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Noisy R4 Compressor

MightyMax on Thu July 28, 2011 3:15 PM User is offline

Year: 1991
Make: Chevrolet
Model: c1500
Engine Size: 350
Refrigerant Type: R134

Wondering if anyone can give me some ideas on this thing.

Ok, about 2 yrs ago I swapped out Accumulator, Compressor and Orifice tube.....didn't flush the system.
I put in the charge and it blew cold, but started making a loud awful noise at the compressor...
So I though I screwed up the compressor, maybe didn't put in enough oil.
So I bought and replaced (about 1 week ago) Compressor, Accumulator, Hose Assembly, Orifice Tube, and condenser.
If you want, there is a little more detail here: http://www.gmtruckclub.com/forum/showthread.php?68612-Condenser-Fan/page3
First post on that page.

Needless to say, the new compressor is making the same God awful noise.
Seems to be fine when I first crank the engine and it is cold....
Noise starts up when the engine temp gets over 200
I can drive down the road and things seem/sound fine, but come to a light or stop and things start getting loud again.

Any idea about this thing??
It is driving me crazy.

GM Tech on Thu July 28, 2011 3:47 PM User is offline

Those older trucks had a steel horseshoe bracket that all the accessories bolt to...yours is most like cracked where it attaches to head-- take compressor off and look at all the bolts that attach horshoe bracket to engine- there may be a broken/sheared bolt, or a bolt backed out---seen it a bunch -- seen it so bad you could lay a screwdriver on top of compressor and it would jump up and down an inch! and you could not read engine oil on the dipstick, it was vibrating so bad.....

This is why GM went to aluminum brackets......

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

MightyMax on Thu July 28, 2011 3:59 PM User is offline

If that is the case,
How do I fix it??

Cause it seems that the thing requires the whole front of the engine to be pulled off.

Edited: Thu July 28, 2011 at 4:02 PM by MightyMax

MightyMax on Thu July 28, 2011 4:07 PM User is offline

Would over-tightening the mounting bolts on the compressor cause this problem??

Because this issue only arises after engine temp is over 200

Before that, it can sit and blow cold and be just fine and quiet.

Edited: Thu July 28, 2011 at 4:08 PM by MightyMax

TRB on Thu July 28, 2011 7:50 PM User is offlineView users profile

There have been reports over toughen bolts will cause leaks in the case seals.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

GM Tech on Thu July 28, 2011 9:44 PM User is offline

No, the overtightening of compressor bolts would not matter--- the steel bracket vibrates and the bolts shear-- the two behind and under compressor are the ones I'd check first- remove compressor and look for bolt heads missing- from being sheared .....the noise is from bracket to engine interference/vibration, not compressor to bracket....

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

MightyMax on Thu July 28, 2011 10:32 PM User is offline

Ok, I will take a look at that tomorrow and see if I see anything with those mounting bolts.

But this sounds like it is from the compressor......it is making a God awful noise

TRB on Thu July 28, 2011 11:50 PM User is offlineView users profile

Quote
Originally posted by: GM Tech
No, the overtightening of compressor bolts would not matter--- the steel bracket vibrates and the bolts shear-- the two behind and under compressor are the ones I'd check first- remove compressor and look for bolt heads missing- from being sheared .....the noise is from bracket to engine interference/vibration, not compressor to bracket....

You're the expert on the GM stuff. But I could sworn I read something on the body leaking if you over tightened the bolts. Either way thanks for clearing it up.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

MightyMax on Fri July 29, 2011 7:38 AM User is offline

Ok, I looked (without removing compressor for now) and it appears that there is a bolt that is missing.
It appears that the bolt would go through the accessory mounting frame and bolt into the engine just under the passenger side valve cover.

So question is now, where can I get a bolt that will fit this thing??

@TRB
I thought I had also read somewhere about overtightening the compressor mounting bolts could cause problems.

Edited: Fri July 29, 2011 at 7:39 AM by MightyMax

GM Tech on Fri July 29, 2011 8:15 AM User is offline

bolt is probably not missing, but sheared off-- look and see if it is a blind hole or something is in it...stick a small probe in it. Dig in your used bolt buckets to find one that matches the one next to it. Or visit your local hardware store...

The leaky compressor rumor was from HT-6 high mount overtorquing-- not R-4 compressors...and it is a rumor-- leaks on HT- are from corrosion, not torquing and twisting...otherwisw low mount HD-6s would NOT leak.......but they follow the same scenario...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

GM Tech on Fri July 29, 2011 8:16 AM User is offline

bolt is probably not missing, but sheared off-- look and see if it is a blind hole or something is in it...stick a small probe in it. Dig in your used bolt buckets to find one that matches the one next to it. Or visit your local hardware store...

The leaky compressor rumor was from HT-6 high mount overtorquing-- not R-4 compressors...and it is a rumor-- leaks on HT- are from corrosion, not torquing and twisting...otherwisw low mount HD-6s would NOT leak.......but they follow the same scenario...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

MightyMax on Fri July 29, 2011 9:48 AM User is offline

Well there is nothing there...I got a bolt from AutoZone and was able to finger tighten it in, so I just need to wrench it in now.

I am like 3rd or 4th owner of this truck, so I am still trying to piece things together with it, and figure out what the heck they were planning with it.

It is from North Carolina, so I am not sure if they were setting this truck up for towing or for racing.
They put dual exhaust on it, an Edlebrock Intake Manifold, a raised TBI.....and they stuck an nail in the EGR suction line to disable him.....
The original Compressor on this thing when I got it, had the clutch ripped off and the low pressure switch was removed.....but the system appeared tight and sealed when I removed the compressor.
They have an after market oil cooler mounted in the front of the condenser as well as a transmission cooler also mounted in front of the condenser.

I am seeing leaks from the radiator on the drivers side of the radiator, so I will need to replace him soon....

MightyMax on Fri July 29, 2011 10:40 PM User is offline

@GM Tech

Dude, you are the $#!%.....
This stupid problem has been buggin the crap out of me for like the last 2 yrs.
But it looks like that bolt fixed the problem....

What sucks is I just spent a few hundred dollars to rebuild the system and it came down to a $2 bolt......

Thanks a bunch.....

But I think the problem has been corrected....crossing my fingers anyways.

GM Tech on Fri July 29, 2011 11:37 PM User is offline

Nice to know we fixed one-- not that often you win---I did noise and vib diagnostics for 20 yrs--on warranty issues primarily-- have seen 6 compressors get changed due to a broken bolt on those old style horseshoe brackets......

Glad you're happy-- ain't the internet wonderful?

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

MightyMax on Sat July 30, 2011 8:10 AM User is offline

Yes it is a very wonderful thing.....I figured if I kept asking around, ideas would keep coming up and eventually it would be the one that worked.

Thanks again mate.

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