280SE 3.5 white smoke only while warming up
 

I recently purchased a 280SE 1971 3.5 coupe. During warm-up (not when cold or at operating temperature) the car blows lots of white smoke. This only happens if the car is being driven. If I let it warm up before driving the car, there is no smoke. The amount of white smoke is far beyond that from condensation forming in the exhaust. Indeed there is that much it is embarrassing. Any thoughts?

Does it smell like oil burning? I have seen engines so badly in need of valve stem seals and/or guides that they blow thick white smoke rather than just a puff of blue smoke. At other times does it blow any blue smoke? I would also consider oil (or similar) from another source as a possibility (eg. faulty transmission vacuum modulator or faulty brake master cylinder/servo).

Thanks Greg. No blue smopke at any other times. Therefore, I do not think it is the valve stems because the smoke is not blue and it does not occur at startup or when warm. I will pursue the possibility that it is a vacuum to brake or transmission problem. As the problem only arises when the car is driven, I am leaning towards checking out the vacuum to the transmission first.

Cheers
Joe


280 SE 3.5 Coupe

Funky smelling white smoke on warmup is usually the trasmission modulator leaking and sucking tranny fluid into the intake. It leaks in overnight, then burns off as the engine warms up.

To check, pull the vac line at the modulator, it's easier to reach than the intake banjo bolt. If there is any tranny fluid in there, replace the modulator.

Bad thing is that I've never heard of an MB modulator actually sucking out tranny fluid, it works via a separate actuating rod, not inside the tranny like American ones. Not impossible, though.

Check the smell -- if it smells of glycol, you have a coolant leak into the combustion chambers during warmup, possibly via the warmup regulator in the intake manifold.

Could also be sucking extra oil out of the valve covers during warmup, but I don't know how.

Peter

how many miles on the engine? or since the last top-end rebuild?

my guess is that it is valve stems/guides and stem seals.

head ever been off?

if you can find a borescope, put it down spark plug holes and look around. my guess is that the piston crowns have a thick gummy coating.

Replaced the transmission modulator to no avail. The engine has done 221,000 klms (138,000 mls). I do not think that the heads have been off. That said, I am taking it to the mechanic next week and will check compression, brake vacuum, do a bore scope and check the warm-up regulator. Thanks for all the help so far - any other thoughts greatly appreciated. I will keep you posted.

Cheers
Joe

My mechanic resolved the smoke problem by (i) replacing the PCV on the LH rocker cover breather hose and (ii) instaling oil traps. The oil traps are essentially small pieces of mesh that catch the oil inside the rocker cover and allows air only thru the breather hose. The oil accumulates on the mesh and drips back into the rocker rather than going into the breather hose. They are standard on old Fiats and Alphas. I am happy with the result at a relatively modest A$240 (US$160). My mechanic is Rob at Monza Repairs in North Road Oakleigh Melbourne Australia (03) 9576 9341. I can recommend him for anyone in Melbourne Australia with a classic auto (merc or otherwise).

Cheers

Hi jniven
Glad to hear you have solve the oil smoke problem
I have the same problem whit my 350 SL 1971 mod.
The oil trap , du you mont it inside the valve cover or outside, ?
Do you use a trap from Fiat or Alfa? Do you have a part number?
You can see a pictures in this forum I have taken of the problem.
Do you have a pictures of the trap you mont?
Arvid from Norway

Arvid
The traps go inside the valve covers. They are a standard part for Alphasuds and Alpha 33s or Fiat 131, 132 or 134. I do not have the part number or pictures - sorry.
Cheers
Joe