Top end rebuild m114.011
 

Hello all, just got home with a 1971 250. noticed smoke and tapping., got a good deal so took it anyway. as i look into everything i am pretty sure it is a head gasket. Plan on doing a quick rebuild with new gasket, studs, valve lap, valve stems. done this with many of cars, but first mercedes. anything to be cautious of? any "must do's" while in the process?
car has great oil pressure, no noticeable oil consumption.

Thank you,
Donny

dl:

Although the chassis is a W114.011, the engine is a M130.923. (stamped in top of block, next to distributor)

That said, inspect carefully for loose valve guides, worn out cam lobes/cam followers, worn timing chain, worn chain guides, loose or inop chain tensioner.

Re: Smoke
Remove the vacuum line from the modulator (right rear of trans), check for the presence of ATF. If the modulator diaphragm is leaking, ATF will be drawn into the intake manifold.

thanks, noticed that when i starting looking into parts. motor pulls strong, drove 25-30 miles after topping off antifreeze. did not notice a drop, it is smoking pretty bad though

Hi Donny,

What color is the smoke? White smoke would suggest water through the head gasket, black smoke could be valve guide of piston rings?

Tapping could be valve out of adjustment?

Please let us know what the issue turns out to be. Other folks will follow this thread in the future looking for clues. You will be contributing to the knowledge base available when you share your experience on the forum.

Best regards,

Jeffrey

I would plan on replacing the valve guides-they are usually worn out on an old Mercedes. Valve train noise that does not go away after adjusting valves is usually worn guides/cams.

I pulled the head the night I got home. The smoke was whitish. First thing I noticed when I pulled the head was a mark on #5 piston from intake valve hitting.
after I pulled the manifold I noticed excessive build up in the #5 cylinder exhaust.l, and a little build up in #6.
While pulling the valve train out, #5 intake valve guide came right out.
not sure if the problem originated from #5 intake valve out of adjustment or the valve guide floating.

I'm waiting on parts now, just gonna rebuild the head and put the car back together.

The m130 engines need valve guides and rubber seals at intervals. Some cam issues seem to focus on the first lobe being worn. Always spray a little wd 40 on the vacuum fitting on the intake manifold when you get it back together.

A very small air leak there seems to upset the last cylinder very easily sometimes. Also do a torque check on all the valve adjusters with the rockers off.

Any adjuster that torque moves at less than spec. Should be replaced or dealt with to avoid burnt valves. Usually the exhaust valves. Also check for valve clearances at the recommended interval or sooner.

Easier to do these things than have to pull the head again for a burnt valve later. Been there and unfortunately done all the above at one time.