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2000 Chevy Tahoe a/c noises
07-28-2011, 11:48 PM
Post: #1
2000 Chevy Tahoe a/c noises
I have a 2000 Tahoe that makes a noise while accelerating with the air conditioning on. The noise sounds like the cooling fan striking the plastic shroud surrounding the fan. The noise persists until I let off the gas. If I accelerate slowly, there is no noise. I did have some wooble in the cooling fan and replaced the water pump and cooling fan clutch assembly. However the noise continues. I have also replaced my tension pulley for the serpentine belt. Could this be my a/c compressor going bad, as I still get ice cold air. HELP
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07-29-2011, 05:58 AM
Post: #2
RE: 2000 Chevy Tahoe a/c noises
You might want to check the motor mounts to make sure that they aren't letting the motor move to much under a load. I usually open the hood, hold my foot on the brake, put it in gear, and give it a little gas. Let off the gas, go to reverse, and give it a little gas. You can usually peek under the hood and watch how much the motor moves. Excessive movement usually means a worn or broken mount.

Please let us know what you find.

Thanks for using the forum,
Garner

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07-29-2011, 09:48 AM
Post: #3
RE: 2000 Chevy Tahoe a/c noises
(07-29-2011 05:58 AM)Garner Wrote:  You might want to check the motor mounts to make sure that they aren't letting the motor move to much under a load. I usually open the hood, hold my foot on the brake, put it in gear, and give it a little gas. Let off the gas, go to reverse, and give it a little gas. You can usually peek under the hood and watch how much the motor moves. Excessive movement usually means a worn or broken mount.

Please let us know what you find.

I will check it in the next few days, and will let you know the results. Thnx
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06-21-2014, 03:09 AM
Post: #4
RE: 2000 Chevy Tahoe a/c noises
(07-29-2011 09:48 AM)Darin Wrote:  
(07-29-2011 05:58 AM)Garner Wrote:  You might want to check the motor mounts to make sure that they aren't letting the motor move to much under a load. I usually open the hood, hold my foot on the brake, put it in gear, and give it a little gas. Let off the gas, go to reverse, and give it a little gas. You can usually peek under the hood and watch how much the motor moves. Excessive movement usually means a worn or broken mount.

Please let us know what you find.

I will check it in the next few days, and will let you know the results. Thnx

Hey guys, I am having the exact same problem, 2000 Chevy Tahoe 5.3 liter. I checked motor mounts as advised above and my mounts are rock solid. There is no wear on the fan or shroud at all, so I am stumped as to what the problem is.

A good friend of mine suggested that it might be the ABS system. This issue is usually within the first 10 minutes of starting the truck. I took my truck out tonight and drove a back road with my foot resting on the brake pedal. The noise happened as predicted when I accelerated and I felt absolutely nothing through the brake pedal.

Any advice would be most helpful
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06-21-2014, 09:12 AM
Post: #5
RE: 2000 Chevy Tahoe a/c noises
This is the point where somebody there has to figure out exactly what the noise is. If it is the ABS motor the likely cause is rust built up under the front Wheel Speed Sensors. (WSS) There is a service bulletin from GM about this problem. I usually get the front end off the ground and properly support it. Check the wheel bearings. A loose bearing can cause ABS problems. If the bearings are OK, remove the tires & turn the wheels to one side. You can remove the attaching bolt and lift the sensor but it usually won’t come up past the backing plate. Using sandpaper, a small chisel, & possibly a magnet to keep rust from going down the hole, clean all of the corrosion away from the WSS mounting hole. Apply some Anti-seize or Dielectric grease & re-install the WSS. Do the other side the same way, properly torque the lug nuts, & you should be good for some time. This is a very common problem if you live in a region where they use salt to melt snow off the roads.

Please let us know what you find. Your experience could help someone else.

Thanks for using the forum,
Garner

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06-21-2014, 11:05 AM
Post: #6
RE: 2000 Chevy Tahoe a/c noises
Garner makes a good point about finding the cause first, as in any diagnosis, but let's narrow down the problem before we jump all over the place.

ABS issues will only come up during braking and if you want to isolate that just pull the big fuse for the ABS system. Yes, the dash light will come on (and it will probably set a code) but you will know it's NOT the ABS if the noise is still there.

You can also pull the clutch wire on the AC compressor to isolate that. Operate everything as normal (blower and selector positions) and if after the usual time the noise isn't there you have it nailed. The typical noise from an aging AC compressor sounds like a coffee can full of marbles rolling across the floor. It's VERY common and does not mean the unit will fail right away. (unless it gets louder in a hurry)

BTW, if it turns out to be an ABS issue you may be able to have someone read the codes, although weak sensor signals don't always set a code. The situation Garner laid out for rust under the sensor creating more distance generally gives you a problem at slow speed while applying the brakes.... say 20 mph and under. The codes available for ABS fall into only a few categories. The ABS motor itself, the motor relay board, (both of these are major $$) and the wheel sensors themselves. In the case of the front wheels it would be 50/50 as to needing just a sensor or the entire hub / bearing, which will be the sensor AND the wheel bearing. Each complete side is $200 - $300 (aftermarket) so obviously you want to avoid buying them if not needed.
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06-21-2014, 11:47 AM
Post: #7
RE: 2000 Chevy Tahoe a/c noises
Thank you for the responses. I suppose I should have given a bit more on the drive I took last night, and the conditions that I live in. I live in Northern California, and while I live in snow country using salt is rare (I think they outlawed that some time ago). The undercarriage of my Tahoe is cleaner than most, I know what the high alkaline dirt can do up here.
I tested the 'rattle' last night on a cold motor, I got her up to about 45 and accelerated hard and sure enough the noise started as soon as I started accelerating. The next stop sign I repeated right off the line and the noise responded like Pavlov's dog. By the time I turned around and headed home the engine was warm and the noise would not happen.
Failure on my part - I did not check to see if the noise would happen with the ac off.............
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06-21-2014, 12:16 PM
Post: #8
RE: 2000 Chevy Tahoe a/c noises
The compressor also runs in the defrost mode so make sure it's OFF or pull the wire just to be certain.
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06-21-2014, 02:46 PM
Post: #9
RE: 2000 Chevy Tahoe a/c noises
Update -
I drove to the store this morning with the ac off, and absolutely no rattle. I spent about an hour in the store, came back out and drove home with the ac on. As I expected, the rattle was back every time I accelerated hard. Easy acceleration the noise does not happen.
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06-21-2014, 11:18 PM (This post was last modified: 06-21-2014 11:19 PM by Rupe.)
Post: #10
RE: 2000 Chevy Tahoe a/c noises
Ya might want to observe things with the hood up and watch the drive belt. What I am thinking is the compressor noise might change with engine speed but should not differ substantially with the rate of speed change UNLESS the belt is slipping (worn) or the tensioner is hanging up, (causing belt slip) in which case you might duplicate the noise by jazzing the throttle with your hand while watching and listening. Also consider that if you accelerate hard the trans will shift down, which may be similar to juicing the gas by hand. IOW, not so much the hard throttle but the sudden change of engine speed by a downshift.

As a side note, if the belt is several years old or has been on there for more that 30k miles you might try changing it "just because" and checking the pullies while in there. I run a small fleet and I find the Good Year belts last WAY longer than the Gates or others. (at least 50K miles) I also use Good Year pullies when I hear a bad bearing at belt change. Not trying to sell you... just going from 40 years in the business and about 20 years of that in fleet service.
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