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I've searched 12 of 23 pages in this forum for an answer, but haven't located one. Hopefully, this hasn't already been covered.

I replaced every part of my A/C system, except for the evaporator. The new compressor came without a manifold, so I had to use the old one.

After installing all components, I pulled a vacuum of 30, checked it after an additional 30 minutes to make certain there were no leaks in the system (vacuum held), drew vacuum for an additional 60 minutes, then recharged the system. I had good low and high side pressures, and the air from the vents was cold. The next day, I had no charge. I discovered that refrigerant was leaking from the high side service port (not certain why the system held vacuum).

I replaced the valve cores on both service ports and re-ran the vacuum/recharge process. The next day, no charge in the system. Obviously something is wrong, but I don't know where to go from here. Any suggestions?
 

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Are you putting the port caps back on? If your schraders are leaking, having the caps on would prevent loss of the charge. If still loses charge, then something besides schrader is leaking. If it keeps charge with caps on and tight, then that tells you that one or both schraders are leaking.

So - when you have been losing the charge, were your caps on and tight/sealed?
 

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Yes, I always put the caps back on, finger-tight. And I have replaced both schrader valves in the service ports. The high side was leaking after the first recharge, so I replaced both of them. I did not see any signs of leaking from the service ports after the second recharge, but obviously the refrigerant is going somewhere. Why does the system hold vacuum if there is a leak somewhere? Or are there some leaks that can't be discovered with a check of vacuum?
 

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I don't know how likely it is that a seal could leak in only one direction, such as maybe the overpressure blow-off valve? I don't know.

Did you put any UV dye in the system? If you did, then you should be in luck and be able to discover dye where the leak is. If you didn't put dye in, then that makes it a guessing game of what's leaking where.
 

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Some ideas:
• If no dye, use soap bubble mixture to spot leaks.
• Try replacing all o-rings - lubricate them with PAG oil.
• Rent a small bottle of nitrogen from the local welding supply house, such as ARC3, to pressure test the system and look for leaks (with soap bubbles). (You'll need to buy a pressure regulator/gauge for the nitrogen - on-line/Amazon is generally a lot cheaper for that than from the local welding supply house. Besides the bottle rental, you'll pay for the total nitrogen charge - costs are something like a few cents a day for the bottle, plus $15 for the total charge of nitrogen.)
• If you left the system with vacuum on it for several hours, that would be more telling of a leak - under vacuum - than for just an hour. A small leak would be a small movement of the needle over an hour. Multiply that effect by letting it sit overnight (or buy an electronic micron vacuum gauge - more $$$).
 

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Discussion Starter #6
Some ideas:
• If no dye, use soap bubble mixture to spot leaks.
• Try replacing all o-rings - lubricate them with PAG oil.
• Rent a small bottle of nitrogen from the local welding supply house, such as ARC3, to pressure test the system and look for leaks (with soap bubbles). (You'll need to buy a pressure regulator/gauge for the nitrogen - on-line/Amazon is generally a lot cheaper for that than from the local welding supply house. Besides the bottle rental, you'll pay for the total nitrogen charge - costs are something like a few cents a day for the bottle, plus $15 for the total charge of nitrogen.)
• If you left the system with vacuum on it for several hours, that would be more telling of a leak - under vacuum - than for just an hour. A small leak would be a small movement of the needle over an hour. Multiply that effect by letting it sit overnight (or buy an electronic micron vacuum gauge - more $$$).
I (stupidly) did not put any dye in the system because I had put all new parts in (except for the evaporator).

1. Is there any way to determine if the evaporator is leaking, other than a visual inspection?

2. I think I'm going to check to make sure the "o-ring" inside the manifold is OK. Then I'll pull a vacuum and let it sit overnight. I'll add dye when I recharge, if it holds vacuum.

3. I'm thinking that I haven't lost any PAG oil, just refrigerant, through the two leaks. But I've seen other threads on here where people say that I would have also lost oil with the refrigerant. Your thoughts?
 

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If there had been dye in the system, the condensate drain hose end would light up with UV light. If no dye, if the condensate hose outlet is not just wet but oily, that would be an indicator.

On PAG oil loss, I find that hard to predict. If it lost refrigerant over time thru a microscopic leak and the car or its a.c. was hardly ever used, oil loss might be minimal. However, oil loss rate would be higher even thru a microscopic leak when the a.c. was being used because of the system pressure (200-300 psi on high side vs. 70 psi throughout when not being used) and the oil is circulating with the 134A (being constantly exposed to the point of leakage) rather than settling out by gravity when the car or its a.c. is sitting unused (so oil loss would be low unless leak was at a low point in the system).

Having said all of that, since you replaced hoses, receiver-drier, compressor, etc., if the new compressor didn't come with oil already in it, you definitely need to add oil, as a certain quantity is distributed more or less evenly throughout the system, so a definite amount pools in each hose and component, especially the compressor sump, when the car sits unused.

