A/C Leak Detection method recommendations?

mthomas58 · 01-18-2010, 10:50 AM

Background: Total system replaced 4/08. New barrier hoses, new compressor, new evap, new consensers (4 including Duehl Kuehl), Pro Cooler, high low cutoff switch.....i.e. every component has been replaced.

Although I'm not running the A/C this time of year I have noticed that last month or two that I could not get the A/C compressor to kick on and thought maybe it was the cold/ low pressure switch that would not allow it to kick on. Today I bypassed the H/L pressure switch and by doing so was able to get the compressor to cycle on and off regularly. Ran system and it did not cool at all so I must have a leak and am low on R-134a.

Recommendations on leak tracing? I don't have a sniffer but may need to get one.
I need to get the car up on a rack to visually inspect all the hoses, but assuming it passes the visual inspection, what is the best way to trace a leak?

I have not hooked up the gauges yet - What's the point? I already know I'm low and the system is not cooling.

Suggestions?

ShakinJoe · 01-18-2010, 10:58 AM

Rubber hoses leak....period. A good sniffer is going to set you back several hundred dollars. Some people put dye in the systems, but I do not like that.

My solution. Keep adding. R-134a is cheap.

tomphot · 01-18-2010, 11:01 AM

Let me know when you want to run over to get the car up in air.

Goth · 01-18-2010, 12:58 PM

Look for a wet spot. Usually at a connection or seal. If it's wet with oil; it's leaking.

Porschedr. · 01-18-2010, 03:04 PM

uv light and yellow glasses

mthomas58 · 01-18-2010, 03:24 PM

Quote:

Originally Posted by Geno911

uv light and yellow glasses

I'm not wild about the idea of using dyes as I have read that they tend to contaminate A/C systems.

rusnak · 01-18-2010, 03:45 PM

Look at it this way....you almost made it two years. You can do another vacuum and recharge and be good for another two years.

T77911S · 01-18-2010, 04:22 PM

put gages on to confirm you are low on 134. if it is low, check all the connections first look for the wet spot. make sure they are tight, if the 134 is all gone, go ahead and replace all the o rings. ,

James Brown · James Brown's Garage

you can get a adapter for a propane torch that has a rubber hose attached to it and you trace the a/c lines. If there is a leak, the flame changes color. There cheap and if you have a torch (burner if your British) then you just need a adapter. Check at any a/c repair shop (home, industral, commercal, or automotive).

Porschedr. · 01-18-2010, 05:35 PM

Quote:

Originally Posted by mthomas58

I'm not wild about the idea of using dyes as I have read that they tend to contaminate A/C systems.

Yet some manufactures have it in initially?
I've heard a lot of things too.

Tigerrat · Tigerrat's Garage

I haven't heard of an issue w/ dyes but with some of the stop-leak type stuff included w/ some refill cans. That said, my experience with using a dye was a pain cause it was so messy getting it in the system. Meaning, if there was a leak around the compressor and valve, I'd never have found it. The first place I would look would be the valves, especially if you used the adapter types on top of existing Schrader valves. That's where my leak was. Used some soapy water. Remember the caps are integral to a complete seal. Good luck.

Jetjockey · 01-19-2010, 06:17 AM

I used the dye and it shows leaks well. I also have a strong black light flashlight to loan if you need it. That is a disappointment to only hold the charge a couple of years with all new components. I would suspect the Nippondenso compressor first. Do you have an obvious oily line on the decklid above the compressor? My system showed a bad connection at the dryer and another at a service port where I installed the trinary switch. Two years is not that unreasonable to do a vacuum and recharge since you have all the equipment. That would be the case if it is a slow leak that has been happening for 2 years. On the other hand if it is a fast leak that has happened over a week, that would be a problem.

steve911T · 01-19-2010, 07:25 AM

I used the dye also and found the leak was the compressor, coming from the actual body of the compressor where it was bolted together. Hopefully Sam's will sell the 12 pack of the 134 for 35$ again and I will be back in business. The dye actually worked well and could not find any other leaks except that one and it is a slow leak. Good luck!

uwanna · 01-19-2010, 07:56 AM

Hi Mark,
I'm the guy with the '80SC 3.6 gray metallic thats close to your car color. We've chatted several times at the Avenues Sunday cruise in.
If you haven't found your leak by the next Avenues meet up, I can bring my "sniffer" for you use to try find your leak. Let me know.
Grant

JFairman · 01-19-2010, 08:03 AM

With slow leak like that there's no reason to re-evacuate it. It's not like air and moisture is gonna leak into it, the refrigerant is just leaking out untill pressure gets low enough and it stops so all you have to do is recharge it.

You only have to evacuate it if the system is opened up to atmosphere and then air and humidity gets in and replaces the refrigerant.

Oil will settle to the bottom areas of the hoses and heat exchangers from gravity so if the slow leak is near the top it won't be wet from oil.

I re did my entire AC system with all new rennaire and zims updated parts and barrier hoses that came to around 2 grand not including my labor.
It leaks down real slowly too, probably an oring somewhere fun to get at like in the smuggler box which is hard to open up with a strut bar in place..

I buy R134a at around $100 for a 30 lb botttle to maintain both my cars here in hot florida so it's really easy to just recharge it once or twice a year.

Mike Andrew · 01-19-2010, 09:08 AM

Mark;
Same issue with my Rennaire/Griffiths. Laeked down last winter and was fine when I stored the car. HVAC buddy & I pushed 170# of Nitrogen & pulled a vacuum for almost 2 hours. No leak at 85 ambient. Dyed it and recharged it and I WILL find that damn leak now taht winter is here. I suspect an O ring or fitting. $2000.00 & problems! ARRRGGGGHHHH!!!!!!

mthomas58 · 07:46 PM

All good comments. Thanks guys!

