Hello CarTalk!
Just a quick question.
I drive a 1995 Chevrolet Siverado 4x4 with the 5.7 Liter V8 engine. So far the truck has been excellent and only has around 74,000 miles. I’ve done my best to follow up on all repairs and preventative work to keep it running nice and strong.
Recently, I’ve noticed that whenever I turn off my truck (with the A/C already off) there is a hissing sound coming from the engine, and during start up and running the truck’s A/C makes a grinding sound whilst running.
I’ve popped the hood and the compressor does indeed make a strong, grinding sound, as if sand was inside of the berings.
We’ve gone to the local auto-parts store and purchased oil and additional coolent and found no effect.
My father believes it’s just the compressor’s age that causes the noise, something that wouldn’t suprise me. However, I just wanted to be sure. I was planning on taking the truck to a Chevy dealer anyway to have them give it a once over to make sure everything was alright and thought this A/C issue would give me the reasoning to do so.
I hardly use my A/C but it is a luxury that I don’t think that I could live without on those hot days.
Thanks! Any advice would be wonderful!
First of all if a user named STAR882 responds you need to be aware that he is giving out false and misleading information about automotive A/C.
Next… do not bring your truck into the dealer for service unless you like paying higher prices for service. Find a independent shop that specializes in A/C and have them look at it.
As far as your problems you are encountering. The hissing noise could be normal. It could be the pressures in the system equalizing after the A/C is shut off.
You could have a compressor clutch bearing that is making the grinding noise or the clutch drive plate itself is coming apart. In either case it doesn’t require replacing the compressor if that is the problem. The clutch assembly can replaced on the vehicle and without opening the system up.
Hi,
The hissing sound you hear after you shut off the engine is the freon (R134a) moving from the high pressure to the low pressure side of the system. This hissing lasts about 20 to 40 seconds. I hear the hissing on my 1993 Caprice and 2000 Blazer.
When I got the 1993 Caprice in 2002 it still had the original serpentine belt. When I started it and turned on the AC, the compressor was very noisy. I thought I needed new compressor clutch at the least. I replaced the serpentine belt and the compressor was quiet after that. If the serpentine belt is 3 or 4 years old on your truck, replace it and see if the compressor quiets down. I’ve have good luck with Goodyear Poly-V belts. I ordered my last set at a reasonable price from Advance Auto.
Good luck,
Ed B.
What oil and “coolant” did you add? For R134a, the oil should be polyol ester oil. And there should be no reason to add more oil and refrigerant unless there is a leak. If there’s too much oil, it can “oil log” the compressor and cause it to fail. (Granted, it would take a lot of oil for that to happen but it certainly can happen!)
Is either the evaporator coil or condenser coil dirty? A dirty evaporator coil can cause liquid slugging and a dirty condenser coil can cause excessive pressure, both of which can cause compressor damage.
Get estimates from several good shops. A failing compressor might just have to be replaced but you might be lucky and something cheaper could be done. (Can you verify that it’s the compressor? Maybe the condenser fan motor has a worn bearing.)
You’re strongly urged to follow Willey’s advice; from first sentence to last. 