Smile

Head gasket was changed last year, Overheating problem was solved by changing a new radiator but now coolant starts to leak into the engine AGAIN. A qualified MB mechanic opened the head and found out problem is the block. It will be too expensive to take the block out, take it to a machine shop to level it ( I believe the mechanic said because of overheat, the sixth one is dented,the machine shop will wield something on it then shave it to the same level). I really don't understand how the machine shop do but I do understand that the block and the head must be level and smooth in order to put the gasket between, then the coolant will not get into the engine.
If this way of fixing the coolant leak is too expensive, can I go to the junk yard to buy an engine to replace it? I read in the forum that there are not that many 1991 350SD produced, if that is the case, what other more easy-to-find engine can I get. Or I should say what year, what model's car engine is compatible.

DubVBenz

Try to get a mechanic to swap an inline 5 3.0 liter diesel from the older models. It will be slow as a dog, but bulletproof.

Smile

I'd read that 86,87, 300D are the easiest to swap? Is that right? Or should I just take the block down to fix it (cost 6k, is it worth?)

TMAllison

Go to Peachparts and search posts by by member "Sixto". He did the engine swap on a W140 ~5 years ago. Donor engine is a 603 as I recall. Reuse the orig head and IP and it ends up being a ~3.2L.

Rebuilding the 3.5L is a waste of time. Even the crate motors MB put out to fix their rod/crank mistakes didn't work flawlessly. Usually considered to be the worse engine MB ever made.

Smile

Thanks, I contacted "sixto". He gave me lots of options and good advise.