Where did my AC system leak?

[987687]

I have a 98LGT with 228k miles on it. Only problem with it now is the AC doesn't work. The compressor won't even engage. Tried with defrost, heat on coldest setting with AC button, etc. It will not come on. So I checked the system pressure, and there's no pressure. I guess there's a pressure switch disabling the system? Will recharging the system fix that?

 

Also, since there's no pressure I'm not gonna recharge until the leak is fixed. Where do these usually leak? It will be easy to work on now that it's all leaked out...

[davebugs]

O rings at the hoses are common.

 

But I believe their are some AC experts here that'll know a lot more than me.

 

I take my AC issues to a real AC guy. I learned long ago - just like exhaust pipe repair that it just wasn't worth the correct tools and developing the knowledge for me to fix AC.

 

Is your condensor o.k.? Any front end damage? SImply follow the trail of the gas.

[NorthWet]

I would agree that, in the end, it is best to let an AC guy fix, evacuate and recharge the system. That being said...

 

The AC system contains both refrigerant and lubricating oil. Usually whenever you get a gas leak some of the oil will also leak out, leaving oily residue around the leak site. Check all of the fittings (leaking o-rings), the condenser (for cracks and FOD damage), hoses for rub-throughs, and around the compressor drive-pulley (front and back) for a leaking front seal.

[987687]

I'll take a look. The old engine in this car was pretty blown. Oil and coolant ALL OVER THE PLACE. So I've done a bunch of cleaning. May be hard to see what came from AC and not.

 

Is the AC pump not coming on a separate issue? or is it smart enough not to come on with no pressure?

[davebugs]

Again the experts will know for sure.

 

But I believe on most AC systems if the charge is low the compressor knows not to come on.

 

My guy pulls a vacuum to make sure the system is "closed" before recharging. If it's charged and compressor gets signal and still doesn't run it's the compressor. They can also pur a dye in if it's a stubborn leak. Jsut like the dye for oil or coolant.

 

I've got a selection of used AC compressors here. They all bolt up the same but often the hoses are different. Luckily I have a selection of those as well. On the rare occasions I've had AC compressor issues having the combination of an AC compressor and it's matching hoses has given me more flexibility than buying a reman AC compressor. But I realize a lot of folks don't have the luxury of the parts stash that I have.

[Scoobywagon]

I'll preface this by saying that, as has been said, you should probably take this to an A/C expert to have it looked over. That said...

 

There are LOTS of places for an A/C system to leak. Everywhere there is a connection, there's at LEAST 1 o-ring and, in many cases, 2 or more. Look for oily residue on the hoses. Many A/C shops put dye in the system when they add refrigerant. I'm betting this isn't the first time that car has leaked, so there's a fair chance that there's some UV dye in there. You can either wait until late at night when its really dark out or pull it into a garage with the doors closed and all the lights out. Get yourself a UV light and look for the glowy bits.

 

Once you've done all that, it is still possible that you've not located your leak. R134a is corrosive in the presence of moisture. So it is possible that the, already thin, aluminum in the evaporator or condenser cores has become so thin that the refrigerant is leaking directly through the aluminum.

 

A professional is going to be able to assess that most efficiently.

[idosubaru]

a/c systems are really easy, i charge and fix them all the time without any special equipment. subaru's seem relatively easy to me, they don't typically have anything major or difficult to repair. orings and compressors are about the only things i've replaced - and one condensor.

 

yes, the system is intended to not operate if the pressures aren't proper so that's all normal.

 

the orings at the compressor are a common leak point - that's the point that sees the most heat, vibration, etc because they're right on top the engine.

 

there are also two schrader valves in each high and low pressure port. remove the caps and look down there, if you see signs of wetness that means either someone recently charged it or it's leaking. pull those and replace them while it's getting fixed. they have an oring at the base that can leak.

 

follow the A/C hoses off the compressor and you'll find orings at the other ends as well. do the same for the whole system, replacing any easy to get to fittings with new orings.

 

it's not that unusual to just replace a few orings you can access and fix the problem. it's worth a shot and it's so easy it doesn't take much time. t he only annoying part is not knowing what sizes they are, i just buy one of those huge packs of a/c orings and size them up as i go. it's getting thin, i need another one.

 

you can also just blow some charge in there with the system sealer stuff and hope it holds for the summer.

 

sounds like the engine was swapped - was the radiator removed? did the engine hit any a/c hoses or the front condensor?

 

if it was ever in an accident the condensor could be compromised.

[987687]

WOW! Thank you for all the great info Gary!

I'll source the o-rings and schrader valves for sure. Doesn't sound very hard to replace at all!! When I had the rad out the condenser looked fine, not bent, no messed up fins on either side, etc.

I cut a piece of plywood to protect the condenser so it wasn't damaged. All that came into contact with it was my knuckles

 

I'll also get a black light out there and see if theres an UV dye, great suggestion!

 

 

Thanks for all the advise guys. This is really awesome.

[Scoobywagon]

A few things to be aware of as you proceed.

 

First, if you are going to have the system open for any length of time, replace the receiver/drier while you're at it. Think of it as $30 worth of A/C insurance.

 

Secondly, and I think really more importantly, when it comes time to charge the system, you need a vacuum pump to do so properly. Yes, you can just 'blow some charge in there', but you'll still have air and air has moisture. As I said before, R134a is corrosive in the presence of moisture. The receiver/drier should take care of some of that, but really that just means you're shortening the life of your receiver/drier.

 

Third, any o-ring that you disturb should be replaced. That means that if you disassemble a fitting, replace all of its o-rings before you reassemble it, even if they look good.

 

This is why you need to try to figure out where its leaking first. It'll save you buying a bunch of o-rings you don't need, though its not like they're terribly expensive. And it'll save you a bunch of time working on things that don't need working on.

[djmark7]

i pulled my rad and mustve done something to the melal line coming off the condenser on the pass side at the bottom under the rad. petcock, check there i had to replace the metal line from the condenser to the dryer since then, all ok

[Allpar Mod]

The guys are giving you some sound advice. If you have no a/c experience and the proper tools, it's better to take it to an expert.

 

It could be several things like has been mentioned. O-rings are common. Schrader valves do go bad. I had one go bad on one of my Jeeps and until I found it, it was frustrating. Leaks at the condensor (sits in front of the radiator) are common on older vehicles.

 

You either need the UV light and dye in the system or a halogen detector to pinpoint the leak. I have both and like the halogen detector better, though it is much more expensive (fell into a used Snap On detector at a flea market). You need to recharge the system to find a leak, so if you don't know how to tell where the leak is or how to repair it after it's found, you're throwing money away for the freon to find the leak in the first place. Also, for recharging, home DIYers often make the mistake of not getting a pressure gauge when they get the DIY kits. Overcharging an a/c system often results in blowing out the o-rings or other seals. Many systems will work with some degree of overcharging, some won't. Either way, it's not good.