[IntrepidLover1956]

After replacing everything on my A/C system (except for the evaporator) with new parts, I pulled a vacuum for about an hour and a half down to nearly -30 psi. I then let it sit for another 3 hours to see if it lost any vacuum. It didn't budge. I thought I was set so I filled it with the specified amount of refrigerant. The air blew really cold, and I was really enjoying it. The next day, no more cold air. Obviously, there is a leak. Under vacuum, no leak. Under pressure, refrigerant leaks. Which leaves me with the following questions:

1. After finding and fixing the leak, I will vacuum again and recharge. Will this remove the PAG oil (I was under the impression that vacuuming wouldn't, but I've seen conflicting information)?

2. Presuming that vacuuming the system doesn't draw any of the PAG oil out of the system, would it have evaporated from being exposed to the outside air through the leak? I'm really not looking forward to removing the compressor, draining the oil, and then filling it with the proper amount; but I do not want a compressor failure either.

Any suggestions are appreciated, especially if there are other factors which I have failed to consider.

 

[NOLAdude]

Did you still have the gauges connected to it when you "let it sit" for 3 hours to see if it lost vacuum? If so, it's possible that your leak is at one of the Schrader valves. I've seen this same thing happen on a friend's truck. He could find no leaks and it even held vacuum overnight (with gauges attached) but after recharging it, it all leaked out within a day or so. Turned out to be bad Schrader valves. After he replaced them, all was good. So I would replace the Schrader valves and then check it again after that.

 

[peva]

If it was by slow leak, you probably didn't lose any significant amount of oil. The oil stays settled in low areas unless there is higher refrigerant flow.

 

[IntrepidLover1956]

Did you still have the gauges connected to it when you "let it sit" for 3 hours to see if it lost vacuum? If so, it's possible that your leak is at one of the Schrader valves. I've seen this same thing happen on a friend's truck. He could find no leaks and it even held vacuum overnight (with gauges attached) but after recharging it, it all leaked out within a day or so. Turned out to be bad Schrader valves. After he replaced them, all was good. So I would replace the Schrader valves and then check it again after that.

I went through that scenario last summer. Replaced both Schrader valves. I just vacuumed down the system earlier today and charged it with the specified amount of refrigerant (28 oz.). It dropped the vent temperature from 93.3 to 57.2. I purchased a "sniffer" a couple of weeks ago, and it didn't reveal any leaks. The only place I didn't get to check is the evaporator in the dash. Will have to wait and see if it leaks out again.

 

[LUNAT1C]

My system leaked for 6-7 years before I finally broke down and pulled the dash for evap replacement. It would always hold vacuum, but what started as being good for a couple years, ended up at months of leaking out. Pulling vacuum is great for finding large leaks, not so much small ones. It didn't even find the leak from having an improperly sized o-ring on my expansion valve, which I only found when the refrigerant sprayed all around it during charging. Pressurizing seems to be the more accurate route to go, but I'm not sure how to go about that without shop equipment. I believe CO2 is used to pressurize, but don't quote me on that.

Repeated evacuation, pulling vacuum, and continual leaking will result in some oil loss, but not enough to worry about. If you're replacing major components (evap, condenser, compressor), yes add the appropriate amount of oil. Concerning compressor, it was recommended to me to drain the old compressor and measure the amount of oil that was in it, then drain the new compressor (if it's pre-oiled) and replace with fresh oil of the same amount that was in the old one.

So, if you're replacing the evap, add the appropriate amount of oil for the evap. I can't remember what I added for the system in my Special a few years ago, half an ounce or one ounce. I'll need to do it again for the condenser since that sprung a leak last year.

I don't know how 1st gens are set up, but on 2nd gens the evap can be checked by removing the glove box closeout panel, glove box, and twisting out the thermistor cover to shine a UV light in (assuming the system was charged with dye). I found speckling of dye on the fins of my evap.

 

[IntrepidLover1956]

My system leaked for 6-7 years before I finally broke down and pulled the dash for evap replacement. It would always hold vacuum, but what started as being good for a couple years, ended up at months of leaking out. Pulling vacuum is great for finding large leaks, not so much small ones. It didn't even find the leak from having an improperly sized o-ring on my expansion valve, which I only found when the refrigerant sprayed all around it during charging. Pressurizing seems to be the more accurate route to go, but I'm not sure how to go about that without shop equipment. I believe CO2 is used to pressurize, but don't quote me on that.

