Hey fellas,

I know I have a leak because the freon leaked out, Duh!! So I pressurized the system with 80 psi of compressed air and noticed that in about five min the press dropped to 75psi.

I grabbed the soap water mixture and sprayed everywhere, on the rubber hose, on the a/c comp but still can't seem to find a leak. I checked the high and low press ports too just in case the schrader valves were leaking. The leak could be in the evaporator box, in which case, the leaky air would be coming out of the drain hose. So, I stuck the end of the drain hose into a bottled water to look for bubbles, and NADA.

I do this on all of my vehicles to find a freon leak and it works really well.

So, I'm now pulling a vac on the system, then will introduce UV die after work today, then recharge the system enough to trip the press switch which will make the compressor run. I know I can bypass the trinary press switch and engage the compressor coil but I wanted to build up freon pressure with uv die. I just hate wasting a can of freon which is now becoming more $$$$.

If it turns out to be something inside the evaporator, I might try this as a stop gap before tearing out the dash.
A/C EasySeal Nu-Calgon

I'm curious to find out the most common places our a/c systems tend to have leaks. Thanks for your input.

Seem to see a lot of 4th gen's experience leaking evaporator. Had that occur on my '05 and finally identified based on UV dye - leak was not large and it took a long time to build up so that I could see slight dye residue on the frame by the drain tube. Chased that leak for over a year - big job to replace so wanted positive confirmation it was the issue. Once I removed the evaporator, the dye spots were apparent.

FYI - no shop will want to evacuate and recharge your AC system after you use a stop leak product like the one you identified. When they evacuate the system and recover the refrigerant (which they are required to do by law), the sealant can clog up their very expensive machine. Typical to test for presence of sealants before hooking up the machine. Unless your T4R is near the end of it's life, I wouldn't use it. My friends '05 had an evaporator leak and it was not worth the money to have someone fix it so he used the stop leak....it did not fix the issue.

Thanks for the reply. I don't use shops for anything on my rigs, and I have my own A/C setup so I'll be doing it all. Figured I'll try the stop leak route, and it's totally a gamble, I get it. Tearing that evap is a royal PITA.

My 4runner has 400k and still going strong so I don't think it'll die any time soon :-)

Sounds like you got it in hand....