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Dad in Law's Old Truck AC Issue

jed_99 on Wed May 19, 2010 1:04 AM User is offline

Year: 1995
Make: GMC Sierra SLE
Model: 1/2 Ext Cab 2WD
Engine Size: 350ci
Refrigerant Type: R134a

Got my father in law's old truck, low mileage (78,000 miles), but not looked after these last few years very well. For one, AC didn't work. I disassembled the radiator away from condensor and cleaned out both. The local tech added some refrigerant which worked for about 2 days and then air temp was ambient again.

Pulled the caps off the schrader valves and they're leaking on the metal lines to/from AC compressor. So, I'll have to replace those valves from ACkits, but while I'm at it, what other items should I be replacing, as some preventative maintenance?

This is, of course, assuming everything will be working again when the valves are replaced and refrigerant topped up again.

Chick on Wed May 19, 2010 7:35 AM User is offlineView users profile

You may have other leaks, you should try to find and fix them before you recharge fully, if you have access to an electronic leak detector, check every connection, common spots on those are the shaft seal, and body O may see oily dirt build up around the front center of the hub on the compressor.. If you just change the shrader valves, add UV dye to the system when you fill it, then use the UV light and glasses to locate the leak(s)..

Email: Chick


Freedoms just another word for nothing left to lose

GM Tech on Wed May 19, 2010 10:04 AM User is offline

I agree with Chick- the caps seal off any valve leaks and are not your major leak point-- you probably have a shaft seal leaker-- look for an oil spray line on underside of hood- and for the greasy/oily build-up on front of compressor clutch

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......

Cussboy on Wed May 19, 2010 2:23 PM User is offline

Also check the compressor body and the high side crimps of the manifold hose assembly, I've had leaks both places on my '94 (OK, Suburban), but mine's got 200K.

Edited: Wed May 19, 2010 at 2:23 PM by Cussboy

jed_99 on Thu May 20, 2010 1:22 AM User is offline

I knew I forgot something in my first post - I had them put dye in with the refill and the valves are where it showed. No oil sprays on anything else, surprisingly. So should I be adding an inline filter, changing the receiver/dryer while I'm in there and ordering stuff?

mk378 on Thu May 20, 2010 9:14 AM User is offline

There will always be dye on the service ports, it blows out every time a gauge hose is disconnected. Most people think their ports leak when the leak is usually somewhere else. The whole system should be checked carefully.

A leak that empties the system in two days could be detected with an electronic leak detector or even soap bubbles. Like the others said, GM compressors are infamous for leaking. Also examine the condenser for holes due to corrosion, damage from stones or other road debris.

Edited: Thu May 20, 2010 at 9:16 AM by mk378

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