White Smoke From Exhaust, 1970 220

[Coastal220]

On occasion, and only on occasion, I will get some white smoke from my exhaust on start up, it only occurs about a minute after start up, and it only lasts for about 30 seconds to 1 minute.

It is white, not blue whatsoever, and I am not losing any detectable amount of coolant. I cannot really detect much of an odor, it smells like exhaust, maybe a little bit gassy but I really don't suspect anything odor-wise.

From what I've read here and there it sounds like it's probably the valve seals. I thought I would check with you guys anyway and see if this could be something else...

w115 1970 220, gas, Redline Oil

On an unrelated (but perhaps not) note. The old owner mentioned he would put marvel mystery oil in the tank every 6 months or so. I'm sure there is some controversy about this, but do I want to continue this practice? Could this help this startup smoke? So many of these things sound totally gimmicky, but this guy seemed to really know what he was talking about.

[Mike D]

White smoke can be coolant, transmission fluid or brake fluid. If the smoke is a very pale blue it will appear to be white. Are any of the three fluids showing a loss in their levels?

[Coastal220]

I'm seeing no loss of coolant or transmission fluid (though I cannot be absolutely sure about the transmission because I do have a very small leak from its rear seal). Transmission is manual. I am noticing no loss of brake fluid.

I will start tracking this more carefully, though the transmission will be difficult to notice with any accuracy for the above mentioned reason.

I suppose the smoke could be a pale blue, but whatever the case it looks very white to me... How would it be possible for me to be burning off brake fluid?

[Mike D]

Eliminate the transmission. I didn't know it was a manual.

Brake fluid can be pulled through the vacuum diaphragm if you have a leaky master cylinder. The surest way to check for a brake fluid leak from the master cylinder is to slide it forward on the two mounting studs and look for moisture. Many times you will notice a trail on the outside of the vacuum booster but this can be hard to spot with how they are mounted on the W114's/115's.

I had a BMW 2002 which only smoked when doing a hard left turn but when it did it laid out a smoke screen. Took me a month to figure it out. The leak was very small and until the fluid accumulated in the booster it would never smoke. Hard left the fluid would slosh over to the vacuum line and then, instant cloud!

[Coastal220]

Mike, thanks for this. I'll take a look at this and check back. I'm glad you're not telling me it's the valves.

Cheers.

[Mike D]

Originally Posted by Coastal220

I'm glad you're not telling me it's the valves.

Yet!

[Pooka]

This is a residue of some sort that is burning off when you start. It is taking place all the time, but there is only enough of it to smoke when you start up and the plugs burn it off.

I am betting it is the valve seals. They are leaking oil past them when the engine is shut down and it is pooling on top of the pistons. When started it all burns up at once and comes out as white smoke.

You can remove the vac line to your brake booster and see if continues to smoke. You will then have manual brakes, but you know this going into it so you know the first stop will take a great deal more effort. If this stops the smoke then you will need to replace the booster since it is leaking inside.

The good thing about the valve seals on a Mercedes is that they can be replaced without removing the cylinder head. This takes a shop that knows what they are doing, but if someone is in the Mercedes repair business they should know how to do this. It is something best left to an expert, but you could do it yourself if you are VERY mechanical since it involves removing the camshaft (which is easy) and then replacing it (which takes forever to time and set valve clearances) but it can be done.

Another good thing is that these parts are not expensive. There may be a bit of labor involved, thought.

[Coastal220]

Removal of the camshaft? I am under the impression valve adjustment does NOT require removal of the camshaft.

[vandor]

Could it be just water vapor from condensation in the exhaust?

Csaba

[Coastal220]

It could be... which is just the thing, it's not so smokey that I can't rule condenation out. And so far it hasn't been warm or hot enough for me to know that I shouldn't be getting this effect. Nonetheless, it seems to have a more smoke-like quality than that of condensation.

[Govert]

Water will condensate in the engine as well during starting, that can cause white smoke during the warm-up phase when the water evaporates.

[Pooka]

Originally Posted by Coastal220

Removal of the camshaft? I am under the impression valve adjustment does NOT require removal of the camshaft.

Correct.

But replacement of the valve seals will, and when the camshaft is replaced it the valves will need to be adjusted.

[Pooka]

Originally Posted by Govert

Water will condensate in the engine as well during starting, that can cause white smoke during the warm-up phase when the water evaporates.

But it will not smell like oil or have an oily feel.

One test to do is to let the car sit overnight and then have someone start it while you are back at the end of the tail pipe with a white sheet of poster board.

Let the exhaust run on the board until it clears and then examine the board. There will be water, which should be clear, and there will be some soot, which should be very black, and that is all. If there is an oily residue it is time to consider the brake booster or the valve guilds. If the water has a greenish tint to it then you have a leaking head gasket.

By the way, the only way the brake booster can be letting fluid leak into your intake is if you have a failure of the booster AND your vac pump. Since this is a diesel and develops no vacuum you would have to be pulling the fluid in through a very worn system.

QUESTION>>>>> When you shut off the car does it run on for a bit? If so you might have worn rings that let engine oil pass the piston rings and settle into the combustion chamber. This is not common, but when you wear out a set of rings in a diesel engine it is possible, and this could also be the source of your smoke.

However, worn rings normally smoke all the time.

[Pooka]

And one easy thing to do is to hit the auto supply shop and pick up a can of anything that claims to stop smoky engines.

These chemical work in two ways: They thicken the oil so it will not flow down past the valve guides and they swell the 'rubber' seals in the guilds so they seal up tighter.

Many Mercedes of this era have bronze valve guides, and if this is the case this stuff will not swell the bronze but it should thicken the oil.

Adding a can of this stuff to your oil has the advantages of being cheap, quick and unable to do anymore harm. If it diminishes your smoke then you know you are moving towards the solution.

[Coastal220]

Originally Posted by Pooka

But it will not smell like oil or have an oily feel.

One test to do is to let the car sit overnight and then have someone start it while you are back at the end of the tail pipe with a white sheet of poster board.

Let the exhaust run on the board until it clears and then examine the board. There will be water, which should be clear, and there will be some soot, which should be very black, and that is all. If there is an oily residue it is time to consider the brake booster or the valve guilds. If the water has a greenish tint to it then you have a leaking head gasket.

By the way, the only way the brake booster can be letting fluid leak into your intake is if you have a failure of the booster AND your vac pump. Since this is a diesel and develops no vacuum you would have to be pulling the fluid in through a very worn system.

QUESTION>>>>> When you shut off the car does it run on for a bit? If so you might have worn rings that let engine oil pass the piston rings and settle into the combustion chamber. This is not common, but when you wear out a set of rings in a diesel engine it is possible, and this could also be the source of your smoke.

However, worn rings normally smoke all the time.

Thanks for these suggestions Pooka. I will do the paper board test--very cool. This car is a GAS, which I should have mentioned if I didn't in the first place--my apologies.

For what it's worth, the car does have some run-on but this is, I believe, due to a bad shut-off solenoid on my carb that I just haven't gotten around to replacing. I kill the car by letting the clutch out in fourth, with the brakes applied, and flipping the key as it begins to die. Come to think of it, could THIS be encouraging brake fluid to be sucked back, especially if the booster seal has failed?