Oil Coming Out Rear Exhaust Manifold

[twoods]

My 71 280SL suddenly began smoking and oil leaking from the rear exhaust manifold where it connects to the tail pipe. The engine runs OK without missing or knocking. I pulled the last three plugs and No 6 was black and oily.

Does anyone have a thought on what happened or what i can do to find out?

[al_lieffring]

If it has an automatic trans, check the modulator valve, it could be sucking transmission fluid through a ruptured diaphragm into the intake at the #6 cylinder. The other possibility is an exaust valve guide has come loose.
Take the vacuum line off at the transmission modulator and see if oil drips out.

[Bernd]

I assume you have checked the head gasket too?

[Atazman]

Another possibility is that the intake valve guide on # 6 cylinder has pulled out of the head, thus sucking oil into the cylinder.  To find out you would need to remove the cam cover, remove the rocker arm on #6 intake valve, remove the valve spring, and see if the guide is loose in the head.  But.... getting the valve spring removed requires some special tools and you run the risk of dropping the valve down inside the cylinder without lots of precautions.

[Shvegel]

I second AL's comments about the Auto trans modulator diaphragm. There is a small vacuum line attached to the top of the intake manifold at the rear. If you remove this line and plug the hole and smoke goes away there is your problem.

[Atazman]

Have you found out what your problem is yet?  keep us posted so we all can learn.

Thanks.

[twoods]

Great call! Ran engine briefly, removed vacuum line on intake and found transmission fluid.
 Any tips on replacing diaphragm? Appears exhaust needs to be removed
and possibly lowering transmission. Thanks for your help.

[Atazman]

Thank you for the update.  Glad you found the problem.

[menesesjesse]

I did this with the tranmission out.  You will definitely need to lower the transmission.  The clearance is tight so I would suggest removing it all together.  The are some small parts that are easy to drop.  Also the will need to torque down the piece that houses the modulator.  Do this wrong and a leak may be the result.  With all the work to lower the transmission it would only be an hour more to remove it.  You can get a good cleaning in while it is out and even go as far as replacing the front seal.  Overall I think it will be very tough if the transmission remains in the car.