A/C Leak(?)

LEMBERGS

MEMBER
1996 DODGE INTREPID
3.5L
V6
2WD
AUTOMATIC
306,435 MILES

I replaced all components of my A/C system last summer (except for the evaporator). I put the PAG oil in according to the manufacturer's instructions. I vacuumed the system, and it held the vacuum. I then charged it with the required amount of refrigerant. It worked GREAT, but only for about 24 hours. When I put the manifold gauges on it, the system had no pressure. I'm stumped.

1.) Why would the system have no leak under vacuum but lose all refrigerant when under pressure?
2.) Provided I can find the source of the leak, will I need to add PAG oil? (I know that vacuuming the system down doesn't remove the PAG oil, but would I have lost any due to the leak (wherever it is))?
3.) In the event that I need to add PAG oil, is there a simple way to determine how much, or do I need to drain the oil from the compressor and then fill it with the specified amount. I know that too much oil reduces the effectiveness of the refrigerant and will decrease the cooling capacity.
4.) Is there anything else I should be aware of?

Thanks,
Chuck

7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Let's start at the beginning because I think you are basing this on some assumptions. At least that is what it seems with the info that you provided.

So, let's start with what the actual pressure is when the A/C is on and off.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Once we know what the pressure is we can take the next step.

However, if the pressure is 0 then the system is empty as you stated. So that means we may not have had an issue when you pulled it into a vacuum but then the leak developed later. So, we need to redo the vacuum test to try and find the leak.

Here is a guide that will help with this:

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

However, the leak may not be bad enough to leak right away so we need to pull it into a vacuum and the system should hold that vacuum for at least an hour.

Here is a guide that will help with finding the leak but if you added dye the last time you charged the system then we can jump right to that step in looking for the dye:

https://youtu.be/yrhWKlQEPWw

Lastly, if you have a leak then you most likely do not need to add oil back into the system. The only oil you will need to add is that amount of oil that comes out when you vacuum the system.

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Saturday, June 25th, 2022 AT 9:18 AM

LEMBERGS

MEMBER
4 POSTS

I vacuumed down my system earlier today and charged it with 28 oz. Of refrigerant as per the specs. My vent temperature went from 93.3 to 57.2 F. Static pressure ended up at 115 psi, which reflected a temperature of 92 F on the manifold gauges. After the recharge, my pressures were 34 on the low side and 255 on the high side. I used a refrigerant "sniffer", which I recently purchased, to check for leaks. I found none within the engine bay. If the system loses pressure again, what would you suggest?

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Saturday, June 25th, 2022 AT 4:16 PM

KASEKENNY

MECHANIC
18,907 POSTS

If you find no leaks in the engine bay, you need to access the evaporator by removing the blower motor and use your sniffer in there.

That is great that you have one of those. It will make this much easier.

However, don't neglect checking the engine bay again. Clearly a leak is a leak so if it is not leaking right now then you would think it is not going to leak but there are exceptions to every rule so just cover the engine bay each time you check it just to be sure.

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Saturday, June 25th, 2022 AT 4:26 PM

LEMBERGS

MEMBER
4 POSTS

Okay. The system vacuumed down and charged to capacity four days ago. I borrowed another vehicle until today, which was the first time I could check my A/C. Not even enough in the system to trigger the compressor clutch. I guess I'll need to recharge and look for leaks at the evaporator, which I have not yet done. I really expect it to be the evaporator at this point, though.

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Wednesday, June 29th, 2022 AT 5:42 PM

KASEKENNY

MECHANIC
18,907 POSTS

I don't disagree. If you found no leaks prior, then that would make sense.

However, you may not need to charge it again if dye was in the system.

You can also just access it and look for oil residue because some of that would have come out. However, Freon with that leak detector would be easier.