Just bought '87 300TD. Numerous issues. HELP!
 

Good day, all.

I just picked up a 1987 MB 300TD with 228,317 miles. I am new to diesel, and haven't owned a Benz in over 30 years, so I am clueless with what is wrong with my car.

Here are my concerns:

1.) When car first starts, it idles rough and is very noisy (normal diesel noise?). As soon as I get driving down the road, at 1100 rpm or so, the engine quiets right down. Is this normal?

2.) Car idles rough. Doesn't stall, but acts like it wants to. It also seems to chug/lose power momentarily when driving down the road. Doesn't happen all the time, but it can happen at any speed, even at 65 mph. The air filter is clean, and I have just replaced both fuel filters. No help.

3.) Electrical problems - cruise control works/shuts off when it feels like it. Climate control turns on and off, even when it is shut off. Fan will turn itself on, a/c compressor turns itself on/off, all this when the unit is in the "OFF" position. Everything else seems to work.... horn, lights, turn signals, wipers, etc. It does have an aftermarket stereo. Don't know who or how it was installed, but it was supposedly done "professionally".

4.) When closing the sunroof, the air deflector doesn't retract down automatically. I have to hold it down and pinch my finger! Is this a major fix?


5.) Any tricks to getting the 3rd row rear seat to fold down? It seems hung up on the driver's side. The owners manual is worthless in telling how to do it. I have removed the bottom cushion, to no avail.


Thank you for all your patience and consideration. A lot to ask here, but figured I may as well ask it all in one thread rather than making multiple threads.

Thank you for your reply, but can you explain please? I don't understand how a bad glowplug would affect idle or engine performance at 60 mph. My understanding is that the glowplugs are only used to start the car, and that once started, they shut off completely.

Rough cold idle is generally caused by glow plugs, they cycle on and off during warm-up, but I don't see how they can be an issue at highway speeds either. If it idles rough after warm-up, I would be looking for a leak in the fuel system, around the fuel filter, and the return lines that jumper between the injectors are common on just about any diesel engine. You might also check the lift pump and see if it is delivering a constant supply pressure

Totally ignorant about most issues and rely on this forum for what most consider dopey questions, but had similar issues on an '85 300D when I bought it. Replaced all glowplugs which helped on startup and then had valves adjusted-major difference in how the car ran and eliminated rough idle. Maybe will help

1. You need new glow plugs.
2. You probably need a valve job.

2.) Car idles rough. Doesn't stall, but acts like it wants to. It also seems to chug/lose power momentarily when driving down the road. Doesn't happen all the time, but it can happen at any speed, even at 65 mph. The air filter is clean, and I have just replaced both fuel filters. No help.

Found and fixed this problem. There was a leak in the return line to the fuel tank. It was sucking air. Runs great now.

Exactly the problem. Thank you, oldrebuiltdodge!!!