1990 chevy C1500 2wd Rattle ac on 4.3 eng


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1990 chevy C1500 2wd Rattle ac on 4.3 eng

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toolman1000
New User

Sep 9, 2009, 10:07 AM

Post #1 of 3 (4163 views)

1990 chevy C1500 2wd Rattle ac on 4.3 eng	Sign In

there is a rattle at idle with engine hot or cold when I turn on the ac this truck has one serpentine belt which runs ac,water pump . power steering ,idler pulley , tension pulley, and crank shaft. the rattle is all but gone when I come 100-200 R.p.m.s off idle.
I thought the compressor was bad, so I installed a used one TWICE !! same problem.
so I bought a new/reman. unit also changed the orifice tube, and receiver dryer
flushed system added new oil for R134A and weighed in charge after pulling system down to 500 microns of vac. all 4 compressors cooled beautiful no problems other than this Rattle I have changed the belt and both idler pulleys power steering is quiet when stethscope is used as is the water pump .
could the load from ac cause something in engine to make this rattle !!!???????

engine runs great , auto transmission shifts well , uses no oil I even checked the cat.converter=ok odometer broken guessing close to 100,000 miles

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 9, 2009, 10:21 AM

Post #2 of 3 (4157 views)

Re: 1990 chevy C1500 2wd Rattle ac on 4.3 eng	Sign In

Gees! Get a stethoscope and fix the bearing causing the problem and quit throwing parts at it!

T

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 9, 2009, 10:24 AM

Post #3 of 3 (4154 views)

Re: 1990 chevy C1500 2wd Rattle ac on 4.3 eng	Sign In

The noise most likely has nothing at all to do with the A/C. The fact that the compressor is pumping causes a jerking action to the belt and that's what brings out the noise.

There are a couple of things to look at

Torque converter bolts........ make sure they are tight and try to look up at the flywheel/flexplate for any cracks that would show up as rusty spots.
Harmonic balancer....... make a mark on both the inside and the outside that align with each other and run the engine. shut it off and see if the marks still align.
The belt itself.......... I have run into time when the belt is just a little too long and it causes the tensioner to hit against it's stop. Once the compressor starts pumping, it will just rattle against it's own stop.

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