Low RPM Rattle from front of engine
 

I have a 1990 S2.. 130K miles. about 2 weeks ago I noticed a rattle noise coming from the driver side up front. At first I thought it could be an exhaust rattle. Now after 2 weeks of guessing I have narrowed it down to the alternator area.. I put a long screw driver on the alternator and lowered my ear right on it and it is def coming from that, but when I speed the engine up the noise goes away. If it was the bearing, I would think that noise would increase. Maybe there is a belt tensioner going bad? Also, this is weird, just today I noticed with the head lights up, the rattle noise increased twice as much. One more thing and Im done explaining.. on 2 occasions I drove it approx 2 miles and driving from a stop light, I got a screeching belt noise for a few seconds. Hopefully, there is someone on here that has had the same scenario

Did you hear the screeching sound when the AC was just turned on or when the compressor engages?
That is when I tighten the AC/Alt belt 1/2 turn.

The rattle could be the AC compressor clutch also.

J_AZ

Might have a loose bolt on the alternator, when the power draw is high there is a lot of load being put on the drive belt which could wiggle the alt in place if not locked down.

What V2 said.....
Seriously...
2 days ago I heard the same rattle.
Yesterday I had a squeal
While checking alternator belt for tension I noticed that the bolt was backed out most of it length. (foward actually).
Loosened tension, pushed bolt back in, re tensioned and tightened bolt. Then put "torque seal" on the bolt head for future visual reference.
No more rattle or squeal.
No compressor installed, just the alternator.


'87 944 NA
I've been lurking for 6 months. Had to reply to this one.

https://picasaweb.google.com/100895552205203987813/April222014#6005315907319060178

My 86 NA does the same thing, havent bothered to fix it yet but it is annoying.

A common cause of this rattle is loose or broken AC compressor mount bolts. This is caused from belt adjustment and not loosening the 2 AC mount bolts. This happenned to our 89 NA twice. Good luck.

Oh yea, I had my compressor off a while ago and the bolts weren't all the way tight...drove 150 miles and heard an awful noise, tightened the compressor hangers down and it was gone

Thks everyone... I will remove the belt and check around the compressor. The belt was squeaking this morning till it caught... I can always count on good info on this forum!

I just needed to tighten the a/c belt.. these cars are engineered so different... but Im learning...The vibration and rattle was the compressor jumping back and forth till it got a faster rpm and then it evened out... a little embarrased here, but this car is all new to me.