Repeated evacuation, pulling vacuum, and continual leaking will result in some oil loss, but not enough to worry about. If you're replacing major components (evap, condenser, compressor), yes add the appropriate amount of oil. Concerning compressor, it was recommended to me to drain the old compressor and measure the amount of oil that was in it, then drain the new compressor (if it's pre-oiled) and replace with fresh oil of the same amount that was in the old one.

So, if you're replacing the evap, add the appropriate amount of oil for the evap. I can't remember what I added for the system in my Special a few years ago, half an ounce or one ounce. I'll need to do it again for the condenser since that sprung a leak last year.

I don't know how 1st gens are set up, but on 2nd gens the evap can be checked by removing the glove box closeout panel, glove box, and twisting out the thermistor cover to shine a UV light in (assuming the system was charged with dye). I found speckling of dye on the fins of my evap.

I haven't checked it since filling on Sunday. If it has leaked, the evap is about the only thing left to check. I just dread the thought of tearing out the dash.

 

[peva]

...Pressurizing seems to be the more accurate route to go, but I'm not sure how to go about that without shop equipment. I believe CO2 is used to pressurize, but don't quote me on that...

You may be thinking about dry nitrogen. It is inexpensive (you can rent small tanks of it from welding equipment and gas supliers (such as AR3). Purging and pressurizing the system with nitrogen for leak testing (before final pump down and recharging) has the very good side benefit of displacing moisture that may be trapped in the system - you end up with an order of magnitude less moisture in the system (moisture in the system is the enemy of a.c. performance and forms acids that can corrode metals in the system).

I keep a middle size bottle of nitrogen in my home garage for this purpose - to also use for filling and maintaining pressure in my tires.

 

[IntrepidLover1956]

You may be thinking about dry nitrogen. It is inexpensive (you can rent small tanks of it from welding equipment and gas supliers (such as AR3). Purging and pressurizing the system with nitrogen for leak testing (before final pump down and recharging) has the very good side benefit of displacing moisture that may be trapped in the system - you end up with an order of magnitude less moisture in the system (moisture in the system is the enemy of a.c. performance and forms acids that can corrode metals in the system).

I keep a middle size bottle of nitrogen in my home garage for this purpose - to also use for filling and maintaining pressure in my tires.

I've given a lot of thought to pressurizing the system to check for leaks, but I have no idea how to do it properly. Any chance you can guide me in the proper direction?

 

[peva]

I've given a lot of thought to pressurizing the system to check for leaks, but I have no idea how to do it properly. Any chance you can guide me in the proper direction?

After you pump it down and hold a vacuum for a few hours to "boil" off any moisture, you refill it, but with nitrogen to something like 80 psi. When you pull a hard vacuum again before charging with refrigerant, that will scavenge moisture in blind areas and from the oil (PAG oil is hygroscopic, meaning it likes to absorb and hold onto moisture). You could even fill and pressurize with nitrogen, pull a hard vacuum a second time, then let it sit under vacuum for a couple of hours (to boil off and pull any remaining moisture out of the oil), and then pressurize with nitrogen a second time, and let it sit for several hours to see if pressure drops.

I forget if the sniffers will detect nitrogen. Maybe not, but I never got the knack for using the sniffer to detect leaks with a charge of refrigerant - bought one and tried to use it, but never was successful pinpointing refrigerant leaks with it. Gave up on using a sniffer. They may be useful for that - just not tor me. So - basically, I use the pressure test with nitrogen to determine if there is a leak, but not to pinpoint where the leak is.

I always just make sure I have UV dye in the system, and look for leaks using a UV flashlight after system usage. If you can get a sniffer to pinpoint leaks and if it will detect nitrogen (and maybe they can't), then more power to you. You could use another gas that is a bit cheaper than refrigerant if the sniffer will defect it, but nitrogen is specifically used because of its ability to get more moisture out (it's very dry when you put it in so you're not introducing any additional moisture, and when you remove it, after the boiling off of liquid water under vacuum, it carries the moisture out with it.

Keep in mind that bottled gases are pressurized to a couple thousand psi, so you need to be sure to have a proper pressure regulator and gauge on the bottle and set it to less than 100 psi so you don't destroy your system or hurt yourself. 🙀

Whenever discharging, do it relatively slowly so whatever gas you're letting out, whether refrigerant or nitrogen or whatever, is not picking up and sweeping out your system oil.

If you open up your system to replace a component, consider replacing the receiver-dryer (to renew the desiccant) with a name-brand part. Make sure the port seals are not broken before you're ready to install it - if the seals are already broken when you buy it, refuse to accept it. (BTW - the receiver-dryers come filled with nitrogen to help keep the desiccant dry - that's why the intact seals are important.)

