Help Diagnosing Screaching/crackling Noise

alvocado · August 7, 2007

For the past week, my '02 Yukon Denali has been making a really strange noise. My wife described it as the sound you would hear if you were dragging branches under the truck while moving (sounds rediculous but after driving it, I see how she would think that.) It occurs while accelerating and I think it may only occur when the A/C is on. The A/C is still blowing cold but I could not reproduce the issue while running with the A/C and cabin fan off. I thought the sound was similar to a starter motor screaching/crackling but it never happens while starting the car, only while accelerating. It's definitely coming from the engine bay vs. suspension. I've also noticed the idle is quite a bit rougher with the A/C running and much rougher than the typical load you would experience with the A/C on, however it goes to normal after turning the A/C off.

I know this is a bit generic but I'm having a hard time pinpointing it while driving. Could this be an A/C compressor going bad? My first thought was something on the belt since it seems to be tied to engine RPM. Any ideas on where to look would be appreciated. Thanks.

alvocado · August 7, 2007

For the past week, my '02 Yukon Denali has been making a really strange noise. My wife described it as the sound you would hear if you were dragging branches under the truck while moving (sounds rediculous but after driving it, I see how she would think that.) It occurs while accelerating and I think it may only occur when the A/C is on. The A/C is still blowing cold but I could not reproduce the issue while running with the A/C and cabin fan off. I thought the sound was similar to a starter motor screaching/crackling but it never happens while starting the car, only while accelerating. It's definitely coming from the engine bay vs. suspension. I've also noticed the idle is quite a bit rougher with the A/C running and much rougher than the typical load you would experience with the A/C on, however it goes to normal after turning the A/C off.

I know this is a bit generic but I'm having a hard time pinpointing it while driving. Could this be an A/C compressor going bad? My first thought was something on the belt since it seems to be tied to engine RPM. Any ideas on where to look would be appreciated. Thanks.

I did some more diagnosing this evening. There is an audible ticking noise present which under acceleration, could be he source of the issue. Is it possible that a bad valve or lifter could be the cause. It was difficult to reproduce the sound but it did occur while I had the RPMs around 1500 using a broom handle and standing outside the car. The source did not seem to be coming from the belt accessories as previously thought but it was hard to tell from standing by the drivers door.

alvocado · August 8, 2007

Problem identified: it's the A/C compressor and likely related to the TSB posted on the forum: http://www.gm-trucks.com/forums/index.php?showtopic=41863. I didn't find that on my first search since it was related to the tensioner. Thanks to orangeman91 for the autoaironline.com referral. I just ordered everything I need for $376 shipped vs. $700 from the dealer.