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Find Tiny AC Leaks???

G

gottarollwithit

Cooks with motor oil
Joined
Aug 23, 2008
Location
nut Sac, Cali
Been noodling on how to find a small AC leak. I got a Jeep that i can pull a vac on, but it loses it after about 15 min. It's a pretty slow leak, but some of the AC components are buried under the dash.

What's the fastest and cheapest way of finding this leak??

From what i've seen, pressurizing the system with nitrogen and then spraying with soapy water would be the easiest way to go. Unfortunately, i don't have access to a bottle of nitrogen, nor do i have the fittings to plumb this up. Cost of that stuff would probably exceed what it'd cost to pay a shop.
However, i do have some argon for TIG welding. As an inert gas, i assume that would work equally well? How the heck would i plumb that up to push in 100 psi+?

Alternatively, I have some r134 and dye. Does this method actually work for tiny leaks????

For a big leak, i could envision the dye method working great, but for a pinhole leak, does this take several fill/leak til empty cycles until i can actually see it?
 
Yeah, a 15 minute vac leakdown should be pretty damn easy to spot with dye.

That's only 13 - 14 psi pressure difference leaking down in 15 minutes.

The dye/UV flashlight works a bit better if it's somewhat dark. Wait until evening to look, or if it's in a garage, turn off the lights and close the door.

Or maybe my UV flashlight is just dinky.
 
Easiest way to spot leaks is to inject an ounce or two of UV dye into the system mixed with a bit of correct compressor oil(PAG/POE/PAO) and then give it a partial charge and start the Jeep up and let it run for an hour to push it through the system. A decent UV light will help locate even the smallest leak. The best way to tell if you've got a leaking evap core is to look at the HVAC drain that comes through the firewall. If it's leaking; the dye will run with condensation and drip out the drain tube and get lit up like a French whore in church. Don't use anything that has leak sealer, that will sludge up your system so bad.
 
UV dye is the best way. Saying it's a Jeep there's a good chance its the evaporator core. They have a very high failure rate in Chrysler products from the 1990s-in to the 2010s. Check the evap drain for dye dripping out with the condensation water.
 
freevolvos said:
i have found the shrader valves to be leaking on two out of three cars i own
Click to expand...

I had one on an old Toyota that wouldn't hold a vacuum, but would hold pressure. Which was annoying to diagnose. I just got lucky and heard it hissing when I took the vac pump off.
 
OP look for the oily mess covered in dirt on A/C parts. Compressor.... Hoses... A/C drain 'chicken lips' Easy to find a huge leak. Pressurize to 150psi with shop air and listen. Even better includes adding dye... Compressed air to get the system to operate.
 
Compressed air does work to find huge leaks.

For sneaky ones we overcharge the system and reinspect. A sniffer works great too.
 
Anymore I just use compressed air and Dawn soap in a spray bottle. I second that comment about the Schrader valves, all of mine leaked there or pin hole oxidization on the condenser. HF has a pretty cheap gauge setup for the AC systeml
 
OK, i've dumped in some UV dye and charged the system. Not really sure if it's under or over charged. I just dumped in some r134 until the low side hit 30 psi. It blows cool, but not cold. It's unusual how the low side now stays at like 60 psi and doesn't go up or down, even when the compressor comes on/off. Clogged orifice tube? The high side definitely goes up/down though.
Ran it for at least 30 min today, but couldn't get any water out of the evap drain. Maybe because it's not working efficiently? I assume this is linked to the low side not changing pressure?

Checked everything under the hood, no huge drooling UV dye streams. Seemed to be excessive UV dye in the high side port. I'm thinking maybe a Shrader valve in there is leaking?
 
Grandpa series... Orifise tube. 60 psi in low side implies not a big enough restriction or very overcharged. Should be seeing 300+ in high side if overcharged. Radiator fan needs to be moving air as part of this. High side pressures go up fast if that heat doesn't get out. Use 'tropical' fan clutch. You'll hear the fan. If using electric fan it gets triggered with compressor operation.

OP have you found the leak?
 
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