Why use nitrogen to purge moisture?

Terra offers a comprehensive range of application-specific desiccator cabinets and nitrogen control systems. These performance concepts will help you select the system right for your application.Nitrogen is the standard medium for contamination-free storage because it is relatively inert&m

www.terrauniversal.com

Moisture-Free Storage: Nitrogen or Desiccant?

Desiccators, sometimes called dry boxes, provide a low-humidity atmosphere for storage of items and materials that would otherwise be damaged by moisture. Desiccators are used for a wide range of applications across several scientific disciplines. In chemistry and biology, desiccators are often use

www.terrauniversal.com

 

[IntrepidLover1956]

After you pump it down and hold a vacuum for a few hours to "boil" off any moisture, you refill it, but with nitrogen to something like 80 psi. When you pull a hard vacuum again before charging with refrigerant, that will scavenge moisture in blind areas and from the oil (PAG oil is hygroscopic, meaning it likes to absorb and hold onto moisture). You could even fill and pressurize with nitrogen, pull a hard vacuum a second time, then let it sit under vacuum for a couple of hours (to boil off and pull any remaining moisture out of the oil), and then pressurize with nitrogen a second time, and let it sit for several hours to see if pressure drops.

I forget if the sniffers will detect nitrogen. Maybe not, but I never got the knack for using the sniffer to detect leaks with a charge of refrigerant - bought one and tried to use it, but never was successful pinpointing refrigerant leaks with it. Gave up on using a sniffer. They may be useful for that - just not tor me. So - basically, I use the pressure test with nitrogen to determine if there is a leak, but not to pinpoint where the leak is.

I always just make sure I have UV dye in the system, and look for leaks using a UV flashlight after system usage. If you can get a sniffer to pinpoint leaks and if it will detect nitrogen (and maybe they can't), then more power to you. You could use another gas that is a bit cheaper than refrigerant if the sniffer will defect it, but nitrogen is specifically used because of its ability to get more moisture out (it's very dry when you put it in so you're not introducing any additional moisture, and when you remove it, after the boiling off of liquid water under vacuum, it carries the moisture out with it.

Keep in mind that bottled gases are pressurized to a couple thousand psi, so you need to be sure to have a proper pressure regulator and gauge on the bottle and set it to less than 100 psi so you don't destroy your system or hurt yourself. 🙀

Whenever discharging, do it relatively slowly so whatever gas you're letting out, whether refrigerant or nitrogen or whatever, is not picking up and sweeping out your system oil.

If you open up your system to replace a component, consider replacing the receiver-dryer (to renew the desiccant) with a name-brand part. Make sure the port seals are not broken before you're ready to install it - if the seals are already broken when you buy it, refuse to accept it. (BTW - the receiver-dryers come filled with nitrogen to help keep the desiccant dry - that's why the intact seals are important.)

Why use nitrogen to purge moisture?

Terra offers a comprehensive range of application-specific desiccator cabinets and nitrogen control systems. These performance concepts will help you select the system right for your application.Nitrogen is the standard medium for contamination-free storage because it is relatively inert&m

www.terrauniversal.com

Moisture-Free Storage: Nitrogen or Desiccant?

Desiccators, sometimes called dry boxes, provide a low-humidity atmosphere for storage of items and materials that would otherwise be damaged by moisture. Desiccators are used for a wide range of applications across several scientific disciplines. In chemistry and biology, desiccators are often use

www.terrauniversal.com

Thanks for the detailed reply. I still need additional information about nitrogen gas:
1.) Where do you purchase it?
2.) What is its cost?
3.) What tool(s) do you use to pressurize the system with it?

I'm still hoping that I will find my system pressurized after the recharge on Saturday. I left the car at my sister's so I could borrow her Explorer for some hauling. Fingers crossed!

 

[Ronbo]

Nitrogen can be purchased at any welding supply store. You'll have to rent the bottle. I'm guessing it's around $50-75 for a small bottle these days.

 

[peva]

I get mine from Arc3 Gases (Locations and Contacts -), which appears to be regional to the east coast. The smallest bottle is 20 cu-ft, and is more than enough for anything you'd need to do on your car a.c. I was thinking it was around $16 for the nitrogen plus a small monthly fee until you return the bottle, empty or not. But that was 6 or 7 years ago. I bought a 20 cu-ft bottle for about $75 plus $16 or so for the nitrogen it contains. I traded the bottle in whenever I emptied it, and only paid for the nitrogen (again, under $20). As I started using it to till my tires (for example, when I buy a new set of tires, I empty them of air and fill with nitrogen), I needed a bigger bottle, so they took the 20 cu-ft bottle back in trade and gave me a 40 cu-ft bottle for the difference in price l between 20 and 40 cu-ft bottles. I think the price for a 40 was about $125 (plus the nitrogen). Price no doubt varies by region, and has gone up.

