R4 A/C compressor noise

[plpeyton]

I'm having a very similar issue with a brand new Murray R4 compressor I put on my 73' GMC. The compressor is a 1991 year model, and it's making the same racket as the rebuilt unit I just replaced. I have to wonder if these particular compressors aren't just naturally loud. The original R4 I built the system with I replaced with the NEW Murray unit along with flushing the evaporator, some of the hoses and replacing other hoses. I also replaced the condenser and pulled a full vacuum on the system and refilling with R-134a (about 5 cans) and somewhere between 8-10 ounces of 150 PAG oil. There really aren't any factory specs for what I've done here, so I don't have factory capacity guidelines to go by. What I have done though is look up R-134a refrigerant pressure charts, and filled to what the recommended low side pressure should be in correspondence to the ambient air temperature. The system cools really well (I have vent temps between 38 and 50 degrees, depending on whether or not the truck is MOVING) but it does make a ton of noise, just like in the above video. Any experiences people have had with these particular types of GM A/C systems is greatly appreciated.

 

[plpeyton]

The original R4 on my '90 sounded about that loud its whole life. lasted until 2013.

Interesting. I have a brand new 91 R4 compressor making the same exact racket in the video. Hard to tell if it's been damaged or not. Gets louder with low refrigerant.

 

[Schurkey]

What was the original R12 capacity of the '73 GMC? 5 cans of R134a seems...enormous. But then, I'm not familiar with conversions.

Is that 8--10 ounces of oil PLUS the stuff the compressor came with, or did you drain the compressor?

What is your high-side pressure?

 

[plpeyton]

What was the original R12 capacity of the '73 GMC? 5 cans of R134a seems...enormous. But then, I'm not familiar with conversions.

Is that 8--10 ounces of oil PLUS the stuff the compressor came with, or did you drain the compressor?

What is your high-side pressure?

The original 73 called for 52oz of r12 and 10 ounces of mineral oil. Later on, gm reduced those amounts to 8oz of mineral oil and 48 oz of r12. Not sure on the high side reading. Have an aftermarket 16x26" condenser

 

[Schurkey]

Trying to do A/C work without using a set of manifold gauges?

 

[plpeyton]

Trying to do A/C work without using a set of manifold gauges?

I filled it with a set of gauges. High side readings can be tricky. I couldn't open the high side valve for safety reasons and the guage set wouldn't let me get a reading without doing just that.

 

[Schurkey]

I filled it with a set of gauges. High side readings can be tricky. I couldn't open the high side valve for safety reasons and the guage set wouldn't let me get a reading without doing just that.

I have no idea what "safety reasons" you're talking about.

Time to re-connect the gauge set, and find out if the high-side is so high it's damaging the compressor.

 

[plpeyton]

I have no idea what "safety reasons" you're talking about.

Time to re-connect the gauge set, and find out if the high-side is so high it's damaging the compressor.

Opening the manifold valve is the only way to get a reading, which also opens it up to the entry point for the refrigerant

 

[Frank Enstein]

An A/C shop in Florida said when converting from R-12 to R-134a on mid 80's and early 90's GM vehicles to use a blue ford orifice tube for a Taurus to get the pressures correct. I have done several and the pressures were right on spec.

R-134a cans are generally 12oz. rather than the 16oz. R-12 cans so 4 cans (48oz.) should be about right. Five cans (60oz.) would be too much.

Absolutely check the high side pressure! A high side failure may hurt more than your wallet!

 

[Frank Enstein]

Opening the manifold valve is the only way to get a reading, which also opens it up to the entry point for the refrigerant

You can close the valve to the can before opening the high side valve.