I recently have a strange problem with my W126 380SEL. When the car go down hill for a long distance (3 Kms or more), once the car is level out, it gives a lot (I mean a lot) of white smoke for only about 10 seconds.

I strongly believe it is coolant burning because the coolent level will drop after that.

I also find soem coolent stain near the thermostat.

Am I up for a big repair bill? Please help.

Regards,
Michael Tse

Your symptoms are classic. They almost universally describe the syptoms of bad valve guide oil seals. It also is classic for a bad diaphram in the vacuum modulator of the automatic trans.

What makes this the answer is that during the drive downhill manifold vacuum is the highest ever, often reaching 20inches or more. This sucks the oil in through the guide seals or diaphram.

I know of no such a case involving coolant.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Maybe I have more than one problem.

Firstly, the car does use a bit of engine oil - 1L per 1000Km. There is also some oil leak. However, the smoke was dense white rather than black if it was burning engine oil.

Secondly, the automatic transmission oil does not seem to go down at all. However, the technician did say there were soem deposits on the pan last time (1 week ago) he service the auto transmission.

Do those valve guide cost a lot of money to repair. Should I keep the car or simply upgrade it.

Many thanks in advance.

Regards,
Michael Tse

Mike,
If the smoke is dense white like what you said its
anti freeze or coolant leaking to your combustion chamber.
If your burning oil the color is sky blue and if its black
your running rich.My wild guess is you have a cracked cyl.
head gasket.Or cracked cyl.head as well.
Does the car over heated before this happen?

Clauser1

Actually when you talk about overheat. It does overshoot to about 100 deg before falling back down to normal 80-85 deg.

It has been doing this for a long time (2 years). I changed the thermostat and flush the radiator a few times with different people but nothing works so far. I have given up.

For the smoke, it is dense white and I relly think it is coolant because the coolant level will go down significantly after these white smoke problem occurs.

The car also gives a bit of black smoke under full accelaration (5000-6000 rev).

I love the car and really want to keep it. I hope all these problem can go away soon.

Regards,
Michael Tse

Mike,
Have you noticed your engine oil color?
If its cream&coffee combination,most
likely you have a cracked cylinder head.
If its normal in color,you definetly
need cyl.head gsket.
Hope this help.

Clauser1

I really don't know why I'm back on this post.

I suppose since you all want to think coolant when the story says otherwise, I should advise you to stand behind the car and smell the cloud. If its a "white" cloud of oil smoke (as anyone who has ever seen this much oil smoke would call it), it will smell like it. If its coolant/water it will smell totally different.

MB V8s have well known valve guide oil seals problems. They also are well know for being the last motor in the world to get a head gasket problem. Since your oil consumption indicates that you have a V/G oil seal problem you might just have it fixed since it is relatively inexpensive. Then, since your cloud will have disappeared you can look for your coolant leak.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Well, the engine oil color is normal. I must say I need to top up 1 litre every month.

Thanks so much for your help. I know the gasket is not too expensive but it is a big job to change the gasket.

Also, while I am fixing this problem, are there anything else I might need to pay attention to at the same time.

Many thanks....
Michael Tse

Thank Steve, I will definitely fix up the V/G.

Again, thanks so much for your help.

Regards,
Michael Tse