Automotive Air Conditioning Information Forum

Posted: **Wed Aug 06, 2025 6:35 am**

: ac.jpg (112.24 KiB) Viewed 614 times

2011 Camaro SS, about 97000 Miles.

AC works fine when charges, compressor has a bit of a whine.

After sitting for a few days, all the freon leaks out. Here is what I have done:
- Put dye in system - cannot see any significant signs of leakage, aside from maybe low pressure port.
- Replace high pressure port with Schrader valve.
- Replaced Schrader valve in low pressure port.
- System has been on vacuum for 48 hours - still holding.

My conclusions - correct me if I am wrong.
- If the system is holding a vacuum - tells me that the static systems are good ( condenser, evap core) the leak is at a flexible seal point (oring, schrader port)
- AC compressor was replaced at 45,000 miles.
- When I removed cap from low pressure port I heard gas escape. This was after replacing the core.

Next steps:
- Charge system, use soapy bubble test on junctions & ports under pressure.
- Replace plastic port covers with new metal ones

Posted: **Wed Aug 06, 2025 6:36 am**

Low pressure port cap

: ac2.jpg (215.55 KiB) Viewed 613 times

Posted: **Wed Aug 06, 2025 3:40 pm**

Ex313 wrote: Wed Aug 06, 2025 6:35 am AC works fine when charges, compressor has a bit of a whine.

If the new compressor came "dry," did you add any oil?

Ex313 wrote: Wed Aug 06, 2025 6:35 am After sitting for a few days, all the freon leaks out. Here is what I have done:
- Put dye in system - cannot see any significant signs of leakage, aside from maybe low pressure port.
- Replace high pressure port with Schrader valve.
- Replaced Schrader valve in low pressure port.
- System has been on vacuum for 48 hours - still holding.

If you injected UV dye into the system (no more than 1 ounce), did you subsequently check for leaks in a darkened garage or at night using the special flashlight and glasses? Did you check for the presence of dye in the evaporator condensate?

A leak or leaks could be anywhere. Some common leakage points are at the bottom of the condenser, anywhere on the condenser due to physical damage (stones kicking up, front-end collision, etc.), lines routed down low developing pinholes due to caustic chemicals used to melt ice in winter, at the evaporator (vegetable matter mixing with moisture and causing corrosion), at the compressor shaft seal or seams, and anywhere there's a joint and/or o-ring.

Schrader valves normally leak a little bit. It's the cap the provides the actual seal.

A vacuum that's holding doesn't necessarily mean that the system won't leak under pressure.

In your first photo, I see only about 26 inHg on the LS gauge. Was this reading after you let it set for 48 hours, or during evacuation? If it was during evacuation, that gauge reading suggests contaminated vacuum pump oil, a defective vacuum pump, or you live at a high elevation, in which case 26 inHg would probably be normal. Is the gauge itself zeroed?

Ex313 wrote: Wed Aug 06, 2025 6:35 am My conclusions - correct me if I am wrong.
- If the system is holding a vacuum - tells me that the static systems are good ( condenser, evap core) the leak is at a flexible seal point (oring, schrader port)
- AC compressor was replaced at 45,000 miles.
- When I removed cap from low pressure port I heard gas escape. This was after replacing the core.

See above.

Ex313 wrote: Wed Aug 06, 2025 6:35 am Next steps:
- Charge system, use soapy bubble test on junctions & ports under pressure.
- Replace plastic port covers with new metal ones

You'll need only a few ounces of refrigerant for leak checking using an electronic leak detector, also known in the trade as a "sniffer." Otherwise, you might need a full or nearly full charge of refrigerant to force out the dye.

You might not be able to find metal service-port caps to fit. Plastic caps are fine as long as the sealing rings are in place inside each cap. The cap pictured doesn't look like it has a sealing ring.

The specifications that I have for your car call for 21 ounces net weight of R-134a, and 4.1 fluid ounces of PAG-46.

Posted: **Wed Aug 06, 2025 8:19 pm**

JohnHere wrote: Wed Aug 06, 2025 3:40 pm
Ex313 wrote: Wed Aug 06, 2025 6:35 am AC works fine when charges, compressor has a bit of a whine.
If the new compressor came "dry," did you add any oil?

I just bought the car in February, dealership replaced it at 47,000 miles. Car has 98,000 on it now. I assume they followed proper protocol on replacement.

Ex313 wrote: Wed Aug 06, 2025 6:35 am After sitting for a few days, all the freon leaks out. Here is what I have done:
- Put dye in system - cannot see any significant signs of leakage, aside from maybe low pressure port.
- Replace high pressure port with Schrader valve.
- Replaced Schrader valve in low pressure port.
- System has been on vacuum for 48 hours - still holding.
If you injected UV dye into the system (no more than 1 ounce), did you subsequently check for leaks in a darkened garage or at night using the special flashlight and glasses? Did you check for the presence of dye in the evaporator condensate?

Yes. I did not see any evidence.

A leak or leaks could be anywhere. Some common leakage points are at the bottom of the condenser, anywhere on the condenser due to physical damage (stones kicking up, front-end collision, etc.), lines routed down low developing pinholes due to caustic chemicals used to melt ice in winter, at the evaporator (vegetable matter mixing with moisture and causing corrosion), at the compressor shaft seal or seams, and anywhere there's a joint and/or o-ring.

Schrader valves normally leak a little bit. It's the cap the provides the actual seal.

A vacuum that's holding doesn't necessarily mean that the system won't leak under pressure.