The only way to know for sure after it's been running is to flush the system to get everything out. That should be done anyway after a compressor fails because metal particles will have been distributed throughout. A new compressor warranty will be voided if it wasn't flushed out.

Below is a table from the FSM to be used as a guide on how much oil should be added back for replacement of each component. The compressor should have come with some in it, but you're supposed to drain and measure to be sure when installing it. If so, you're probably OK. If it came with a full 5 ozs., you have that plus whatever remained in the evaporator. Ideally, you would have poured out what was in the new compressor and put back in whatever would be needed to give 5 ozs. total. there's an allowable tolerance on that. Think of the uncertainty as having a half qt. of oil over or under in the engine crankcase.

41003
 

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Discussion Starter #8
I didn't have a compressor failure - I just decided to install new parts because of the age of the system (and because I had a leak in the condenser). The only part that, perhaps, wasn't clean was the evaporator because I did not replace it.

I looked over the system today with good lighting. I could see vapor coming from the rear of the compressor. I think I'm going to remove the hoses, remove the compressor, try to locate the leak, replace the "0-ring" between the manifold and the compressor, drain the compressor oil, put new oil in, see if it will hold vacuum for 8-10 hours, and recharge. If that doesn't fix it, I'll have to do without A/C until sometime next year as I can't afford to pay someone to sort it out.

I appreciate your quick replies.
 

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I didn't have a compressor failure - I just decided to install new parts because of the age of the system (and because I had a leak in the condenser). The only part that, perhaps, wasn't clean was the evaporator because I did not replace it.

I looked over the system today with good lighting. I could see vapor coming from the rear of the compressor. I think I'm going to remove the hoses, remove the compressor, try to locate the leak, replace the "0-ring" between the manifold and the compressor, drain the compressor oil, put new oil in, see if it will hold vacuum for 8-10 hours, and recharge. If that doesn't fix it, I'll have to do without A/C until sometime next year as I can't afford to pay someone to sort it out.

I appreciate your quick replies.
Glad to hear you didn't have a compressor failure. That relieves a bit of concern for serious system contamination.

Your plan sounds good.

On seeing vapor coming from the rear of the compressor - that is hopeful that you found your leak area.

NOW consider this: The over-pressure relief valve (which I mentioned in my previous post) is in that area - part of the head/manifold - see sketches from FSM, below. Convince yourself that the relief valve is or is not the problem. If it is, that could explain holding vacuum, but not holding positive pressure. Not saying that that definitely is your problem, but prove it one way or the other to ensure yourself the shortest path to success.

You mentioned having to re-use the manifold. I noted in some of my old posts that I thought it was misleading for the compressor manufacturers' product photos to show the manifold on their compressors, then when you receive your new compressor, you discover that you have to re-use your old manifold. Basically false advertising. And what if you had already thrown your old compressor (with manifold) away - or what if your pressure relief valve is defective!

Anyway - I hope you're able to quickly get to the end of this long ordeal.

41005


41007
 

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Once again, thanks for your suggestions. I have a vacuum pump being shipped (I had been using a "free loaner" from Autozone, but decided that involved way too much hassle and inconvenience). I will post results of the additional work after completion.
 

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It is possible to leak under pressure but not under vacuum depending on a seal or something. Did you inspect the mating surfaces for manufacturing defects? I have seen some head scratching mistakes from factory, rare but it happens. Nylog blue is better to coat seals with, also it's not hygroscopic like PAG and good to put on valve cores. If you had a universal bag of seals make sure you used the correct size, there are many sizes and some are very close but not right.
 

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I've searched 12 of 23 pages in this forum for an answer, but haven't located one. Hopefully, this hasn't already been covered.

I replaced every part of my A/C system, except for the evaporator. The new compressor came without a manifold, so I had to use the old one.

After installing all components, I pulled a vacuum of 30, checked it after an additional 30 minutes to make certain there were no leaks in the system (vacuum held), drew vacuum for an additional 60 minutes, then recharged the system. I had good low and high side pressures, and the air from the vents was cold. The next day, I had no charge. I discovered that refrigerant was leaking from the high side service port (not certain why the system held vacuum).

I replaced the valve cores on both service ports and re-ran the vacuum/recharge process. The next day, no charge in the system. Obviously something is wrong, but I don't know where to go from here. Any suggestions?

After pulling a vacuum I let them sit for 24 hours.
 

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Discussion Starter #15
After pulling a vacuum I let them sit for 24 hours.
I don't have that option. However, I plan to let it sit for 10 hours the next time I pull a vacuum. I don't think that will necessarily help - I have a leak only when the system is pressurized. I think it may be the relief valve on the rear of the compressor.
 

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Discussion Starter #16
You may need to use dye to find the coolant leak. Can be a real time saver.
I'm planning to put that in the next time I charge the system. I didn't do it the first time because I installed all new components. However, I now see an oily residue on the back end of the compressor, so I'm going to check into that further.
 
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