I have been driving this '81 240D for just over 3 weeks. On the 3 "long" runs I have made, I have noticed some odd behavior. Let me know what you think. After running at freeway speed (70-75 mph) for just about an hour, I can hear and slightly feel what appears to be a cross between a backfire and a loose drive train or suspension component. This noise will remain until I stop for just a minute or two, and then it disappears. I haven't had the opportunity to continue long enough to see if it reappears or not. I do know, that if I drive for 2-3 hours, but not at a constant high speed, the noise never appears. My first inclination is that it has something to do with the exhaust system, and that extended high rpm driving is creating some sort of blockage, or increased exhaust system temperature that is affecting the exhaust pressure. The exhaust system itself seems to be fairly well aged, but before I go yanking it out, I'd like to make sure that is the problem. My mechanic is not really inclined to go on a two hour road trip with me just to hear the noise. Anyone run into this before? And, if you do think it is exhaust related, what is your recommendation on replacement components that might be with me for awhile. Thanks in advance.

Bud

 

Perhaps the driveshaft carrier berring is getting hot and binding????? They seem to wear out and start to dance around.

Good luck!