I have a 1987 300 SDL TD with 125K that has an annoying hum(sometimes howl) coming from the rear part of the vehicle. When you tap the brake, the noise stops and may not come back but on the other hand may continue a few seconds after the brake tap. Every time I tape the brake the noise will stop only to start up again.
The vehicle is not driven a lot. I took off the rear wheels and inspected/cleaned the rear rotors and pads. That seem to help for a little while but the hum came back.
About 5 years ago the left rear brake caliper was replaced because it had seized up.
I have had people tell me that the problem is with the brake pads or with the brake caliper not releasing the pressure on the pads. I have had the vehicle for 10 years. Another person told me that the brake fluid needed to be changed and that was causing continued pressure on the pads. I have checked the rear wheels by touch and do not sense any out of the ordinary heat build up.
I would appreciate help from anyone that has had to deal with this issue.
Thanks.