AC / Testing for system leaks question?

rooster · June 23, 2007, 01:37:07 PM

I would like to check the AC system in my pickup for leaks, it was suggested to use
Nitrogen for the charge and a leak detector.

Is it nessary to first vacuum the system out to add Nitrogen for the leak test?

Is it possible to check for leaks by just placing a vacuum on the system and watching the
gauge on the manifold gauge set? I understand that this would not let me know where it
is leaking but would let me know how much or how fast it is leaking!

EMSjunkie · June 23, 2007, 01:51:47 PM

Quote from: "rooster"I would like to check the AC system in my pickup for leaks, it was suggested to use
Nitrogen for the charge and a leak detector.

Is it nessary to first vacuum the system out to add Nitrogen for the leak test?

Is it possible to check for leaks by just placing a vacuum on the system and watching the
gauge on the manifold gauge set? I understand that this would not let me know where it
is leaking but would let me know how much or how fast it is leaking!

Hey Denny, how you been??

what I did on my system was.....I just pulled a vacuum, about 30 mmhg, and let it set for about 30-45 min. and watching the gauge. found a pretty good leak, the vacuum only lasted about 10 min. :x

good luck

Vance

rooster · June 23, 2007, 02:22:38 PM

I have been doing ok! Just a few more weeks of work to do and its back to retirement.

In the area where your leak was, was it oily looking? I would guess that found the leak area, repaired it, and then did the vacume again or did Nitrogen test.

GPster · June 23, 2007, 02:46:12 PM

The leak detectors that I'm familiar with are mostly for refrigerant and won't see Nitrogen. If you have a positive pressure of regrigerant on the system and add nitrogen the additional pressure might make it easier to find a leak but I would plan a vaccum after adding the nitrogen and fixing the leak. Pulling a vacuum first is only going to suck-in/contaminate the system with air and would only make the process harder. To be able to find the leak, that is more than likely on the low-pressure/suction side of the system you shouldn't need much pressure. If the leak is on the High-pressure side of the system it is usually found by an oil leak becuse the compressor will usually suck it's oil out of it's crankcase and put it at the leak. Remember the compressor is usually the low-pressure side of the system and you don't need that much pressure to check the seal and they usually leak when they're not running. Keep asking questions as I can't remember all the answers. GPster

Ed ke6bnl · June 24, 2007, 10:20:04 AM

Nitrogen is good but must be mixed with a few oz. of refrigerant. Can put in 125 psi if you like. they make inexpensive propane leak detectors that work well they heat a small copper plate and the refrigerant will cause the blue flame to turn green at a leak. They do have dyes that will glow with a black light at the leak that are mixed with the oil. the system will still need to be bled and evacuated and charge best by weight. Good luck Ed ke6bnl

enjenjo · June 24, 2007, 04:22:34 PM

The leak detector we used heard the leak, it was a sonic detector, so we could use straight nitrogen.

You can not correctly charge R134 with a sight glass, that's why most new cars don't have one.

rooster · July 04, 2007, 03:09:34 PM

Quote from: "enjenjo"The leak detector we used heard the leak, it was a sonic detector, so we could use straight nitrogen.

You can not correctly charge R134 with a sight glass, that's why most new cars don't have one.

Doing some snooping around at the parts store I found a small can of 134a that has uv leak detector dye in it ( 2.5 oz of 134a an 2.5 oz of oil with dye in it).

Question: would the oil with the dye in it harm the new gauge set I got from HF, if I add it to the system to find leaks?

The dye can plugs directely into the low side of the system with the engine running and ac on.

Fat Cat · July 04, 2007, 06:22:54 PM

Quote from: "rooster"
Quote from: "enjenjo"The leak detector we used heard the leak, it was a sonic detector, so we could use straight nitrogen.

You can not correctly charge R134 with a sight glass, that's why most new cars don't have one.

Doing some snooping around at the parts store I found a small can of 134a that has uv leak detector dye in it ( 2.5 oz of 134a an 2.5 oz of oil with dye in it).

Question: would the oil with the dye in it harm the new gauge set I got from HF, if I add it to the system to find leaks?

The dye can plugs directely into the low side of the system with the engine running and ac on.

To use that dye charge properly your going to need the system up and working to add it to the system. Which means your going to need at least 1.7-3.2 lbs of refrigerant(depending on the needs of your specific vehicle) in the system. When the system is working properly you can add the dye charge to the system. Run it for at least 20-30 minutes. Then you can inspect it for leaks with a UV light.

