Does this sound like A/C Compressor clutch?

9

92Pony

New member
My son pulled in in his '98 (3.4l) last night, and I noticed a lot of 'noise' coming from the engine compartment. We swapped the A/C idler pulley several weeks back thinking it was making noise (and upon inspection after removal, the bearing in it was indeed toast). It helped, but last night I noticed engine noise seems more pronounced than it has been recently.

We popped the hood to nose around. I had him reach in and turn ON the A/C. As soon as the clutch engaged, the noise went away. Turned off the A/C (allowing the clutch to freewheel) and it sounds like a barrel full of rocks rolling down a hill (not THAT bad, but you get the idea ;-) ).

Does that sound like the clutch (or perhaps more specifically it's bearing)?

I've done some searching on here and a lot of others seemingly get noise when they turn their A/C on, but this is opposite.


TIA
 
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Well, instead of asking the internet for opinions, I'd get a $5 mechanic's stethoscope from Harbor Freight and apply it to the front of the clutch when the A/C is off. Should be pretty obvious. Everyone should have one.

http://www.harborfreight.com/mechanics-stethoscope-69913.html

But given that idler is new I can't think what else it would be unless maybe belt is really chewed up, but that's a major long shot.
 
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TheDurk said:
Well, instead of asking the internet for opinions, I'd get a $5 mechanic's stethoscope from Harbor Freight and apply it to the front of the clutch when the A/C is off. Should be pretty obvious. Everyone should have one.

Mechanic's Stethoscope

But given that idler is new I can't think what else it would be unless maybe belt is really chewed up, but that's a major long shot.
Click to expand...

Thanks Durk. Sounds like a great addition to my tool collection. When I worked at a Chevron gas station in the 80's, I remember seeing a mechanic use a long 3/8" or 1/2" extension putting one end on the suspected bad part and the other next to his ear to figure out if it was the culprit making the noise. I think the stethoscope is definitely a step up from this old school method though.
 
TheDurk said:
Well, instead of asking the internet for opinions, I'd get a $5 mechanic's stethoscope from Harbor Freight and apply it to the front of the clutch when the A/C is off. Should be pretty obvious. Everyone should have one.

Mechanic's Stethoscope

But given that idler is new I can't think what else it would be unless maybe belt is really chewed up, but that's a major long shot.
Click to expand...


Not discounting the value of the tool you recommended, but dang, isn't that sort of the point of car forums??
 
92Pony said:
Not discounting the value of the tool you recommended, but dang, isn't that sort of the point of car forums??
Click to expand...

TheDurk helps ALOT of people on here. A major contributor in a mostly positive way. His advice was sound. Diagnosing noise on internet car forums is tough. I suggest either doing what he said or upload a sound byte to let us listen to.
 
Could be the compressor pulley bearing. Stethoscope makes life easy, if you don't want to go that way, remove the belt and spin the pulley by hand. If it makes even a little bit of noise, you need to replace the bearing.

Here is the bearing number: 30BGS10DST2 Nachi

OEM bearing runs about $50. A guy in FL sells these bearings (aftermarket) for $22 shipped on eBay. I bought one and works good so far.
 
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92Pony said:
My son pulled in in his '98 (3.4l) last night, and I noticed a lot of 'noise' coming from the engine compartment. We swapped the A/C idler pulley several weeks back thinking it was making noise (and upon inspection after removal, the bearing in it was indeed toast). It helped, but last night I noticed engine noise seems more pronounced than it has been recently.

We popped the hood to nose around. I had him reach in and turn ON the A/C. As soon as the clutch engaged, the noise went away. Turned off the A/C (allowing the clutch to freewheel) and it sounds like a barrel full of rocks rolling down a hill (not THAT bad, but you get the idea ;-) ).

Does that sound like the clutch (or perhaps more specifically it's bearing)?

I've done some searching on here and a lot of others seemingly get noise when they turn their A/C on, but this is opposite.


TIA
Click to expand...

I had a noise in my 98 limited that was driving me insane. It sounded like a pulley was rattling, and only manifested itself after the engine was warm. Cold engine = silent (once the fan quit howling).

