Common issues

[74baja]

Hi all,
I see a 1993 300D for sale. It seems pretty cheap, $3500 with 165k miles. What are the common problems with these cars of this age? Are there any major engine maintenence things? What would be the things to look for when buying one? Also, the ad says it is a 5 cylinder, which I have herd is more reliable than the 6 cylinder. Were the '93s 5 cylinder?
Thanks,
Jack

[Jeremy5848]

The comment on the 5-cylinder engine being more reliable is comparing the OM602 engine (5 cylinders) to the earlier OM603 engine (6 cylinders) that was used in the 1986-87 300SDL and the 1987 300D Turbo. Although any engine can be damaged by overheating, the 603 engine was especially likely to crack its head if significantly overheated. People who "tried to make it home" after losing all their coolant found themselves faced with an extremely expensive repair job.

Mercedes addressed this problem by redesigning the 603 head. The later 602 engine takes advantage of the earlier failures and has a more robust design. Head failures are therefore much less likely, although if you really try . . .

The main thing to look for is evidence that the previous owners have kept up with service and repairs. The seller should have a whole file of receipts. If not, you are shooting craps. Second and third owners of Benzes who cannot do their own maintenance soon discover that Mercedes repairs are expensive and often start to skip things ("I can live without air conditioning"). Your bargain car then turns out to be a pig in a poke.

If you learn to do at least some of your own work and buy parts on line, you can save a heap of money. The trick is to do your homework first. Since I've never owned a Benz with a 602 engine, I'll let others give you a list of questions to ask the seller.

Good luck. Keep in touch with this forum, it is the greatest store of Mercedes diesel knowledge on the planet.

Jeremy

[sixto]

Do a search for gsxr's W124 300D buyer's guide.

Sixto
87 300D

[74baja]

I am having trouble finding gsxr's write up. but i found some other stuff. When do the timing chains need to be done? I've heard that the trannys tend to blow out, when does this happen?
Thanks

[sixto]

See the attachment.

Timing chains should be done when there is more than X-degrees of stretch. X is between 5 and 8 depending on who you talk to. I don't remember what the manual says. The simple measure is to set the cam alignment marks then see how far past TDC the crank pulley indicates. Take the average of several readings. There is no time or miles interval for replacing the timing chain since it's not subject to direction change like in V8 engines and there isn't a history of timing chains just snapping other than in some early W124 602 engines.

Transmission longevity is highly dependent on care and maintenance. Service life can't be predicted. I keep saying 150-200K miles then get slammed by folks with over 300K miles. My 91 300SE had a transmission go with under 150K miles. Other than project MBs with bad transmissions to begin with, I haven't had another transmission go on me and I typically get cars with 200-250K miles on the clock.

Sixto
87 300D

[oldiesel]

Check timing chain as soon as you get it home! some of these cars had catastropic chain failures at mileage that other Mercedes models would not.If you dont feel you can handle checking and if necessary replacing the chain with the info available here perhaps you should chose a different car,if you have to pay to have everything repaired that goes wrong with an old car a Mercedes is not the best choice.To get normal performance from this engine you will eventually want to eliminated the EDS and change to a pressure operated waste gate,again not a big deal if you use the info here and DIY.Otherwise the 602 is an excellent engine and should reliably get you over 30mpg on the highway.Do alot of reading here,just about anything you need to know about these cars is available here along with very helpful people. Don