Putting 2.5 ounces of freon into a empty system will not be enough to make the compressor come on. You also need to evacuate all the moisture out of the system before adding any dye or oil. The oil will not hurt the gauge set.

rooster · July 07, 2007, 01:28:52 PM

I hooked a vacume pump up to the system, turned the pump on and within 5 seconds it pumped the system down to 1 bar! Is this normal to happen this fast?

Plans are to add 134 until compressor get going, then add dye, then drive it around for awhile and check with the uv light for leaks also have the eletronic sniffer.

This is on the 95 GMC truck 1500. The lable says it takes 2 pounds of 134.

GPster · July 07, 2007, 04:24:55 PM

Quote from: "rooster"I hooked a vacume pump up to the system, turned the pump on and within 5 seconds it pumped the system down to 1 bar! Is this normal to happen this fast? A better indication as to how bad the leak may be would be to close the valve between the gauge and the pump so you can turn off the pump and watch how fast the system looses it's vacuum.

Plans are to add 134 until compressor get going, You're going to get the system where it will cycle on the "Low Pressure Switch". You might only add enough refrigerant to make the switch when it's pressures are neutralized but when the compressor starts it will draw the low side down and be shut off by the swithc, You won't have to use 2 lbs. but you will need more than enough to re-set theswitch. then add dye, then drive it around for awhile and check with the uv light for leaks also have the eletronic sniffer.

This is on the 95 GMC truck 1500. The lable says it takes 2 pounds of 134.

rooster · July 07, 2007, 05:33:46 PM

Quote from: "GPster"
Quote from: "rooster"I hooked a vacume pump up to the system, turned the pump on and within 5 seconds it pumped the system down to 1 bar! Is this normal to happen this fast? A better indication as to how bad the leak may be would be to close the valve between the gauge and the pump so you can turn off the pump and watch how fast the system looses it's vacuum.

Plans are to add 134 until compressor get going, You're going to get the system where it will cycle on the "Low Pressure Switch". You might only add enough refrigerant to make the switch when it's pressures are neutralized but when the compressor starts it will draw the low side down and be shut off by the swithc, You won't have to use 2 lbs. but you will need more than enough to re-set theswitch. then add dye, then drive it around for awhile and check with the uv light for leaks also have the eletronic sniffer.

This is on the 95 GMC truck 1500. The lable says it takes 2 pounds of 134.

I ran the vacume pump for additional 1/2 hour, then waited with the gauges shut off to watch the reading, 3 hours later there was some movement in the gauge. not much though!

I then added 1 can (12 oz) of 134, the compressor came on and short cycled for awhile then stayed on, I added a squirt of dye, I could see that along the front side of compressor along its outter edge oil leaking around its case. Also noticed that after removing dye can both port in the system that they leaked.

The gauges read 32 low side an 0 high side with 1 can added. I guess this means the compressor is shot.

Will do daugthers Mustang tommoro

rooster · July 07, 2007, 05:35:51 PM

Quote from: "GPster"
Quote from: "rooster"I hooked a vacume pump up to the system, turned the pump on and within 5 seconds it pumped the system down to 1 bar! Is this normal to happen this fast? A better indication as to how bad the leak may be would be to close the valve between the gauge and the pump so you can turn off the pump and watch how fast the system looses it's vacuum.

Plans are to add 134 until compressor get going, You're going to get the system where it will cycle on the "Low Pressure Switch". You might only add enough refrigerant to make the switch when it's pressures are neutralized but when the compressor starts it will draw the low side down and be shut off by the swithc, You won't have to use 2 lbs. but you will need more than enough to re-set theswitch. then add dye, then drive it around for awhile and check with the uv light for leaks also have the eletronic sniffer.

This is on the 95 GMC truck 1500. The lable says it takes 2 pounds of 134.

I ran the vacume pump for additional 1/2 hour, then waited with the gauges shut off to watch the reading, 3 hours later there was some movement in the gauge. not much though!

I then added 1 can (12 oz) of 134, the compressor came on and short cycled for awhile then stayed on, I added a squirt of dye, I could see that along the front side of compressor along its outter edge oil leaking around its case. Also noticed that after removing dye can both port in the system that they leaked.

The gauges read 32 low side an 0 high side with 1 can added. I guess this means the compressor is shot.

Will do daugthers Mustang tommoro

rooster · July 09, 2007, 09:07:21 AM

I charged the Mustang system yesterday, this time it took about a can a half for the compressor to stay on, went ahead an put both cans in then gave it a shot of dye also. air is cold , will take a look tonight with the uv light to see if our junkyard compressor is a leaker or not. It still needs a few more oz's to be full by weight, I suppose I will have to guesstmate that if no leaks are found. Mustang has another issue of having only air coming out of defrost ducts, it wont move from this position.

2 down 1 to go!
Jr's car is next 94 olds cutless.