Rattling noise at idle. Coming from front of motor. Help!

B

BuickMike

Money pit
Joined
Jun 7, 2001
I have this nasty rattling sound that is coming from the front of the motor and only happens at idle. It almost sounds like rocks. It's driving me nuts! I thought it was the alternator because it had noisy bearings when spinning it with my hand, but I replaced that and the noise is still there. :mad: I also spun my AC compressor when disengaged as well as the idler pulley and they seem fine. Since my AC needs recharging I can't engage the AC and see if that makes a difference. I'm hoping it's not anything serious. Would anything internal make this noise, or am I not looking hard enough?
 
i had the same promblem

check the bracket that bolts on the A/C compressor to the block,there are 2 bolts on mine that backed completely out.You'll need to remove the alternator and A/C compressor to get to the bolts
 
Man, I hope that's it. If I stand over on the drivers side of the car it sounds like it's coming from the AC compressor. Even the metal lines off of the compressor vibrate in conjunction with the rattle. But then there is no problem with the compressor pulley and the thing is not even engaged. That's why I thought it was the alternator. Is there any way to at least look at them without removing everything? I'll check after work tomorrow.
 
Could be the waste gate rod being to lose, or maybe the gate sticking, that's what I had
 
I have bad bearings in my alternator making that same noise, sounds like a weird knocking noise...
 
sounds exactly like mine,only rattling while sitting at idle.I took the time to pressue wash the front of the engine and paint the alternator and brackets while I had them off already,just another suggestion,of course if this isn't your problem you may not be in any mood to paint parts!:eek:
 
Thanks for all the replies. Last night I swapped the alternator out and therefore the drivers side IC brackets are tight for sure. From the drivers side it sounds like the noise is coming from inside the AC compressor, but ut's not engaged. Right now I'm really thinking it is the bracket holding the compressor to the block.

I'll pull the belt and see what happens, but I doubt I can replicate it that way since the noise only happens at one RPM and it will probably idle a little higher with the belt off.
 
Should idle the same, its determined by your chip, not load. I had a problem similar to yours, but found my belt of unknown age had stretched a little, and the tensioner was kinda bouncing around. I put a new belt on and it went away.
 
Well, I took the AC Compressor off and found out that the bracket that needforspeed mentioned had loose bolts. I tightened them up and the rattle is completely gone! :)

Thanks for all the replies.
 
Mine makes a similar, marble bouncing type sound at idle when the motor is cold. Then once it warms up, it goes away. Could this be the same issue?

To me it sounds like the tensioner. I put the 63.5" inch belt on the car recently, so it cant be "bouncing around" or anything. None of the pulleys make any noise.

Any suggestions for me?
 
smaller belt??

do you have a part #(or source) for a smaller belt

i replaced mine with a stock # when i got the car but found that theres only little tension (belt is bouncing at idle most likely slipping on launches ) appears tensioner is at its travel limit
a slightly smaller belt would definitely help
I will look into compressor mtg brkt since I also have similar ocassional knock at idle . would be nice if its just the belt .sounds like a shot alternator but its brand new , waiting on parts (Timing chain /oil pump/water pump) and will do them due to mileage , if noise continues after that guess ill tear it down
would like to eliminate the belt problem first since it would still be loose after timing chain get redone
 
Originally posted by GrndNatnl
Mine makes a similar, marble bouncing type sound at idle when the motor is cold. Then once it warms up, it goes away. Could this be the same issue?
Click to expand...

Hard to explain why it would go away when the car warms up. Try using a length of radiator hose held to your ear to isolate the sound or a mechanic's stethoscope if you have one around.

Have you inspected your oil for metal shavings recently? That's also a simple check.

-Scott
 
My noise happened cold or hot. My alternator also had noisy bearings, so I replaed it as well. Now I can actually hear the injectors fire. :)
 
AC noise

There is a bearing in the AC clutch that is operation when the AC is not in use and the clutch is free wheeling. Take off the AC fan belt and see if the noise goes away. Does your AC work OK and cool down OK?
 
Ok.. I'll check these things whenever I get a chance, and report back. I need to get a stethoscope somewhere. All the tools we have at home and no mechanics stethoscope! I usually use a long screwdriver.

Havent fooled with the A/C since summer time, but I notice if I have the defroster set when cold idling, it engages and disengages over and over again. It's always done that. The compressor is most likely the original.

Oil has been fine. No metal or anything.


Pacecarta: Goodyear Gatorback drive belt #: K060635. AutoZone can get them. Cost me $25 bucks. They list the 63.5" belt in their system under our car anyway.
 
thanks for the heads up on the belt# and source
I went through autozone online for the timing set/waterpump/HVoil pump kit and gaskets (they are in transit already) and never thought to check for belt , ill have to get one
 
I had a problem with the rattle at the front of the engine a couple of years ago. It drove me nuts until I figured out it was the tensioner rattling. I had bought a new belt at a parts store. They looked it up in their book and sold what it listed. It was too long by maybe a 1/4". The stock GM belt is 1618 mm long. Thats about 63.7 inches. I bought a new one from the dealer and the problem went away. You may be lucky enough to get a belt at a parts store that works, but I will only buy one from the dealer from now on. I couldn't find a parts store that had belts in mm. Only sold them in 1/2 inch increments. It should be 63.75 inches and around here only the dealer had the right size. You wouldn't think 1/4" would make that much difference, but it did for me. Go figure.
 
gatorback belt 63.5

checked out auto zone site last night and ordered the goodyear gatorback belt #4060635 $24.99 + 1.50NJtax ,free ship 3-5 days , cant get it from autozone stores , online only!
they also listed a cheaper kelly around $12.00 with similar part # K60635 that should also have done the trick
 
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