Engine Size: 4.6
Refrigerant Type: 134a
Country of Origin: United States
I'm rebuilding the AC in my '97 F150 pickup after the compressor quit. 6 months ago a mechanic told me that I had an evaporator leak. There's dye in the system, so I looked around with a UV lamp and couldn't find a leak. Now that I've got the system apart to replace the compressor, I'd really like to pressure test the evaporator separately. I've got a nitrogen bottle, and was thinking of pressuring the evaporator up to 100 psi and seeing if it would hold the pressure for 10 minutes.
I have two questions, if that's OK:
1. Is this a good plan, with reasonable pressure and time duration?
2. The evaporator connections are both aluminum tubing with curved flares on the ends. They use those unusual connectors with o-rings and circumferential springs in them: one connection is 3/4" and the other is 1/2". I'd like to tube these up to my nitrogen regulator, or tube one of them up and plug the other, but I'm not sure how to connect to them. I'm afraid I don't even know what that type of connector is called. I'd like to test the evaporator individually, by itself, to convince myself as to whether it has a leak, but I just don't know how to connect it to my regulator.
Thank you very much for the help!
If the evap is pulled from the vehicle, I would plug one end, pressurize to 60lbs as a start, and place it in a tube of water. Look for the bubbles. If none, use up to 90 lbs. If there is a leak, it'll show
At 110*F, very easy to reach with a closed car in the sun, evaporator pressure would see 150 psi static pressure with R-134a, that is all my air compressor is good for. So not afraid to sock the pressure to it.
Connecting the evaporator to the air source can be an inconvenience, can go to a wrecking yard and cut off the fittings, sealing the tube for the plugged end, and jury rigging the other to your air source.
If the evaporator looks corroded, perhaps it just easier to replace it.
About 60 bucks from the host of this site, don't have to tell you, it's miserable if you have to replace it.
Thanks very much for the reply! I haven't taken the evaporator out of the truck, and am really trying to avoid doing so unless the thing has a serious hole in it. If I do have to pull it, I will do the water tank test you describe.
Thank you; very good point about the static pressure of R134a showing 150 psi being a safe test pressure! The evaporator doesn't look corroded, but I can't see all of it, and a nice isolated pressure test will let me sleep easy tonight. I'm headed down to the salvage yard later this afternoon to cut off some spring fittings - good idea!
Thank you both very much for the help!
I usually test em @ 175-200 psi. They blow up @ 300psi
Guys at the airport use liquid nitrogen with a regulator to get anything above 150 psi, can even shoot for 1500 psi, but aircraft shocks only need about 300. I also have a regulator, but have to rent the tanks so don't keep liquid nitrogen handy. 150 psi is plenty and drop it in a water tank. Another way is at the inlet, have a pressure gauge, then a valve, then the air source, put in pressure, then shut the valve, if the gauge pressure holds, it's good.
Prior to testing an evap...it is best to flush and remove all residual lubricants. Settled lube may mask a leak. Air is not a good test medium for evap leak testing. Suggest to use 134a. The evap does not have to be removed from the vehicle, unless one simply wishes to do so.
Recover all refrigerant, flush the system, air purge to remove flush chemicals. Devise suitable fittings for the inlet and outlet. Test first for vac hold. Then simply had refrigerant to the evap. If extra pressure is needed....we use a heater blanket attached to a can of refrigerant to elevate the pressure of the evap. Excessive pressure is not normally needed. Most small leaks are normally evident at pressures less than 125 psi.
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.
Thought the evaporator was in your hand, I wouldn't bother pulling it, would charge with R-134a and use an electronic leak detector, access can usually be gained by removing the blower motor and also checking the drain tube under very quiet conditions as refrigerant is heavier than air.
If you want to do a nitrogen bubble test with the evaporator installed, may have to drive it into a lake.
Iceman255 and NickD,
Thanks very much for your advice! Iceman, I will definitely purge the evaporator first, and then test it with vacuum as you suggest. Unfortunately, I don't have recovery equipment and have to drive into town to get a garage to recover for me. So, I don't want to use 134a as a test gas for the evaporator - I won't be able to recover it. I really liked NickD's suggestion to pressurize the evaporator with nitrogen and monitor for any loss in pressure (over maybe half an hour?) Nitrogen doesn't need to be recovered, of course, and it's both available at a higher pressure and contains less oil than air from a shop compressor.
"If you want to do a nitrogen bubble test with the evaporator installed, may have to drive it into a lake. "
Don't tempt me.
EPA says you can waste a can of R-134a for this purpose, figure less refrigerant would be put into the environment if everyone would fix their leaks. Working with static pressures so don't have to top it off.
Posted this in the wrong spot, where is my coffee pot?
Edited: Sun October 04, 2009 at 8:27 AM by NickD
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