In your first photo, I see only about 26 inHg on the LS gauge. Was this reading after you let it set for 48 hours, or during evacuation? If it was during evacuation, that gauge reading suggests contaminated vacuum pump oil, a defective vacuum pump, or you live at a high elevation, in which case 26 inHg would probably be normal. Is the gauge itself zeroed?

Its a home gauge ( my son is in hvac and his vac pump didn't have a fitting for my auto gauges.) That reading is after 48 hours, it was at 30 during vacuum.

Ex313 wrote: Wed Aug 06, 2025 6:35 am My conclusions - correct me if I am wrong.
- If the system is holding a vacuum - tells me that the static systems are good ( condenser, evap core) the leak is at a flexible seal point (oring, schrader port)
- AC compressor was replaced at 45,000 miles.
- When I removed cap from low pressure port I heard gas escape. This was after replacing the core.
See above.

Ex313 wrote: Wed Aug 06, 2025 6:35 am Next steps:
- Charge system, use soapy bubble test on junctions & ports under pressure.
- Replace plastic port covers with new metal ones
You'll need only a few ounces of refrigerant for leak checking using an electronic leak detector, also known in the trade as a "sniffer." Otherwise, you might need a full or nearly full charge of refrigerant to force out the dye.

I looked over the car with a UV light, looks to be previous dye splatter on the engine. Did not see a strong single source come out. I am thinking that I will recharge it, run it and have a friend with a sniffer see if anything some up for him. After that I think the next step if I can't find anything is to do a nitrogen pressure test and see what it reveals.

You might not be able to find metal service-port caps to fit. Plastic caps are fine as long as the sealing rings are in place inside each cap. The cap pictured doesn't look like it has a sealing ring.

I planned to replace those.

The specifications that I have for your car call for 21 ounces net weight of R-134a, and 4.1 fluid ounces of PAG-46.

Posted: **Thu Aug 07, 2025 8:20 am**

Ex313 wrote: Wed Aug 06, 2025 8:19 pm I just bought the car in February, dealership replaced it at 47,000 miles. Car has 98,000 on it now. I assume they followed proper protocol on replacement.

Do you happen to know whether the A/C system was leak free and working until just recently?

Ex313 wrote: Wed Aug 06, 2025 8:19 pm Yes. I did not see any evidence (of leakage).

However, it must be a pretty big leak if the refrigerant bleeds out in just a few days.

Here's another procedure to try: Wrap a shower cap or snug fitting plastic bag around the clutch area of the compressor, securing it to the compressor case with a sturdy rubber band. After a couple of hours, slip the probe of a sniffer underneath the cap or bag to see whether the sniffer alarms. If it does, then the compressor shaft seal is leaking. The repair is to replace the compressor and the condenser assembly. The Receiver/Dryer is integral with the condenser, so you won't have to replace that separately.

Ex313 wrote: Wed Aug 06, 2025 8:19 pm Its a home gauge ( my son is in hvac and his vac pump didn't have a fitting for my auto gauges.) That reading is after 48 hours, it was at 30 during vacuum.

Okay, that explains the gauge being calibrated for R-12, R-22, and R-502 but not for R-134a.

If the gauge read ~30 inHg during evacuation, that's good. But it must have lost vacuum during the 48 hours you let it set because the gauge now appears to read ~26 inHg. The discrepancy might be due to outgassing, a leak, or an uncalibrated (zeroed) gauge.

Ex313 wrote: Wed Aug 06, 2025 8:19 pm I looked over the car with a UV light, looks to be previous dye splatter on the engine. Did not see a strong single source come out. I am thinking that I will recharge it, run it and have a friend with a sniffer see if anything some up for him. After that I think the next step if I can't find anything is to do a nitrogen pressure test and see what it reveals.

Sounds like a good plan. Be sure to re-charge it by weight, not pressures, in accordance with Best Practices. Remember that a sniffer can't detect pure nitrogen, so you'll have to use the visual approach: UV dye or soap bubbles.

Ex313 wrote: Wed Aug 06, 2025 8:19 pm I planned to replace those.

Good deal.

Posted: **Fri Aug 15, 2025 10:23 am**

I pressurized the system to about 80 psi and tested all visible joints and ports with soapy water - no leaks visible. The system still had a 20 inHg vacuum from two weeks ago. Am I wrong in my thinking that its probably a soft seal like a compressor and not something solid like a condenser. The rationale being if a pipe had a hole in it - it would bleed down to nothing eventually. The fact the system holds a vacuum for a couple weeks makes me hopeful its not something like an evap core.

The compressor does sound like a supercharger when engaged - so that may be the problem again.

Next step is to charge and run over the system with a sniffer to see if I can confirm the location of the leak.

Posted: **Sat Aug 16, 2025 2:29 pm**

Although the system seems to leak-down very slowly while under vacuum, it might not leak under pressure (an opposite force).

Suggest changing the R/D desiccant element, evacuating, and recharging it. Then leak-check it with a sniffer, as you suggested. If no leaks turn up, and it cools sufficiently, then just use the A/C system as you normally would.

Posted: **Sun Aug 17, 2025 11:05 am**

How can you test the vacuum while the system is under pressure? (post 6)
The discrepancy might be due to outgassing, a leak, or an uncalibrated (zeroed) gauge. OR a vacuum driven so-called vacuum "pump" such as you can buy at Horrible Fright was used. These devices are a joke because they CANNOT attain sufficient vacuum.
Using a sniffer on the system is the best approach, else you are wasting time. Be sure the sniffer probe is inserted into the drain port or tube from the evap; this is how you test the evap for leaks.
Just because a dealer did some work doesn't mean it was done correctly, sorry to say. Not all repair men truly understand the nuances of auto AC

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