Here's my problem: When I purchased my truck (94 F150 5.8L) a couple of years ago the PO said that the a/c had a slow leak in it and that he would just recharge it at the beginning of the summer and it would last for the entire summer. So last summer I did that and it only lasted a month. I found that the pressure sensor on the accumulator (aluminum cylinder on the low side of the a/c) had been over tightened and the threads were stripped out causing it to vibrate and leak out all the pressure. I replaced that and recharged it. This time it only lasted a cuple of weeks. So I added dye/stop leak to the system and a can or two of R134A. This time it held 30-35 psi for over a month. I figured the stop leak must have sealed up a leaking o-ring or something so I added in enough R134A to bring it up to the proper pressure for the air temp. Now two weeks later the system again has zero pressure in it and I can not find where it is leaking from. There is no dye what so ever on any of the connections that I can see. Are there any hidden connections that I am missing? I know one of the tubes goes around the radiator some where that I can't see. Are there any notorious spots that the a/c systems leak from in these trucks?

 

I feel your pain. Put a new compressor on mine, still wouldn't hold pressure for long. Replaced both lines and still looses. I tried some dye, nothing. Only place it's noticable is the low pressure schrader where you put it in at.

Ugh. I was told to replace the schrader valves, but the lines are new? Tiawan made crap??

Lucky it's fall now and don't need air. Don't have to worry for another 7 months.

 

There is a good chance it is the rubber hoses themselves and not any of the connections. it could also be in the evaporator.

And freighttrain, i have to ask, but did you try to tightem the valve core that is in there?

matt

 

All AC systems seep, You really need to have a legit set of ac guages so you can read the low and high side pressures. you need to know the amount of refrigerant AND the amount of oil in the system for it to operate properly. r-12 and r-134 use different oils for lube and cannot be mixed!

 

Don't tell the EPA that, they will have to change their rules

matt

 

Sounds like I am going to be stuck taking it to a shop. If I was still living in Idaho or Utah I wouldn't even worry about it but I am currently living in Vegas and you die with out air. Luckily I have a company vehicle for during the week!

 

Every system AC "seeps" No leaks allowed though... haha

 

Did you look around the compressor? My 93 was leaking between the compressor parts and could only see oily spot the dye did not show. Vacuumed it down and it would not hold overnight. Wound up changing the compressor but also bought o-ring kit fromAdvance and went ahead and changed all the o-rings and flushed the system with alcohol (denatured, isopropyl contains water) Pulled a vacuum for 24 hrs works good. A lot of black stuff came out of the lines when I flushed it.

 

Thats good advice, altough you should be able to see the dye in the oil with a black light if there is a leak. Unless it the o ring and your refrigerant level is so low that outside pressure is greater then the inside pressure and it slowly leaks out past the o ring while the system is not in use which will cause you to take on air in the system.

 

An electronic leak detector can find that leak in minutes.

Sticking the probe in the AC outlets will quickly detect
a leaky evaporator. Using dye is the poor mans method and
as you've discovered only as good as what you can see.

Take it to a shop and pay them to diagnose where the leak
is then fix it your self.

 

I'd have to agree with those who suggest taking it to a shop with the correct equipment. Unless you can pull the system into a vacuum to remove all the air and moisture, it wont function 100%. One thing that I need to ask, when you looked for the leak, did you use a good UV light and yellow glasses? Large leaks will show up as a green streak, however it's the small ones that cause the comebacks. Check the evaporator drain tube, the entire condenser, the lines, hoses and fittings. The correct way to charge a system is to put in a measured charge (by weight), charging by pressure is a shot in the dark.

 

Yeah, I don't have the correct equipment to diagnose the problem so I am going to take it to a shop and let them handle it.