Typical Foxbody A/C leak spots

[Trentman2004]

Hello,
I have a 1990 5.0 Convertible and i'm trying to figure out where my A/C leaks are. I recently used the UV dye and found leaks at the connectors for the condenser so i replaced the orings and springs. I have also replaced my air dryer and orings to the compressor. I took it to a buddy's shop and he put a vacuum on it but still is not holding the vacuum pressure. None of the original 1990 components have been replaced except that the nozzles were converted to R-134.

Any input on where typical AC leaks are? Also, does the evaporator under the dash prone to leaking and if so, how do you check with out ripping the dash out first?

Thanks

 

[RaggedGT]

30 year old parts , what are you gonna do
With UV dye in the system, an option would be to charge the system and run it . Then follow all the lines,check the compressor, and look for the dye coming out of the evaporators drain

 

[Mustang5L5]

Any of the O-rings not replaced are potential leak sources. R-134A tends to easily seep past the older O-rings. Plan to change them all out, along with the orifice tube, and the accumulator before pulling a vac and refilling the system. What i'd do now though is refill with the UV dye, find the leaks, fix them, and then replace the orifice and accumulator.

 

[Trentman2004]

Mustang5L5, when you say UV dye, I assuming you mean the R-134 can with the UV dye in it?

 

[Mustang5L5]

They have dye that is not in r134a.

You'll need some pressure in the system however for it to leak out.

 

[Trentman2004]

So I hook up a gauges and a vacuum pump this weekend and let the pump run for about 10 minutes and did read a negative pressure on the low side gauge. I shut off the valve and left open the port valve to the compressor and closed the hot side valves. I could literally watch the pressure go from -30 to 0 in about 7-10 minutes, which tells me the leak is pretty substantial somewhere.

I will but putting in some dye tonight to see where the leak is actually at. I hoping its either the condenser or compressor, cause pulling the evaporator seems to be quite an undertaking.

feel free to comment or suggest.

thanks

 

[junkyardwarrior]

Schrader valves leak sometimes. Evaporator leaks sometimes. Condensers leak sometimes. O-rings and connections. Back at the firewall there are the two connections to the evaporator, mine both leaked there. Compressor seals can leak too. Look for oil and/or dirt residue around the nose of the compressor, behind the clutch assembly. The compressor itself has 2 gaskets and I've had one of those leak too. I've seen manifold gauge connections leak too so don't rule those out. The compressor seal is available by itself and it's not real expensive. If the compressor is original, it may be a good idea to just replace it. Ask the seller how much (if any) oil is in the compressor's crankcase. It makes a difference. Too much oil charge in an a/c system will reduce it's ability to transfer heat.

There's no orifice "tube". The orifice is built into the metal line and is not replaceable, well it "is" but you have to replace the whole line, OR cut it, remove the orifice, splice the line back together and then put your aftermarket orifice tube in at the evaporator inlet. Not a fun job.

Once you find your leaks, and FIX them, you can do a couple things. I generally vacuum & check first, then use nitrogen to fill the system to about 200 psi and let it sit. But not everyone has the capability to use nitrogen. Sometimes a system won't leak under vacuum but will leak with pressure. Once leaks are fixed, it would be a good idea to replace the dryer assembly, reassemble, triple check for leaks using nitrogen (if you have that capbility)...if ok, vacuum to 500 microns for 1 hour, and then charge the system properly. Properly meaning by weight, these are critical charge systems and one can't accurately charge by psi alone and expect the system to work efficiently.