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Large leak

beginner on Fri June 29, 2012 2:21 PM User is offline

Year: 1991
Make: Chevy
Model: silverado
Engine Size: 350
Refrigerant Type: R134
Ambient Temp: 110
Pressure Low: 0
Pressure High: o
Country of Origin: United States

I put a vacuum pump on this completely discharged system twice and pulled a 30 minute draw each time . When I shut the pump off ( after closing valves ) I loose all the vacuum within 2 or 3 seconds . I was going to use compressed air to find the leak , but then I read that was not a very good idea because of possible system flammability issues . On the other hand the previous owner told me the system has been discharged for 5 years , so it has had air for a long time and maybe there will be no difference at all in using compressed air at this point . I do not have access to a sniffer and want to do this right , so what is the best way to to approach this ? A leak that fast must be huge and easy to find . Thanks for any help .

Cussboy on Fri June 29, 2012 2:39 PM User is offline

I can't see any flammability issues, the issue with using air is that typically compressed air is not dry, like nitrogen would be.

What was your vacuum reading during this 30 minutes? I would think with a leak that large that your numbers wouldn't be where they should.

beginner on Fri June 29, 2012 5:08 PM User is offline

Thanks for the reply .

On the flammability issue the following caution was from another site . I don't know if it's technically accurate .

Caution – Do not pressure test or leak test HFC-134a service equipment and or vehicle air conditioning systems with compressed air. Some mixtures of air and HFC-134a have been shown to be combustible at elevated pressures. These mixtures, if ignited, may cause injury or property damage. Additional health and safety information can be obtained from refrigerant manufacturers.

On your question of how much vacuum it has , the low side goes deep to about 30hg . The high side reads a little deeper than zero . closing the high and low valves and then shutting off the pump , the vacuum is completely gone in a few seconds . Because it disappears that fast , I'm puzzled by why it still draws a good vacuum .

mk378 on Sat June 30, 2012 11:18 AM User is offline

You've pulled a vacuum so now all the R-134a is gone. Go ahead and use air, though a dry gas would be better. Replace the drier in any case after you fix the leak.

beginner on Mon July 02, 2012 2:25 AM User is offline

Got it ... thanks

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