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Can't find R-134a Leak?

kourso on Fri August 24, 2007 1:10 AM User is offline

Year: 1994
Make: Chevrolet
Model: Pickup
Engine Size: 350
Refrigerant Type: 134a
Country of Origin: United States

Hey Guys,
I need some help. I can't find the refrigerant leak using UV Dye/Light and/or electronic leak detector (Robinair). But no doubt, it has one, I have to add 1/2 can every 2-3 days, the compressor starts cycling rapidly and interior a/c vent temp is very warm.
Everything goes well after adding the freon to the system. I have tried to find the leak with the a/c on and then checking/testing after a/c system shutoff. I even tested the auto interior after an overnight rest. No good, the only other thing I heard I could do is look up into the evap. core housing drain line to see if there is any dye and/or running the elect. leak detector probe in there. The only problem is there may be some old dye in there from 2 yrs. ago when I replaced the evap. core and compressor. I have looked at the compressor shaft / inlet/outlet manifold/switches for any leak with both methods. I checked the condenser front and in/out fittings as well as other hoses and fittings including the accum. fittings.
I am baffled by NO OBVIOUS SIGN.
WHAT CAN I DO TO FIND THIS LEAK, Should I try tightening all fittings more even though none show leakage.

kourso on Fri August 24, 2007 1:14 AM User is offline


I did check the schrader valves too, the high side leaked last week and I pressed it down several times,and it sealed and still shows good now. The low side hasn't had any leakage and I keep port caps on w/o-rings.

iceman2555 on Fri August 24, 2007 9:40 AM User is offlineView users profile

This is a serious leak.
Try placing the probe of your leak detector into the HEATER outlet over the tranny hump. Start the engine...engage compressor....blower set for second/third speed.
Often the burst of air will move the escaped (if this is the area of leakage) refrigerant thru the plenum and out the vents....heater outlet being the lowest point. This method has proven successful on numerous occasions.
Received a new leak detector last week. One of the heated diode units. Tested it yesterday on a late model Gm 1500 with a 'ghost' leak. Had used several different units to test and could not pin point the leak. Of course, not being able to locate under the hood leaves only one other suspected area....but....always want to be sure before expressing that. This unit worked exceptionably well. Had been testing one of the 'cold' diode leak units for a period of time and it did not indicate the leak. They are not cheap...but for the pro's this is one to seriously consider.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

GM Tech on Fri August 24, 2007 12:14 PM User is offline

I suspect the compressor shaft seal- those replacement compressors have yet to use the double lip seal that I know of.....if you pull th eclutch off- I'll bet you can see the oil and dye.......A good sniffer will find that evasive leak-- you have a gross leak- should be a piece of cake to find with a good electronic leak detector.............

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......

Dougflas on Fri August 24, 2007 12:26 PM User is offline

try putting a plastic bag or a shower cap over the front of the compressor to help find seal shaft leaks

iceman2555 on Fri August 24, 2007 2:18 PM User is offlineView users profile

Not sure how many of the aftermarket mfg'ers are using 'double lipped seals' but it is known of one that is for sure.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

kourso on Fri August 24, 2007 5:59 PM User is offline

Thanks guys,
I will try it all and report back. I saw a small dap of UV dye on one spot in the clutch hub bolt interior. I want to clean it off good and see if it returns. It didn't appear to be much with the UV light. What about the back side of the condenser ? Is it worth loosening the radiator and tilting to see the back side with the UV light ?
I put the elect. leak detector all around the condenser front/sides, nothing there.
I put the leak detector probe into the evap. core drain line elbow and nothing there with the a/c completely off.
Keep the ideas coming, I HAVE A GOOD LEAK TO FIND,
I will Let you know the villain whenEVER I find it,

kourso on Wed August 29, 2007 4:20 PM User is offline

I think I finally found the 134 leak. I was rechecking the a/c system as the charge was almost completely gone after I had been checking all system components over the course of over a week. I heard a hissing noise as I was recharging the system. I put my elect. leak detector (Robinair) by the acc. cycling switch where I heard the hiss and it went off continually where previously it didn't sense any leak days ago.
The cycling switch (plastic) body at the threads was cracked and I think as the recharge pressure increased it cracked more, that could explain why the leak became larger with time. I partially recharged the a/c system without the cycling switch installed as I couldn't buy a new one until the next day. The a/c system pressure held fine by the next day so I knew that I may have found the leak source.
I reinstalled the new cycling switch and put it on with a new o-ring hand tight only and checked for any leak.
Once I recharged the a/c system to 35# low side, my vent temp is on the cool side but not as cold as originally and the accumulator is barely cool but the evap. core is putting out a good quanity of drain water.
What could be the problem, could it be air in the a/c system as I didn't pull any vacuum prior to recharging. The a/c system wasn't opened but the refrigerant leaked down to just about zero.
Please send me some suggestions.

Chick on Wed August 29, 2007 4:30 PM User is offlineView users profile

You need to recover the refrigerant and recharge the factory amount bac into a deep vacuum. Your cold air will then return...Hope this helps..

Email: Chick


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