Hi,
I am totally new (this is my first post) so forgive me if this seems vague or redundant.
My car is a 1986 190D 2.5 A/T that burns B99. I just bought it a month ago and this problem has been apparent since the first day.
The problem is "grinding" at the 200-700 rpm level. When idling it's fine. Once I accelerate past say, 1000 rpm it's fine. It's only at the low rpm that the sound occurs. It's almost as if it occurs harmonically.
On the test drive this did not happen. On the way home I filled it up with diesel because I could not find B99 and I was running real low. I have run B99 ever since. I got on the freeway and drove about 30 miles to have my oil changed. After the oil change the sound started. Now I have theorized that the sound was happening regularly before (with the former owner) but only when driven to a certain temperature or distance which in the test drive I may not have done. My other theory was that the guys at the oil change place may have left a bolt loose on the skid plate or something. When I returned I made them go over it and the sound is still there. Performance is not affected. Its an old car with 206K and a daily driver so it has some quirks but generally a strong runner.
Any help or thoughts appreciated.
- geoff

Does this happen when sitting still, and you operate the linkage from under the hood, or is it when you drive?

Also, is the A/C on or off?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

When operating the linkage under the hood as well as when driving. A/C is broken or doesn't work. I have not troubleshot the A/C variable.

Thanks!

Does this car have any heat shields or belly pans? I've seen gravel in heat shields that would cause that. Could be something loose. How are the engine mounts and the fan belts/tensioner?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

mounts seem fine- belts seem snug - unable to see anything loose in skid plate/heat shield
*edit*Just got out from under the car and everything is intact. Tightened up a loose bracket on the heatshield but it made no difference. When I cranked up the engine the belt seemed to vibrate at the same time I heard the sound. Not sure what the tension should be but there is about 3/4" of play in the belt. I am thinking it has to do with the A/C compressor - if not then it's either the water pump or the alternator but coolant flows well and the alternator functions fine. The power steering does squeak when turning the wheel but seems to work fine.