2010 Expy EL Rear A/C Leak - Any ideas?

[S20Workstation4]

Hi Everyone,

Back in May, I lost the A/C in my expy, and I noticed a hissing sound coming from the rear A/C Unit. After some diagnosing, I concluded it was the evaporator and bought a used Rear HVAC Assembly.

I have the new unit hooked up, I've replaced all necessary seals, and the system still won't hold a vacuum.

I decided to fill it up with 12oz of refrigerant, and there is still a hissing sound coming from the exact same place in the rear unit, even with the new unit installed.

Are there any other places in the rear where a leak could spring? I'm at a loss here.

Thanks in advance,
Joe

 

[twodollars]

On the vehicles I have had with rear ac, which were suburbans and a second gen durango, it was the lines going to the rear unit. Suburban I found aftermarket soft lines, which worked fine. Durango the rear lines were out of production. I ended up finding the leak in a hard line, Evac the system, clean the leak area and sealed it with two part epoxy.

 

[max78]

Did you not pull a vacuum to see if it held before filling?

 

[S20Workstation4]

Did you not pull a vacuum to see if it held before filling?

Yes, I did. The only reason I filled it even when it couldn't hold a vacuum was to try and find the leak.

 

[S20Workstation4]

On the vehicles I have had with rear ac, which were suburbans and a second gen durango, it was the lines going to the rear unit. Suburban I found aftermarket soft lines, which worked fine. Durango the rear lines were out of production. I ended up finding the leak in a hard line, Evac the system, clean the leak area and sealed it with two part epoxy.

Thank you. How could I test and see if the lines are leaking?
Would it be something like a pinhole leak?

 

[twodollars]

I added uv dye to a full charge, ran it fir a while. Then use the light to find the glow.

 

[Stanisz73]

On my 2013, one of the rear lines was leaking. That would have been a time consuming swap since those lines run across the length of the truck. I disconnected the rear lines from the rest of the circuit underhood, and bought a Rear A/C Block Off Kit on Amazon for $18.

I don't have rear air anymore but the front works fine. My Expi is old now and I'm good as long as I have air at all!

 

[pitdexion]

Used part could be bad. Hissing is a huge leak so get some UV dye and a cheap a/c black light. You could also get a block off kit and eliminate the rear though it is nice having cool air blowing on the back of my head.

 

[S20Workstation4]

Used part could be bad. Hissing is a huge leak so get some UV dye and a cheap a/c black light. You could also get a block off kit and eliminate the rear though it is nice having cool air blowing on the back of my head.

That could be a possibility. I UV tested the system the other day, and found a haze of dye around the junction block, where the rear lines connect to the auxiliary unit.
I bought new seals for the lines, but once bolted up, I can see a gap between the blocks. I may have bent the lines during the removal process, due to all the corrosion....

I'm going to be diagnosing more later, I'll update what I find.

 

[S20Workstation4]

Update: It ended up being a pinhole leak in the auxiliary High-pressure line. Put some JB Weld on the line and all is good. A/C has been working great for the past 2 weeks. Thanks to everyone for all the input.


-Joe