AC doesn't leak when it's running... (1 Viewer)

[swank60]

Anyone care to venture a guess on this one?

With the truck off and quiet, I decided to go over the AC crap one more time before I put it in the garage. I looked at the expansion valve in the dark with my UV light and glasses and have determined that the glowing I saw earlier in the day was just residue. Good. I don't have to pull that crap out again.

On a whim, I added freon to it at the low port on the compressor. It started hissing at me. Found my leak. Here's what's weird - I can fill the system up with freon and let it run all day long without a problem - when I shut it off, it starts leaking - and as I said, I heard the stinkin' compressor hissing when I increased the pressure tonight.

Why? I mean, what kind of sense does that make?

And since it really doesn't make any sense, does it point to a specific problem that I should look at? Seems like if something doens't add up like that, it points to something specific.

(the one thing that does make sense out of this whole stupid deal is why it'll hold 30Hgs of vac without a problem. It will not, however, hold 65-100 psi of freon.)

I hate my truck...

 

[NocalFJ60]

Maybe the hole that is leaking gets sucked in and closes when you pull a vacuum but when you pressurize it opens and leaks?

 

[benw4x4]

What is the pressure when its running,is it the low or high side that leaks if you replaced the expansion valve you could also have a problem with the rec drier tha causes the press to jump up instead of balancing out when it is turned off. If that is the case it just found a weak point in the sys to bleed thru, and does the low side draw down low around 2500rpm, if not you could have a pump prob.

 

[swank60]

Ben - the pressure does draw down on the low side when you start up the compressor and run it up to 2500 rpm. Guess that's why the thing leaks when it's off, not when it's on.

As for the rec drier, I replaced it when I replace the expansion valve, but I didn't replace it the last time I tore the system down (I know they say you're supposed to, but I assume they suggest that under normal cirrcumstances, when you aren't tearing the system apart every couple of weeks.)

I'll put the manifold on it and put more freon in it tonight maybe and see what it reads - I'll also shut it off with the manifold still on and see if I can figure out which side it's leaking from.

 

[benw4x4]

That really is odd the only other thing i could think of is the condensor but you would notice that I am sure. Wish I could be more help.