A/C system is popping when truck is started or A/C is turned on.

[Heath]

I have a 2004 GMC Sierra 5.3 Crew Cab and I have had A Popping sound coming from either under the hood or in dash. It's apparently a release that's not happening and pressure is building and releasing at once when I start the motor with AC on or just turning it on while driving. Just wanted to see if anyone has had this problem and see what the cause may be. Also I am losing Freon over several weeks as well and I have read where some mechanics DO NOT recommend using any stop leak products in the system because it will cause other parts to gum up. Any thoughts on this as well? 

Thanks for any input you may have for me!!

+

Heath 

 

[richard wysong]

If you plan on keeping the truck DO NOT use stop leak, if you ever have to open the system the stuff solidifies when exposed to air. Common leak would be compressor seals. If the popping noise is under the dash it's probably one of the blend door actuators with a stripped gear. Stop leak will not stop a leak at the compressor shaft seal

Edited June 19, 2025 by richard wysong

[Heath]

I have read not to use stop leak and saw some mechanics video saying do not use the products.

The popping sound is more along the lines of the sound of the old carburetors popping sound way back when. I had all the blendors replaced last year and I am familiar with the popping sound they make. 'the sound comes from under the hood I am almost positive.

Thanks

Heath

[richard wysong]

I would take a look at the compressor clutch and the belt and tensioner, there isn't much in the a/c system that can make a popping noise. It's hard to see so you may have to jack it up and slide underneath while a helper starts and turns the a/c on. Make sure you use jack stands. 

[Heath]

I recharged the ac system and so far the popping has subsided. We shall see in the  coming days if being low of Freon was causing this sound.