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.