Chug chug chug noise....solved

[youngbimmer]

So I'm trying to wrap my mind around where this "chug chug chug" noise is coming from when I accelerate. It almost sounds as if there is something stuck between the wheel well and the tire, making contact, as the chug chug noise gets faster and faster as the rpms rise. No noise in park/neutral at any RPM, only when moving. Anybody got a clue? I inspected underneath to see if something is stuck or contacting any of the wheels, but alas nothing. m30/auto trans build date 12/14/87

[CroughtonE32]

Check your heat shield near the Cat. I had that noise many years ago and a simple bend made it all better. Good to see you back "youngster". Nobody will ever forget "the fire story". It will live on in infamy!

[youngbimmer]

D'oh, I should have looked at the cat heat shield.....I had to cut mine off my RSX because it had corroded and would rattle like all hell. The rattle noise is not consistent either, comes and goes, seems to be worse when cornering. Thank you for the tip. The fiery mess has left me ultra paranoid for anything and everything. I went to start my car today, it would not start. Battery voltage was low at 11.46, and there was tons of whitish corrosion in the battery pan. Guess what wasn't connected? No vent tube....not sure if that has been the problem but I was not taking chances, replaced immediately, cleaned the battery pan, hooked up the vent tube, she fired right up. I checked voltage while she was running, not sure if 13.6 is ok with lights/heater on/13.9 without accessories running, seems kind of low to me, maybe alternator is old should be replaced?

[CroughtonE32]

Those alternator numbers are just fine. I would charge the battery up to full capacity, if it can take it. Battery should be over 12.5 or so with motor off. Could be that battery just wont charge over 11 and change with a good alternator. That would mean a new battery. You can't live a life of car paranoia because of that fire. People say you can never get struck by lightening more than once. 25 years ago I was walking in a parking lot in South Miami and the tip of my umbrella was hit. Burned up and knocked me to the ground. That's why I don't care if it's thundering and lightening outside. I get the mail anyway. I tell the wife, I'm never gonna get hit twice. Neither will you.

[shogun]

or something stuck between the protection plate and brake disk http://www.realoem.com/bmw/enUS/show...diagId=34_0035
Once a stone hit my protection plate and it was then touching the brake disk, had to fix it

[SergeBMW]

It could also very well be a collapsed driveshaft center bearing. This causes the driveshaft to fall low enough to where the rear U-Joint will hit the heat shield (keep thinking apollo CM when I say that) and cause it to make that noise you are describing. Had that issue with my car and had to swap it out.

[m60power]

It could also very well be a collapsed driveshaft center bearing. This causes the driveshaft to fall low enough to where the rear U-Joint will hit the heat shield (keep thinking apollo CM when I say that) and cause it to make that noise you are describing. Had that issue with my car and had to swap it out.

I don't think the heat shield on our cars is adequate to survive a trans-earth injection re-entry from lunar orbit

[haynes740]

I have a similar noise when I sit to long in the drive through. i feel like one of my rear brakes is not fully releasing. Worth a check

1991 735iL


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[youngbimmer]

Thought I'd follow up on this thread. Problem is solved. Culprit: Center support bearing was completely shot. Replaced, and the problem is gone. Also took this opportunity to replace the transmission mounts, after 31 years and 106K miles, they were definitely very tired.