A/C leaking and will hold vacuum

[Blaine.D]

Hello Y'all

I'm basically at my breaking point with trying to figure out the a/c leak on my comanche. Short story the heater core gave up the ghost and needed to be replaced. At the time the a/c hold a charge but was leaking on the high side valve. I have previous done a 134a conversion. So I ordered a 134a conversion kit from jeep air to get proper fittings and an evap core from rockauto.  The evap core and dryer made a woosh sound so I at least know these are likely not the source of the leak. Currently the evap core, compressor fittings, and dryer was replaced. The past couple days i keep getting the same results of vacuuming the system down to 30 inhg and leaks to 20 inhg within a hour. So far I replaced the orings multiple times on the evap core and lines going to the evap, compressor, compressor fittings, and dryer. Replaced the expansion valve.  Every time the same results. I even try to add compress air(made sure shop air compressor was drained with no trace of water and had a dryer system on pressure hose) about 40 psi to the system and spray connections with soapy water and no bubbles. 

[AeroNautical]

This wouldn't be the cheapest method, but maybe try using a dye with the pag oil and service the system as soon as vacuum is placed on it. You'll either see it right away, or it will accumulate where ever the leak is over the course of a few days. Might give you a better idea of where the leak actually is. Lets hope it's not leaking at the evaporator, that would be another dash pull...

[AZJeff]

1 hour ago, PFCLeist said:

This wouldn't be the cheapest method, but maybe try using a dye with the pag oil and service the system as soon as vacuum is placed on it. You'll either see it right away, or it will accumulate where ever the leak is over the course of a few days. Might give you a better idea of where the leak actually is. Lets hope it's not leaking at the evaporator, that would be another dash pull...

The method you suggest is commonly used at professional shops to find leaks in an auto AC system.   The system needs enough refrigerant in it to cause the compressor to cycle.  Once that happens, the dye that is added into the system is then used with a black light to find the leak(s).  

 

If the leak is in the heater box (due to a bad evaporator), the only way to find that is with a refrigerant "sniffer", but I am betting you will find it via the dye and blacklight.