Won't hold vacuum, but no dye comes out
Posted: Sun Apr 30, 2017 12:58 pm
Hello, all. I'm trying to get the A/C working in my 1995 Mitsubishi Mighty Max. When I bought it 2-3 years ago I put some work into getting it running, then got stumped, got busy, and gave up on it. Fast forward to now, I'm trying again to get it working, but I'm still completely stumped on the same problem. I'm close to giving up and taking it to a shop, but if i can fix it myself within a reasonable amount of time I'd prefer to, because my experience with shops is that they usually charge me an arm and a firstborn for something that I later find out I could have done on my own in the course of an afternoon if I had just known what I was doing to begin with.
The Short Version
When I try to pull a vacuum on the system, it won't hold at all. It won't pull more than -20, and as soon as I turn the pump off or close the gauge, it quickly goes back to 0. This obviously suggests a huge leak, but I can't find it anywhere: when I add dye and refrigerant, I don't see it coming out anywhere. Some of the previous work that I had done suggests that the leak should be around the connections for the compressor or for the evaporator, but no dye comes out there upon close inspection. Before giving up last time around I had inspected the O-rings at those points, and oiled up and installed new O-rings, in spite of the fact that the previous ones looked fine, which suggests that either 1) that's not the problem, or 2) I did it wrong twice.
The Backstory
This truck has not had working A/C for the duration of my ownership of it. When I first got it, I found that there was a huge leak in the condenser. Nobody makes new condensers for these trucks anymore, but I was very lucky in that a friend found a complete A/C system which was still pressurized (thus, not leaking) in a similar truck in a junkyard, which he pulled for me. I then replaced the condenser and the dryer/accumulator and vacuumed/recharged the system. It held a vacuum/charge, but the air was not cold. According to the pamphlet that came with the A/C recharging system that I had bought at the store, the pressure gauges were telling me that the compressor was bad and needed to be replaced. I got busy and didn't work on it for two months, but when I came back to it two months later it was still pressurized, which tells me that it was not leaking at all at that point. I then replaced the compressor with the previously non-leaking one from the junkyard (which was super simple: I have no idea why shops charge $600 to do this!). I also disconnected the evaporator lines because I originally intended to replace the evaporator and/or expansion valve, but I then decided that it was more trouble than it was worth and reconnected it. Then when I tried to pull a vacuum, I got to where I am right now: it won't pull a vacuum at all, which suggests a huge leak, but the UV dye won't come out anywhere. As mentioned above, logic would suggest that the most likely location of a leak would be at the compressor line connections, but no dye comes out there, and replacing the O-rings made no difference.
The Short Version
When I try to pull a vacuum on the system, it won't hold at all. It won't pull more than -20, and as soon as I turn the pump off or close the gauge, it quickly goes back to 0. This obviously suggests a huge leak, but I can't find it anywhere: when I add dye and refrigerant, I don't see it coming out anywhere. Some of the previous work that I had done suggests that the leak should be around the connections for the compressor or for the evaporator, but no dye comes out there upon close inspection. Before giving up last time around I had inspected the O-rings at those points, and oiled up and installed new O-rings, in spite of the fact that the previous ones looked fine, which suggests that either 1) that's not the problem, or 2) I did it wrong twice.
The Backstory
This truck has not had working A/C for the duration of my ownership of it. When I first got it, I found that there was a huge leak in the condenser. Nobody makes new condensers for these trucks anymore, but I was very lucky in that a friend found a complete A/C system which was still pressurized (thus, not leaking) in a similar truck in a junkyard, which he pulled for me. I then replaced the condenser and the dryer/accumulator and vacuumed/recharged the system. It held a vacuum/charge, but the air was not cold. According to the pamphlet that came with the A/C recharging system that I had bought at the store, the pressure gauges were telling me that the compressor was bad and needed to be replaced. I got busy and didn't work on it for two months, but when I came back to it two months later it was still pressurized, which tells me that it was not leaking at all at that point. I then replaced the compressor with the previously non-leaking one from the junkyard (which was super simple: I have no idea why shops charge $600 to do this!). I also disconnected the evaporator lines because I originally intended to replace the evaporator and/or expansion valve, but I then decided that it was more trouble than it was worth and reconnected it. Then when I tried to pull a vacuum, I got to where I am right now: it won't pull a vacuum at all, which suggests a huge leak, but the UV dye won't come out anywhere. As mentioned above, logic would suggest that the most likely location of a leak would be at the compressor line connections, but no dye comes out there, and replacing the O-rings made no difference.