markzeronine

I've been noticing on these hot summer days with the ac on, sometimes (maybe one in 10 shifts) there's a kind of growl or pump noise between first and second gear shifts. Sometimes happens between 2 and 3, I think it has more to do with the clutch being pressed in and not the actual shifting of gears. I can only get it to make the noise when the ac is on, any ideas on what it could be? Car is a low mileage 06 z06. Also makes a similar or maybe the same sound when starting cold which I'm not sure if it's related or not. https://www.youtube.com/watch?v=MR_6ydmNKZc&feature=youtube_gdat a_player

RicK T

Even with low mileage it could be the throwout bearing, which you would hear when pushing the clutch pedal down and it engages the clutch fingers.

I have to ask a basic question though, how is the clutch fluid? Do you change it frequently or even regularly? What color is it? Is the level low? We need to know this basic stuff before going any further.

markzeronine

I just did the fluid yesterday for the first time. Luckily it wasn't too dirty. It started doing this a little before I did the reservoir cleaning though. I just tried it about 5 mins ago and I can actually do it with the car in neutral never touching the clutch so it's not the pedal itself or any of the clutch mechanism as far as I can tell. Again it will only do it with the ac on. Ac off it will not do it at all. I've also learned "how to" make it do it all the time with the ac on. Floor it quickly and let off rapidly. As the rpms come down to around 2000 rpm it sounds almost like a groan or gasp for air. Then it goes away. I took a video, you'll have to have your volume up pretty loud to hear. What in the ac system could make this noise?

markzeronine

https://www.youtube.com/watch?v=m1ZetGbITaQ&feature=youtube_gdat a_player

RicK T

Okay, so it could the the A/C compressor, water pump, belt tensioner/idler or alternator. Gonna need to get in the engine compartment and try to isolate it. No other way I can think of to do it.

markzeronine

I was thinking the same. Any advice on how to start trying to isolate it? I was thinking turning the ac on and off would narrow it down to the ac belt, and compressor but maybe not? There's a little slack on that belt (maybe more than normal, not positive) is it self adjusting or is there a tensioner on that? The car came with an aftermarket warranty that expires in November I believe. I've never used it but it may be a good time to try it out, I just really don't like other peoples hands on my car and/or it being out of my sight.

RicK T

Frankly I don't know for sure about the LS7 serpentine belt setup. If it's the same or similar to the LS2/3 then the A/C has it's own belt and tensioner, mounted down low.

I have read where some people have removed the A/C belt to assist with diagnosing noises. I imagine it's not easy though.

Be patient, I'm sure guys who have dealt with this kind of thing will chime in over the next day or so and will offer good advice.

BJ67

The a/c belt is separate on the LS7, very easy to remove when you jack up the front and slide under the car. Just slide off the outer serp belt first

markzeronine

The thing is, even if I take off the belt I'm sure it's going to be the same as when I have the ac turned off. When the ac is off it will not make the sound at all. If there is no belt it will be the same thing as the ac not running so there should be no sound right?

I guess I could take the main serpentine belt off while leaving the ac belt on, turn the ac on and do the same revving process. If it still makes the sound then, it should completely isolate the problem to the ac belt, compressor or tensioner.

RicK T

Yea, same idea, different things get eliminated. If you're going under the car to remove either belt, you could try turning the A/C tensioner by hand to see if you can detect any roughness. I'm just thinking maybe it only acts up when the A/C is on and dragging. Just gotta try stuff.

markzeronine

Yeah first thing I'll do next weekend is get someone to rev the car while I check under the hood, maybe get one of those stethoscope type of things to put me in the right area. I wonder how hard it is to get to belts on these things. After a quick look it doesn't seem like there's a whole lot of room but it can't be too bad.

V4kerker

markzeronline you can check the AC belt and tensioner from the top. Is the car's AC putting out cold air?

This summer I found that my AC belt had jumped off the tensioner and the belt flipped inside out. Couldn't believe I didn't tear something up. I never had any strange noises though. I got the belt flipped around normal and back on the pulleys and tensioners and all is good now.

This may not be your problem but I've heard that cars can through a belt sometimes.

markzeronine

Thanks for the input. Ac is ice cold and the belt seems like it's on the right way

vette6500

Mine did the moaning noise when clutching with a/c on for a year or two before it gave up the ghost. No more cold air since, been over 2 years without a/c.
Thankfully I got a small daily driver and use the C6 only for autocross or on weekend when I don't mind wetting my shirt or during colder months.

Too scared to find out how much it'll cost to fix whatever is broken, lol. I'll take it to pepboys one of these days to at least have them diagnose the problem in case it's a cheap fix...

markzeronine

It's definitely the ac compressor or compressor clutch, excuse my lack of technical understanding of the ac system but pinpointed it to that system for sure. Time to find out how this aftermarket warranty works