blue smoke...again!

[jan lauwers]

Gentlemen,

About 2 years ago, shortly after doing a full motor revision, I had a problem of blue smoke. That problem got resolved easily by replacing the plastic seals on the valves shafts. (see pic). Now, 3 years later, my blue smoke problem is popping up again. The annoying thing is that the smoke does not always appear. It usually happens during longer hauls, i.e. after doing some 50 kms or so. Since it is not always smoking, the seals on the valve shaft can't be the root cause this time... I can't figure out why smoke would only start after driving a while. If oil is sucked in and burned, it should always happen, no? Any thoughts please?

Thanks guys

[Cees Klumper]

Maybe start with checking the compression on each cylinder, see whether there is anything obvious there. Double check the valve seals, just in case. Strange indeed that the issue only appears after longer drives.

[rwmastel]

Did you change anything before this started?  Different spark plugs?  Use oil of a different weight?  Anything?

Do the spark plugs indicate rich fuel condition?  Are they oily?  Regarding "long runs", maybe some component needs to heat up enough to allow the (assuming) oil to get in and burn.

Blue smoke at all times, only pulling away from a stop?

I don't remember if it is all cylinder heads or only specific types, but the post (stud? ball?) that the valve rocker arm rests on can be loose and allow oil to leak past.  Someone with a better memory can elaborate on this.

[Charles 230SL]

...shortly after doing a full motor revision, I had a problem of blue smoke. That problem got resolved easily by replacing the plastic seals on the valves shafts. (see pic). Now, 3 years later, my blue smoke problem is popping up again...

hello Jan, I'd double check the valve seals as Cees recommended. Was the head rebuilt when you rebuilt the engine? If your valve guides and stems are worn the new seals won't last long.

[Benz Dr.]

Check radial play on the valve guides. Overall play indicates general wear, side to side wear indicates rocker geometry problems.

[jan lauwers]

I am so desperate that I am relaunching the same question. This problem is still not resolved. The big mystery is that the blue smoke only appears occasionally, usually on the somewhat
longer journeys. The suggestions that you guys have kindly made in the previous posts have not helped.

My mechanic is a very experienced guy who grew up with these engines, and he too has no explanation for the fact that the smoke is not permanent. He is now going to open the engine, perhaps an oil scraping ring is failing... but even then, the smoke would be permanent, no?

Ideas welcome, obviously.

Thanks gentlemen.

[Paul99]

OK, a very long shot..... I seem to recall that there is a valve on the auto gearbox which (if worn) can allow transmission oil to be sucked into the engine and burnt.  Very unlikely but it is possible.  I recall replacing mine a while back. Sorry but cant recall the exact details but I'm sure someone knows it.

Hope that helps to eliminate possible issue.

[jan lauwers]

Paul,

What you say is correct, but mine is a manual, so I can exclude that cause. Thanks anyway for reacting.

[stickandrudderman]

OK, a very long shot..... I seem to recall that there is a valve on the auto gearbox which (if worn) can allow transmission oil to be sucked into the engine and burnt.  Very unlikely but it is possible.  I recall replacing mine a while back. Sorry but cant recall the exact details but I'm sure someone knows it.

If the modulator valve diapragm fails the engine will suck in the transmission fluid and you will have a huge and permanent cloud of white smoke; I mean huge like a smoke bomb! There's no mistaking it.

[Benz Dr.]

Could be leaking exhaust ball studs. You won't see oil fouled spark plugs because the oil is being burnt in the exhaust stream so reading plugs wouldn't be much help.

Leaking intake ball studs is something you can see but not exhaust ones.