Originally Posted by oilslick

I did the unthinkable and bought a 1991 350SDL with 268k on it. She runs very smooth and no smoke. The car is clean and everything works on it. I have never ridden in or driven a better Mercedes. I bought it cheap enough so I could pursue some options should it be a dud.

Even though she's as smooth as silk and doesn't smoke, even when I push her, she IS using some oil. A new valve cover gasket reduced the oil loss significantly but she still goes through a quart every 1,000 to 1,500 miles. There is oil getting into the intake and seeping around the rubber boost connection and at the over boost protection relay. When tubing from the filter housing to the turbo is removed there is oil puddle in the turbo intake housing lip. I put new seals in the turbo and this did not solve the issue. Removal of the oil filler cap while the engine is running shows no blowby. I know that is NOT the most definitive test but a layman's way of testing. I held my thumb over the vc vent tube to air intake tube while the engine was running and it did build pressure but no engine shut down occurred after a good while.

This car is not a necessity for me so I don't really need to do anything to it to protect any "investment." I'm NOT going to obsess over the car. I have access to a short block from a 3.0 SDL and will over the course of time piddle with the car should it die on me. I also have a very strong, smooth running, healthy 5 cyl in an old '84 SD that I'd consider putting into the '91 just for kicks. I haven't found very much info on here in the archives that deals with putting a 5 cyl turbo engine into a later model w126. Any pointers?