 

[EagleESI]

Evap cores are know for going bad. Honestly the dash is not the bad at taking out. Much easier if you remove the front seats and center console completely. Also best time to do heater core while in there!

Some photos of my 93 to give you an idea...

My wonderful heatercore.

Notes. The EVAP core sensor. Make sure to put it where you can get it back out, or where there is room for a replacement. If it goes out the a/c will just not turn on.

 

[IntrepidLover1956]

Evap cores are know for going bad. Honestly the dash is not the bad at taking out. Much easier if you remove the front seats and center console completely. Also best time to do heater core while in there!

Some photos of my 93 to give you an idea...

View attachment 42670

View attachment 42671

View attachment 42672

View attachment 42673

View attachment 42674

My wonderful heatercore.

View attachment 42675


Notes. The EVAP core sensor. Make sure to put it where you can get it back out, or where there is room for a replacement. If it goes out the a/c will just not turn on.

Thanks very much. I'm hoping I don't need to do that; but, if I do, I will also replace the recirculation door actuator while I'm in there.

 

[LUNAT1C]

Thanks for that info Bill. I might look into as I get closer to doing my condenser. And you've annoyingly reminded me that I forgot to order a new drier along with all my other RockAuto parts ordered recently... current one installed in 2019. Guess I'll order one along with the fuel pump seal and lock ring that my Jeep is asking for. Never ends!

Regarding heater core, that's something I would keep in the back of my mind and not necessarily plan to do. I looked up heater cores when I did my evap with the same "while I'm there" mentality, but all of them are aftermarket units now and don't appear to be the same quality as OEM. I left my original heater core in place since it appeared to still be in great shape. Other than speckles of dye, my evap looked mostly Ok as well, even the foam tray was in great shape surprisingly.

A note on my experience with the temp probe - I initially installed it in the evap before putting it into the HVAC housing, in roughly the same spot as the original. Turned out to be in a position that was barely not serviceable through the HVAC box opening, so I had to pull it back out and reinsert in a second location with the box sealed up. I would suggest doing the same to avoid making multiple holes in the fins.

 

[EagleESI]

A note on my experience with the temp probe - I initially installed it in the evap before putting it into the HVAC housing, in roughly the same spot as the original. Turned out to be in a position that was barely not serviceable through the HVAC box opening, so I had to pull it back out and reinsert in a second location with the box sealed up. I would suggest doing the same to avoid making multiple holes in the fins.

I really want to say when I did mine I read in the FSM it is suggested not to use the original placement if taken out and put back in on the same evap core.

 

[D725U]

My wonderful heatercore.

Did you replace yours with an OEM unit or some aftermarket brand?

 

[LUNAT1C]

I really want to say when I did mine I read in the FSM it is suggested not to use the original placement if taken out and put back in on the same evap core.

Right, it does. When reusing the core (and who would go to all that work and do that...), place the probe in another position.

 

[pgr1940]

I've used this product in both my cars: 00' Intrepid ES 3.5, 02' 300M. It worked.
It's important to first replace the receiver-dryer accumulator and follow the directions.

Super Seal & Additives

Cliplight A/C Leak Sealants & Additives are designed specifically to work fast and efficiently to help boost the performance of your vehicle's A/C system.

www.cliplight.com

They also make a sealer for Central Air units.

 

[peva]

I've used this product in both my cars: 00' Intrepid ES 3.5, 02' 300M. It worked.
It's important to first replace the receiver-dryer accumulator and follow the directions.

Super Seal & Additives

Cliplight A/C Leak Sealants & Additives are designed specifically to work fast and efficiently to help boost the performance of your vehicle's A/C system.

www.cliplight.com

They also make a sealer for Central Air units.

Some people claim that a.c. shops get irritated with owners who have put sealant in their system because they consider it a contaminant, so they have to purge their coolant recovery system after doing the work. Not gving you a hard time about it. Seems like if it was that big of a deal they would routinely ask each customer if they have sealant in their system, and if so, refuse to work on it. But some people might not know if it's been added, and that's when the shop gets irritated - after they've contaminate their recovery system.