I replace the a/c idler pulley, then just took the a/c belt off. I replaced the alternator, PS pump (needed it anyway) and false water pump. No go. Actual water pump was replaced about 10k prior to me buying it, so imagine my surprise when I popped the front [plastic] cover and found it somewhat difficult to turn by hand with the timing belt off.

So I thought, ah hah! this is it! And I replaced it with an OEM pump from Rock Auto or some such place, and...

THE NOISE RETURNED when the car got warm. I about put a bullet in the thing right then and there. Infuriated, I ordered every single rotating thing on the front half of the engine that I hadn't already replaced or ruled out by removing the belt and replaced them one by one the following weekend until I found the culprit.

Long story short, it was the timing belt idler pulley that sits in the "V" of the belt right under the water hose outlet.

When I relayed this story to my friend who is a 20 year professional, ASE certified auto tech (to my 20-odd years of amateur wrenching), he laughed hysterically and asked why I didn't just use a mechanic's stethoscope to begin with. I looked at him dumbfounded as to why I didn't think of that sooner.

So, moral of the story: there are a crap-ton of things that could cause that noise. Try to narrow it down before being a moron like I was.

But hey if you insist on letting us help - try taking a video of the sound and posting it on the youtubes.
 
nissanh said:
Could be the compressor pulley bearing. Stethoscope makes life easy, if you don't want to go that way, remove the belt and spin the pulley by hand. If it makes even a little bit of noise, you need to replace the bearing.

Here is the bearing number: 30BGS10DST2 Nachi

OEM bearing runs about $50. A guy in FL sells these bearings (aftermarket) for $22 shipped on eBay. I bought one and works good so far.
Click to expand...

Thanks for the info nissanh!!


I'll try and get a video of it in action and post it up.
 
mckennar said:
I had a noise in my 98 limited that was driving me insane. It sounded like a pulley was rattling, and only manifested itself after the engine was warm. Cold engine = silent (once the fan quit howling).

I replace the a/c idler pulley, then just took the a/c belt off. I replaced the alternator, PS pump (needed it anyway) and false water pump. No go. Actual water pump was replaced about 10k prior to me buying it, so imagine my surprise when I popped the front [plastic] cover and found it somewhat difficult to turn by hand with the timing belt off.

So I thought, ah hah! this is it! And I replaced it with an OEM pump from Rock Auto or some such place, and...

THE NOISE RETURNED when the car got warm. I about put a bullet in the thing right then and there. Infuriated, I ordered every single rotating thing on the front half of the engine that I hadn't already replaced or ruled out by removing the belt and replaced them one by one the following weekend until I found the culprit.

Long story short, it was the timing belt idler pulley that sits in the "V" of the belt right under the water hose outlet.

When I relayed this story to my friend who is a 20 year professional, ASE certified auto tech (to my 20-odd years of amateur wrenching), he laughed hysterically and asked why I didn't just use a mechanic's stethoscope to begin with. I looked at him dumbfounded as to why I didn't think of that sooner.

So, moral of the story: there are a crap-ton of things that could cause that noise. Try to narrow it down before being a moron like I was.

But hey if you insist on letting us help - try taking a video of the sound and posting it on the youtubes.
Click to expand...


I think I'm going to do this. I'm having the EXACT SAME problem with the same symptoms/noise and it's driving me up the wall. Sounds almost like when driving with bad tires. A rythmic 'thumping/rolling' noise (not knocking) that only manifests itself at idle once warm. I can tell it's from the front bottom, and it seems to be more pronounced with AC on, so I was thinking AC idler.

Question, as I've never done a timing belt yet: if it does happen to be the idler pulley for the t-belt, would it be bad to let sit until the next change? The T-belt was done at 88k before I bought it, and it's currently at 150k. I'll do it on schedule in the next 30k, but that's about a year and a half from now.
 
Did anyone ever figure this out or have an answer. This is exactly what mine does. No noise when the ac is on and compressor is engaged. Once the compressor is off/disengaged its noisy. I replaced the AC idler puller today and its doing the same thing
 
For me (OP), it indeed ended up being the compressor clutch. After considering parts pricing, labor pricing and warranty coverage, we opted for a shop to replace the compressor.
 
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