well I know mine doesn't work right now. I replaced the belt, pushed the switch and nothing, except the blower fan speed got a little faster. The A/C compressor clutch does not engage. Someone once told me that if the freon is low, the A/C system won't let the clutch come on. Is there any truth to this?
Here in NJ we just went through 2 weeks of mid 70s-mid 80s temps. I drove around with the sunroof open. Now, for the last couple of days and the rest of this week, it's in the 60's and raining.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Hi Rick, when I got my diesel all I had was super hot air from the defrost. The A.C. would not come on. I took it to have it looked at and the guy filled it with 3-4 cans worth. He said a fuse was in need of a little polishing, and the fill plug was on cockeyed. He fixed me up, and I had the most incredible A.C. until the compressor siezed on me.

Patsy

You might check all of your electrical connections/fuses for a loose contact. You should be able to tell if you are low by the sight glass too.

from the breather "elbow" by putting a real thin layer of "Ultra Copper" on the valve cover connection and then sliding the elbow down on it and letting it set for 24 hours. Put it down near the valve cover to prevent any from going up into the breather tube. You can reposition the elbow as needed immediately after sliding it down.

Now no more leaks from this area. Ultra Copper works great in this application because it is easy to clean off and reapply.

Jim
'85 300D
'95 E320
'97 CRV

Jim, I will have to give that Ultra copper a try. It's made by Permatex, right?
Patsy, I was looking at the Chassis CD and there is a low pressure cut off switch for the compressor. So I am suspecting there is a leak and the compressor is not being allowed to come on.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Rick, Had the same problem and got a new black plastic cap and it leaked worse than the original metal one. Purchased a new seal, put it on the old metal cap and the leak was gone. I hate the increasing use of plastic on Mercedes. This has been said many times before, "Don't make them like they used to."

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Richard Seaman
1982 300D Turbo 198k
1987 420SEL Sold
1993 400SEL 123k
MBCA Desert Stars

Where can I get Ultra Copper?
P E H

P E H, you can buy it at any automotive store. You should find it in the sealant section.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member