looking for a new (to me) diesel benz - Page 2 - PeachParts Mercedes-Benz Forum

jivadent · #16 07-18-2004, 09:18 PM

Ok Alex, now you got me worried... is there something I don't know about the '91 350SD?

AlexTheSeal · #17 07-18-2004, 09:36 PM

Just search for 350SD on the forums and I'm sure you'll find plenty to read.

I don't know the whole story off the top of my head, but other people may be able to fill in the details. The 3.5 liter diesel is notorious for a design problem that led the engine to self-destruct. The first symptom is greatly increased oil consumption, smoke, loss of power, etc.---the general symptoms of a worn-out diesel, except this could happen at any time, sometimes after only 50K mi or so.

Mercedes offered new long blocks under warranty to those whose engines blew up, and the problem was supposedly fixed in the new motors, but any car with the original engine (or with no records) should be considered a time bomb.

Sorry to be the one to break it to you.

jivadent · #18 07-19-2004, 01:14 PM

So I spent about 3 hours yesterday reading about the 350SD on here and other places. I found about a dozen people complaining about the rod bending.

I talked to my mechanic today, and he said he's heard of the problem, and that it is more common than it should be, but that he's come accross 40 or 50 of these cars, and he's never had one that has had the rods bent, and all had original engines. He said he thinks they're great cars. If 1 out of the 50 had the rods bent, that would mean a 2% failure rate.

I told him that from the research I did on the net it seemed like a 50% failure rate, to which he laughed and said that Mercedes would've definitely done a recall if the rate was that high.

So this alleviated my fears a good deal. I'm sure one reason you hear so much about these cars is because they're not supposed to fail, so when they do, the owners are very vocal about them. Another factor is that owners of later model Benzes are probably not as much do-it-yourselfers as the early to mid 80s owners. So the ones that do own them that don't have problems, are going to be a lot less visible because they wouldn't frequent forums like this.

I hear that around 2500 of these cars were released in the US. Take the dozen complaints that I found (from a comprehensive internet search), and quadruple it to make up for those that didn't complain for whatever reason (no net access, didn't care, were satisfied by their dealer, etc)... that's a 2% failure rate.

So it seems (and I hope I'm right) that this problem isn't as widepread on the 350's as people make them out to be, although it definitely occurrs more often than it should.

AlexTheSeal · #19 07-20-2004, 01:59 PM

Well, I hope you're right. To me it just seems like too much of a gamble. OTOH, some people say the same thing about the early aluminum-head 603s, which I love and have had no problems with. To each his own.