PolarGlade

Hey everyone,

So I put a vacuum pump on my R12 system last week to check for leaks before filling with refrigerant. It sat for 45 min and didn't budge on the gauges. After filling, it worked great for about two days, but it seems a leak has let the pressure drop to almost nothing.

So rather than using more expensive R12 and dye to find this leak, does anyone have any other suggestions?

PolarGlade

I was also thinking about pumping it full of Enviro-Safe substitute until I get everything worked out. Any thoughts on that idea?

CraigL

If you haven't already, you should find a micron-scale vacuum gauge.
It is much more sensitive than the gauges on the manifold.
If you can pull a 500 micron vacuum and maintain it, you should be good to go for recharge.
Another nice piece of equipment is a scale.
That way you can recharge the system based on refrigerant weight.

I'm sure others will chime in.

dr bob

Vacuum draws the AC connections tighter, so the 'holds vacuum' test is only a macro test for leaks.

If your car still has all the original seals/o-rings, do yourself a favor and just replace them all now. The originals are crispy and torn at their age, and nothing will cause them to seal again short of replacement. Our favroite suppliers have a kit of o-rings that will get you everything you need. Lubricate them properly as you install them, and don't tighten a hose connection until both ends are at least snug. That eliminates tearing/twisting of the seals. Also go gentle on the connecting nuts. As tempting as it is to pull hard on those big hex nuts, the torque required for sealing is a lot less. They need to not rock or anything, but you don't want to squish the o-ring to the point where it leaks. Make sure you seal at least the manifold plates on the compressor too.

Perhaps before you vent or recover the system, use an electronic sniffer to find leaks that aren't at the o-rings. Particularly, look at the compressor shaft seal area. Wrap a bit of Saran wrap around the pulley and the front of the compressor, and put the sniffer probe in the wrap. Even with low pressure in the system, you'll know in a minute or two if the compressor shaft seal is leaking.

The dye and UV light method works great if everything is clean and every connection and component is visible as you search. For most 928's, the first does not apply. For all 928's, the second does not apply.

------

There is no single magic bullet for old leaking systems. Invest the time and effort now getting everything you can up to snuff, and stand a chance of keeping the system going for another year. Or... Stock up on truckloads of R-12, and hope it's enough to keep you going for a few summers.

Don Carter

The trick I learned from the DFW crew was to fill the system with about 100psi of nitrogen, then spray soapy water on all the connections, the expansion valves, or any crimp connections on the rubber hoses and look for bubbles. It worked so well, I bought a tank of nitrogen and a regulator and I've used the approach several times since on my R12 systems. Sometimes you can even hear the leak.

Also, I have a Harbor Freight electronic freon sniffer that works very well.

PolarGlade

Thanks guys. I do have one advantage. I do hear a very, very faint hiss that sounds a bit like a sizzle, coming from what seems to be the inlet of the condenser. There are quite a few connections in that area so maybe one more try with R12 and dye. I suppose using up one can to find a leak is worth it.

OTR18WHEELER

before you open the system, make sure the compressor seal behind the pullys is not leaking.

SeanR

Don's right, find someone that can put some nitrogen in the system and go hunting. If you can hear a hiss, those bubbles will be easy to find. Most often I've found the leaks at the top of the compressor and the main suction/pressure hoses. I usually start there and work my way around the car. The biggest pain in the **** is the line that comes from the expansion valve all the way to the condenser, usually hidden behind either the ignition computer on early cars and the coil on the later cars under the 14 pin connector.

I'd not heard Dr. Bobs idea about saran wrap on the compressor.......neat idea and so simple. Thanks for that.

bureau13

I do think Dr. Bob's advice to just replace all the o-rings right now is good. You may be hearing the biggest leak, and you may find it with some dye, but if you don't replace those o-rings, you'll likely have other, smaller leaks that will prevent your system from working properly.

AirtekHVAC

Late to the party as usual....nitrogen, trace gas, soap bubbles....don't like the dyes.....

The refrigerant system is a pristine environment, some of us in the trade, especially the old school (of which I am) , do not believe in contaminating this pristine environment with foreign material. Not looking for a debate.

Add a little r22 vapor, a couple pounds of pressure will do, add nitrogen up to app 100# (start with 50)... Then use an electronic leak detector. You can try nitrogen alone, if you don't have an electronic, and use soap bubbles as above.

Good luck. If you were close, I'd do it for you, but I'm a giver......

SeanR

Novice asking here.

I've got a Snap-on and some generic brand detector and neither of them pick up leaks worth a damn. What do you recommend for those of us who do this on a frequent basis? I've resorted to just using the nitrogen/soap bubbles as the detectors I have don't work unless there is a 50psi stream coming from the leak.

Both of my electrical units seem to work fine for home HVAC leaks but not auto.........which makes no sense to me.

PolarGlade

Whew! OK everyone, I think I found the culprit.

The high side hose that connects to the inlet of the condenser that passes next to the frame, past the side of the radiator, then on down to the compressor is where the hiss is coming from. It's not the connectors though. It looks like that hose is really pinched between the radiator and the frame.

That thing looks buried in there. What do I have to pull to get that thing out?

SeanR

There are two hoses that pass in that area so make sure which one it is. One is easy once you remove the compressor. The other is a bitch and is not one you can easily remove from the car with the engine in.

PolarGlade

This one.

PolarGlade

This where it squeezes past the radiator. There is a gap above that it is not using. (the frame is the red in the pic) As if the shroud or bracket was put in without the hose being positioned properly.