I'm about to go on a leak hunt in my AC system, was wondering if the following triggered any memories or experience from anybody?

- AC system was holding a little bit of static pressure (10lbs or less)
- pulled a vacuum on the system and it held for 20 minutes (which I normally associate with no leaks...)
- filled system with refrigerant, and it worked beautifully. Compressor was cycling, inside air was nice and cold, pressures on high and low side were good.
- come back next day, and back to 10lbs of pressure.

So what puzzles me is that it held a vacuum, but had a pretty serious leak.

Anybody seen this before, and if so, remember what the cause was?

I'm just trying to get as much info as possible to start in the best place.

Thanks!

you probubley have a pin hole for a leak. I beleave they sell ac UV dye, but you will need a UV light too. Just a wild guess a small stone hit the ac....dang whats that called, the radiator for the ac? sits if front of the fiero radiator. you will also want to replace the O-ring ac washers.

[This message has been edited by James Bond 007 (edited 04-11-2017).]

quote Originally posted by James Bond 007: Just a wild guess a small stone hit the ac....dang whats that called, the radiator for the ac? sits if front of the fiero radiator.

Condenser!

UV Dye is your friend...

There's always a bit of refrigerant floating around in there, even when 'empty' hence the small amount of pressure.
Air molecules are much bigger than refrigerant molecules so while refrigerant molecules may get out, air may not get in.
Also, when filled with refrigerant the static pressure is around 80/90 lbs, when running, high side is 200 ish I think vs the 14 psi you get by pulling a vacuum.
So basically, pulling a vacuum, especially for such a short time, proves very little.
The only reason to pull a vacuum is to get all the moisture and air out of there before you fill it.

Dye is good except for detecting a leaking schrader valve because that's where the dye goes in (with the oil) so there's bound to be dye around that port.
Iv'e got a super sensitive microphone (forget the make) to try and find the leak by listening for it. Still not got around to trying it though yet. maybe this will be the year!

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Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

www.ltlfrari.com

Thanks guys. The charge did have a dye in it, so I'll go looking for it. I'm hoping it will be obvious. Good input on the valve. It certainly has dye around it, but that's to be expected from the filling.

Start under the car at the hard lines, then the compressor shaft seal, any hose joints, and any line connections. After the usual suspects, just follow the lines around the car. Yes this will require crawling under it, unless you have a lift.

I'm in this same situation. This is almost the exact question I was going to ask, so I hate to start another thread. My system has a leak, and I need to find it & fix it. First, I assume this is talking about an R134 system. Mine has been converted. 2nd, where do I get UV dye? And 3rd... where do I get a UV light that won't break the bank?

Any part store will have or can get UV dye and light. Light come many forms from a pin light, a light that has wires to attach to the battery, to expensive ones

quote Originally posted by Formula Owner: I'm in this same situation. This is almost the exact question I was going to ask, so I hate to start another thread. My system has a leak, and I need to find it & fix it. First, I assume this is talking about an R134 system. Mine has been converted. 2nd, where do I get UV dye? And 3rd... where do I get a UV light that won't break the bank?

LEDs have made UV lights CHEAP on Amazon.

Example
.

I am about to go on this hunt myself..Once I find the leak, then what?

quote Originally posted by Threedog: LEDs have made UV lights CHEAP on Amazon. Example

Thanks for the link. I was hoping something like that, in that price range, was available.

quote Originally posted by Threedog: I am about to go on this hunt myself..Once I find the leak, then what?

Um, replace the leaking item? If it's leaking at a joint, it's likely a seal that's leaking. If the leak is on the condenser, evaporator, or compressor, then that's what needs replacing. I sure hope mine's just a leaking seal. Or maybe one of the valves on the hi & lo ports.

quote Originally posted by Formula Owner: Um, replace the leaking item? If it's leaking at a joint, it's likely a seal that's leaking. If the leak is on the condenser, evaporator, or compressor, then that's what needs replacing. I sure hope mine's just a leaking seal. Or maybe one of the valves on the hi & lo ports.

The only things that are not new on my system are the lines from front to back, and the accumulator(thing in front of the radiator?), both which can't really be replaced..

quote Originally posted by Threedog: The only things that are not new on my system are the lines from front to back, and the accumulator(thing in front of the radiator?), both which can't really be replaced..

Why can't they be replaced? No longer available? If so, that would suck.

Back to the topic... How does one go about finding a leak? Put in one can of R134 w/UV dye? Two? Three? One can w/dye, and then fill with non-dyed R134? I wouldn't want to fill my system, as it will just leak out. I would like to waste the minimum amount of R134.

quote Originally posted by Formula Owner: Back to the topic... How does one go about finding a leak? Put in one can of R134 w/UV dye? Two? Three? One can w/dye, and then fill with non-dyed R134? I wouldn't want to fill my system, as it will just leak out. I would like to waste the minimum amount of R134.

One way is to pressurize the system with Nitrogen, and then listen ( or use soapy water in a spray bottle) to hunt for leaks. I don't have nitrogen, so I use clean dry shop air, to about 80 PSI. Once I find and fix the leak, I'm sure to pull a very good vacuum ( 1-2 hrs total) to make sure no water is left in the system. I also use Dye, but that does require charging the system with a couple of cans of R134a ( at least one with dye), and the leak is not always visible ( found one at the top of the condenser, where it had worn through due to vibration).

Accumulator is the can thing in the front bay.
Thing in front of radiator is condenser because it uses the air flowing over it to condense the expanded gas back into a liquid.
Both items are available and can be replaced although the condenser is a bit of a sod to do, it's just squeezed in there really tight and you'll probably need new 'well nuts' for the bottom mount (took me forever to find out what those nuts in a rubber case are called).

------------------
Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

www.ltlfrari.com

I have a 3800 swaped fiero with the compressor off the donor car, how do I find out what the high and low readings should be?

If the dye does not show anything, I have had better luck putting pressure on the system, looking for leaks with soap bubbles. If you have nitrogen, great, if you have a MIG welder, use the MIG mix, filtered shop air if you have to - just use one of the inline paint filters. Put 100 psi on it, then go looking. Easy for a weld or crimp to leak under pressure, suck closed under vacuum. Don't forget the joint under the front tub, kinda under the master cylinder.

Mike

I notice that the leak kits have a black light and a pair of yellow glasses. Do these glasses have some kind of special yellow filter? Or will any yellow glasses work? I have some yellow glasses from when I used to ride mountain bikes.

quote Originally posted by airwrench: ... So what puzzles me is that it held a vacuum, but had a pretty serious leak. ...

Mine held a vacuum for 24 hours, and still had a slow leak.

quote Originally posted by vette7584: I have a 3800 swaped fiero with the compressor off the donor car, how do I find out what the high and low readings should be? ...

The readings are not specific to any engine or car. They're specific to the type of refrigerant, and the ambient temperature. I'm guessing R134.

I had a leak in my ford explorer that I couldn't find so I bought a leak detector from Harbor Freight.
Found the leak under the condenser that I couldn't see or access very easily. Worth the money in time saved.

https://www.harborfreight.c...-detector-92514.html

[This message has been edited by Nextel dude (edited 05-07-2017).]