I have a 1993 318is with 5 speed manual... I have this hollow rattle kind of clunking sound almost at my feet while its running. Ill describe it a little more. It doesn't make any noise while accelerating or simply keeping speed up a slight incline. As long as it has forward pressure on the drive line, no noise. Any reverse pressure such as decelerating, down shifting, or simply letting off the gas while driving, louder noise. Idling at a stop light, noise most of the time, can't really describe when or how loud its just almost random. The sound does increase speed with RPM and doesn't seem to be related beyond the transmission. Pressing the clutch doesn't seem to affect the sound at all, but it makes the same loud noise in reverse as it does decelerating.
Laying under the car I can't seem to detect where the sound is coming from, normally I would thing loose motor mount and the engine itself is hitting against the body, but I can't see any looseness in the mounts nor anywhere it would be hitting. If it leaked oil I would assume it was the rear main bearing.
My car also had this issue with the clutch that seams to have gotten better. It would on occasion, almost at random, sitting at a stop light or parking with the clutch pressed in and the transmission in 1st gear, the car would all of a sudden start going forward slowly and continue to try to go forward until it died or i pulled it out of gear. After stopping again I could pump the clutch as many times as i wanted, the input shaft on the transmission was still turning, and would not stop. In order to fix the issue every time i had to stop the engine, restart it, and everything would be fine again until next time it decided to do it.
Now that my decelerating noise has gotten louder, my clutch problem seems to have gone away. My fluid level is perfectly fine and isn't leaking.
hollow noise... rattle... could be that 1 of those rubber doughnuts that hold ur exhaust pipe in place let go. reach at ur exhaust pipe and shake it... if it shows any indication that it is touching the frame... there's ur prob :-D
clutch problem... the air in the lines may have purged naturally. therefore, no more problem :-)
Well... exhaust isn't touching any body or frame parts... noise seems to be coming from closer to the engine/clutch area. No real vibration though... I'm in the process of removing the transmission to see if maybe theres a loose bolt on the flywheel or something, maybe a bad pilot bearing... with the clutch let out could the pilot bearing make noise if it were bad? the engine and tranny shafts would be spinning at the same speed so I wouldn't think so....?
Yeah... the tranny is down now.. fairly easy job actually, good thing the exhaust didn't have to come down too, I was dreading that part... I found the input shaft on the transmission is loose. ill be pulling the clutch also to check the pilot bearing. I'm not 100% sure this is going to fix my problem, but, it is just another problem... Could that sound hollow being its behind so much heat shield and sound dampening?
Now that the transmission is out... I found some play in the input shaft on the trans, found the 2 parts on the flywheel are moving freely without any spring tension (if there is supposed to be some), the disk and pressure plate are new and weren't loose, the fork and throwout bearing look good but I'll replace them anyways, and lastly the pilot bearing seams in good condition, but may be the wrong size. There is some scratch marks on the input shaft where the pilot bearing goes onto it. Ill know for sure when I pull that bearing. Any idea's possibly?
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