Have a 2001 expedition with 5.4L. Had a new compressor, acumulator, orifice tube installed a little over a year ago, now it is blowing out the valve on the manifold hose after it sits then you start it. a/c blows 50 degrees with ambient at 85. low side pressure was at 40psi and high near 200 or so. it ran for about and hour and i parked it. Sat for about 20 min and went out to start it and it blew it all out the relief valve. Any thoughts????????????

 

It does sound like the system was overcharged. To have lost some refrigerant twice and still pull to only 40 could indicate quite an overcharge or a possible restriction or even a possible compressor problem, but to try to diagnose things like this without the gauges hooked up and not being there is pure speculation on my part.

 

I put in 3.8 lbs, also installed new fan clutch yesterday, seemed to not be pulling a lot of air. It helped with the air flow. Its been working this whole time and now it wants to shoot it all out after it sits and is restarted.

 

I wonder if the system was properly evacuated before charging? I worked with vacuum quite a bit and learned something about vapour pressure: When you apply vacuum to a mixture of substances the most volatile substance gets sucked out first. The air is already in the gaseous state, so that goes first, then solvents like methylenechloride, acetone, ethanol etc. One of the hardest ones to remove is water.

When you replaced the AC components you obviously opend the pipe endings and introduced ambient air which contains moisture. With a system this large I would run vacuum at 5 microns for 1 hour to get the water out. Actually I would ask hanky if he would agree with that and then take it to a pro and ask him to do it that way.

 

I do agree with everything you said bluewind!
I'm curious about a few things,
who really did the A/C work when all those components were changed,
If the system wasn't evacuated properly how could it have worked OK up to now?
After the system is shut down and the system pressures stabilize, what is causing the pressure on the high side to go past the blow-off point of the relief valve ? There is the possibility the relief valve is just defective.
What is the high side pressure on the gauge when you allow it to sit for that period of time and start it and turn the A/C on? If the pressure is within the normal range and it still blows off, the relief valve may be the problem.

 

I run a repair shop and have run in to the same issue on one we are working on now. We replaced the Compressor, Condensor, Drier and Orifice due to a compressor that had locked up. The system ran good for 3 days and the customer started the vehicle and was idling first thing in the morning. After a couple of minutes the system purged from the blow off valve. We have had the vehicle two days and tried recharging, reflushing the lines. Once the system has been recharged we have not been able to duplicate the failure while the ac gauges were hooked up. The customer has come to pick the vehicle up twice and within minutes of him getting in it the system has purged. I'm cusrious if growapair ever figured out / solved this issue?

 

Update:

We finally got the system to act up while the AC gauges were hooked up. The high side pressure readings climb right beofre the system is purging. We are going to swap out the condensor and orifice suspecting one or the other may be defective. I will post a confirmed fix but would be very curious to know if the original poster was able to correct his issue.

Thanks