1990 300 SE
 

Hi, Guys....I have a chance to buy a 1990 SE, with 130, 000 miles on it. People said the smog pump froze up, and broke the serpentine belt. Is this an interference motor? Any problems I could run into?
Thanks,
jim

Unless I do not fully understanding your question; the serpentine belt drives the accessories; smog pump, PS pump, AC, alternator, and the water pump, from the crank pulley, externally. Your car has an internal timing chain that articulates the cam shaft via a set of gears; one on the crank, and one on the cam. A broken serpentine belt SHOULD have no effect on the valves or any other internal engine components, even in an interference engine set up.

Just replace the belt and smog pump....and it should be good to go. At the very worst it might have damaged the belt tensioner/plastic pulleys....but probably not. You can skip the smog pump if you remove it and install a belt from an older car (pre-1990). They did not have the smog pump so the belt was shorter.

My Bad...
 

Hi Jim,
It was a good question, and like you I’d rather ask first; then live with the consequences later. It’s tough to buy a used car, and even tougher to buy a used Mercedes. Depending on your location it’s sometimes tough to find a qualified reasonable mechanic, and you can’t just get parts anywhere. The good news is that car has the Mercedes 103 engine, which is a pretty straight forward and solid machine. You only have six cylinders to worry about, and in the 126 chassis there’s plenty of room to work. There are lots of good used parts available and if you’re resourceful and a little bit handy with a wrench it can be a great car to drive. The forum here has loads of information on that model to help keep you informed. Check the archives, there’s always an answer. pawoSD offers some good advice and if the smog pump and belt is the only thing keeping the car off the road, it should be an easy fix. I drive a 1990 300SEL, and keep it going with the help of the good guys on the forum, used parts whenever I can and some new when I have to, and busted knuckles from turning a wrench. Good luck, and let us know if you join the 300SE club.
Kind Regards