Hi. I'm new to the diesel world and the MB world. I am an experienced mechanic from years back and this car is different than any other I have ever worked on so I have a few questions and hope I didn't screw myself buying this car. The most worrysome is I have a noise in the driveline that sounds sort of like a bearing going out but I have not yet been able to pinpoint it's location as the car has to be rolling about 30 or above to really hear it. It kind of sounds like you're driving on knobby mud tires. The sound pitch changes upward with speed increases and downward as speed decreases. I had it on a rack and I have checked all wheels and the driveshaft but don't feel anything abnormal such as roughness in the bearings. Can the transmission be making this noise? The noise remains even if I shut down the engine and coast in neutral. I am stumped and worried.

Aother problem is the A/C doesn't work. I can short across the pressure switch at the receiver/drier and the compressor will only run for a second or two then never again unless I shut down and re-start the engine. I'm guessing the climate control module is bad but I don't even know where it is located. I also do not know where the relay is at. The blower will run and the heater functions but the A/C compressor clutch will not stay energized. AFAIK it still is the R-12 and will probably need conversion to the new stuff.

Finally this may not be a problem but I really don't know. Acceleration from a dead stop is painfully slow untill the engine spools up above 2K RPM then it finally begins to make power. Above 3K RPM the power is real good. Is this normal on a 3 litre turbodiesel?

Thanks,
Steve

 

The noise may be front wheel bearings or a flex disc on the driveshaft. These cars are really noisy when the wheel bearings start to go. The flex disc is a rubber coupler on the drive shaft, there is one behind the trans, and one at the rear diff. The climate control module is probably bad, that is a common issue with these vehicles. If you remove the module, which is the in-dash unit with the push buttons on it, sometimes you can repair it by resoldering the solder connections on the circuit board inside. There are also two sensors on the engine that control the compressor. One is on the waterneck, it's a little brass sensor with one wire on the top. to test it, unplug the wire and see if the compressor runs. The other is on the throttle linkage ,it shuts the compressor off at full throttle. Either of these can cause the compressor not to run. My 1987 SDL is a dog off the line too, they are fairly heavy cars.

Hope this helps,
John

 

Thanks for that info John that does help a lot. Much appreciated!

Steve

 

Slow off the line is an understatement for a diesel benz. My 190d turbo is the slowest car I have ever driven off the line but has some serious power at 3000 rpms. I am going to do a 5 speed upgrade and find some way to get more boost at a lower RPM and that should get some more power off the line.

 

Desert Dog,

You might want to educate yourself about the ALDA, which restricts fuel flow into the engine until boost builds to a particular point. This may be of help to all that have acceleration issues from dead stop.

 

Thanks for that info and link Dagobx. Good stuff there!

 

DD, glad to help - hope it works out for you.

 

I had the same problem with the A/C. It is a faulty Klima relay cutting out. It is located near the firewall next to the Over Voltage Protection Relay. It is expensive to replace, $120+. The climate control is OK if the A/C comes on then cut itself out.

I put a small relay in there and by-pass the electronic, only the signal from the CCU is monitored. It has been working for 3 months now without issue. The downside is that it does not monitor the spinning of the compressor. It if does jam then the engine may chew up the belt. I take that chance. There are other downsides like monitor the kickdown relay but I do not care much for that.

 

Well the noise I was worried about turned out to be the front wheel bearings so I fixed that and drove a nice 500 mile trip. I also noticed the engine is now running much better. I'm guessing the cat converter was sooted up and robbing flow. Still haven't fixed the A/C yet. Saving up for a new clima controller....

I have noticed some soot blowing up onto the #2 injector. Upon closer inspection, it looks like someone put in timeserts that the injectors screw into and the soot is conbustion pressure leaking past the locking pin of the timesert. I hope this is not a major problem. Seems to run fine so I'm going to have to keep driving it for now as it's my only transportation.

Do the valves need to be adjusted on these things or are they hydraulic. I have what seems to be a tappet that sounds loose but I haven't nailed down where the sound is coming from. Mostly I can only hear it at idle.

Thanks for the help guys!