Quote:

Originally Posted by Jetjockey

I used the dye and it shows leaks well. I would suspect the Nippondenso compressor first. Do you have an obvious oily line on the decklid above the compressor? My system showed a bad connection at the dryer and another at a service port where I installed the trinary switch. Two years is not that unreasonable to do a vacuum and recharge since you have all the equipment. That would be the case if it is a slow leak that has been happening for 2 years. On the other hand if it is a fast leak that has happened over a week, that would be a problem.

I do unfortunatley have a little tell tale oil streak coming from the compressor clutch that I noticed shortly after the install. It is a Nippondenso Factory Rebuilt unit......I think when head temps get really high in peak season this happens to most compressors - at least the Nippo's. Griffiths states that Nippos are larger capacity units vs the Sanden replacements and are slightly better for our cars if they are working properly (Charlie - sorry if I'm miss-interpreting your comment but that was my understanding)....anyway that's why I stayed with the Nippo.

Quote:

Originally Posted by uwanna

Hi Mark,
If you haven't found your leak by the next Avenues meet up, I can bring my "sniffer" for you use to try find your leak. Let me know.
Grant

May take you up on your offer. I'll PM you the next time I plan on going. Ever get your hose connections re-done?

Quote:

Originally Posted by JFairman

With slow leak like that there's no reason to re-evacuate it. It's not like air and moisture is gonna leak into it, the refrigerant is just leaking out untill pressure gets low enough and it stops so all you have to do is recharge it.

You only have to evacuate it if the system is opened up to atmosphere and then air and humidity gets in and replaces the refrigerant.

Oil will settle to the bottom areas of the hoses and heat exchangers from gravity so if the slow leak is near the top it won't be wet from oil.

I re did my entire AC system with all new rennaire and zims updated parts and barrier hoses that came to around 2 grand not including my labor.
It leaks down real slowly too, probably an oring somewhere fun to get at like in the smuggler box which is hard to open up with a strut bar in place..

I buy R134a at around $100 for a 30 lb botttle to maintain both my cars here in hot florida so it's really easy to just recharge it once or twice a year.

Good to hear from several that slow leak downs with new systems are not uncommon. Since I've got all the equip, I'd perfer to evac and recharge so that I know how much 134a I've got in there. After several recharges, I've calibrated my "optimum charge" using a 30lb jug and a scale at 39 oz. If I just top off/ recharge, I'll have no idea where I'm at.

Quote:

Originally Posted by Mike Andrew

Mark;
Same issue with my Rennaire/Griffiths. Laeked down last winter and was fine when I stored the car. HVAC buddy & I pushed 170# of Nitrogen & pulled a vacuum for almost 2 hours. No leak at 85 ambient. Dyed it and recharged it and I WILL find that damn leak now taht winter is here. I suspect an O ring or fitting. $2000.00 & problems! ARRRGGGGHHHH!!!!!!

Let me know what you find? I plan on sniffing mine when I get it charged back up.

JFairman · 01-19-2010, 03:19 PM

"Good to hear from several that slow leak downs with new systems are not uncommon. Since I've got all the equip, I'd perfer to evac and recharge so that I know how much 134a I've got in there. After several recharges, I've calibrated my "optimum charge" using a 30lb jug and a scale at 39 oz. If I just top off/ recharge, I'll have no idea where I'm at."

With this formula from "KUEHL" I know exactly where I'm at and I can just top it off perfectly once or twice a year in a few minutes without wasting any R134.

These pressures are at idle speed with the lid down or if you have a fan(s) on the condensor(s) the lid can be up.

80-85F = ambient times 2.4 X 1.05 or the + 5% rule
86-90F = (ambient times 2.4) X 1.1 or the +10% rule
91-95F = ambient times 2.4 X 1.13 or the +13% rule
96-100F = ambient times 2.4 X 1.15 or the +15% rule
101-105 = ambient times 2.4 X 1.17 or the +17% rule
106-110 = ambient times 2.4 X 1.20 or the + 20% rule

"Here is how you apply the rules:
Say you have charged the system with a known quantity of R134a refrigerant (grams or ounces or whatever) and the ambient temperature is 95F. Take 95 and multiply it by 2.4 = 228 psi and then multiply that by 1.13 = 258 psi. Now consider if you really had this pressure well that would be in a perfect world. Depending upon whether you parked on black asphalt or if the expansion valve was opening or closing this mean target of 258 might swing up to 270 or so and frankly that is pretty good in a 911 with R134a at 95F. Or, if you are testing with the deck lid down and your services hoses are holding the deck lid up an inch or two that would reduce the effective air flow across the deck lid condenser and drive pressures upward. "

billybek · billybek's Garage

If it is flat (zero pressure) just find a regulator and charge the system with nitrogen as mentioned before. There should be enough residual gas in the system to provide a "trace" of refrigerant after nitrogenizing. Use the electronic leak detector and see what you can find.
You can always use a soap solution to leak check fittings while pressurized too...

rusnak · 01-20-2010, 01:56 PM

I usually top the charge up once or maybe twice before doing a full evac and pull a fresh vacuum. I just don't know how much water is in there, so I don't really like to just top it up, a personal choice/ quirk/ eccentricity or whatever. Besides, JFairman convinced me to buy the Robinair 6CFM 2-stage vacuum pump a few years ago, and I love using that thing.