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Holds vaccuum but leaks ?

padgett on Mon June 07, 2010 10:26 AM User is offline

Year: 1990
Make: buick
Model: riviera
Engine Size: 3800
Refrigerant Type: 134
Ambient Temp: 90
Pressure Low: 40
Pressure High: 225
Country of Origin: United States

System in 1990 Buick (HR6 compressor) has been converted to 134a. I see a note that dye was added in 2008 and when vacuum pulled got dye in high side valve. Had no pressure as found.

Pulled vaccuum and held for an hour with no change. Charged with 134a until high side was 225-250 at 90F and low was cycling at 40.

Week later is is not-so-cold & cycling faster. No sign of leak either with elecronic detector or UV light and glasses. Ideas welcome.

Just a thought but suspect a slightly leaking schrader valve would not show up in a vaccuum test ?

Note: am amateur but can learn so may be missing something obvious.

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Many Carpets

Edited: Mon June 07, 2010 at 10:43 AM by padgett

GM Tech on Mon June 07, 2010 11:52 AM User is offline

These are known for evaporator leaks-- pull the blower motor resistor o module- and check evap face-- is it oily/greasy? if so there is your leak- How is the air flow out the vents-- can it blow the hair off your forehead? If not your evap face is probably clogged fom the oil leaking collecting dirt and debris--- also- look for compressor shaft seal to be next in line for a leak- is it slinging oil?

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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......

padgett on Mon June 07, 2010 12:47 PM User is offline

Did try sticking the sniffer in a vent & nada. HI fan volume is fine. Just took about an oz to bring vent back to 4xF on 134a at 90F ambient but that is in just two weeks. Pulling ATC blower module is non trivial but will try that. Thank you for the advice.

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Many Carpets

Edited: Mon June 07, 2010 at 12:49 PM by padgett

daman on Wed June 09, 2010 12:03 PM User is offlineView users profile

Quote
Originally posted by: padgett


Pulled vaccuum and held for an hour with no change.
For one that was not long enough one should do few hrs or over night is better,some very small leaks don't show up withing just an hr.

leaks can also be present under pressure Vs vacuum thats why a dye should always be used.



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'00 Pontiac Sunfire 2200 I4 SFI
'99 Chevy 4x4 Z-71 5.7 Vortec v8 CPFI
'97 Chevy 4x4 6.5 Turbo Diesel 2500
'95 Pontiac Grand Am GT 3100 v6 SFI
'88 Chevrolet Camaro IROC 5.7 TPI(49,000 original miles)

padgett on Wed June 23, 2010 3:50 PM User is offline

Has dye in system but only place I saw was around the low pressure schrader on the dryer. Not there now. No reading in sniffer.

Needed about 4 oz in a 32 oz system after 3 weeks. How big a leak am I looking for please ?

-------------------------
Many Carpets

daman on Wed June 23, 2010 5:36 PM User is offlineView users profile

did you check the pump over good with the UV?

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'00 Pontiac Sunfire 2200 I4 SFI
'99 Chevy 4x4 Z-71 5.7 Vortec v8 CPFI
'97 Chevy 4x4 6.5 Turbo Diesel 2500
'95 Pontiac Grand Am GT 3100 v6 SFI
'88 Chevrolet Camaro IROC 5.7 TPI(49,000 original miles)

padgett on Wed June 23, 2010 6:34 PM User is offline

Yes, underneath and on top and all over the compressor (which seems to have been replaced) with yellow glasses and UV flashlight. Nada. From the stickers someone before tried to find it and failed so must be something non-obvious. Did stick sniffer in vent with ac on but nary a twig. Only place I've seen fluorescence is by the low side schraeder but may have happened when system was evacuated. Works fine but loses about an oz of 134 a week.

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Many Carpets

Edited: Wed June 23, 2010 at 6:35 PM by padgett

CCWKen on Wed June 23, 2010 10:03 PM User is offlineView users profile

Check the front of the condenser. It may have taken a rock in the front.

-------------------------
Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

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