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Known Areas to Check?

Bobby78 on Fri June 01, 2012 10:10 PM User is offline

Year: 1999
Make: Chevy
Model: Tahoe 4dr
Engine Size: 5.7
Refrigerant Type: R-134a

Have a leak somewhere that I'm having trouble finding. Been going on for the last two seasons. System is always down in the spring and needs a charge. This is a 99 tahoe 4dr 4WD with front and rear A/C. Have the truck since new. System all original. Anyway the first year it started was about 2 years ago, I vacuumed the system and it looked to holding vacuum for about 2 hours. Recharged it and it lasted until the end of the season. Started to feel like it was not as cold around October. Had put UV dye in but couldn't find any leaks.
The next season, it needed another charge. Repeated the same proceedure and it held vacuum for a few hours. But this time it leaked down faster. About 6 weeks to 2 months it was getting warm again. Found a leak on one of the schraeder valves so I replaced both of them. vacuumed again, it held, thought I found it. Recharged the system and it lasted way into the early winter. Really thought I had it fixed. This year same thing. It leaked out again. Was thinking of charging it with nitrogen and using soap bubbles. Thought the obvious would be the long hoses to rear evap. But they look clean and free of any oily areas as do the front hoses. Don't see an oily residue in the vents and never saw or smelled any gas inside. So maybe the evap up front is OK.
So I was just wondering if anyone knew of known areas on this truck to check first. I know I can go through the whole system. Removing parts to get a better look, but thought maybe I could save some time with a point in the right direction.

Edited: Fri June 01, 2012 at 10:11 PM by Bobby78

GM Tech on Fri June 01, 2012 10:27 PM User is offline

Compressor belly leaker most likely- look for oily residue in cradle mount or under belly- or in behind one of the grommets on rear line nearest the rear wheels...

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......

Bobby78 on Sat June 02, 2012 11:27 AM User is offline

OK thanks for the tip. I'll take a look and you let you know.

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