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Old 09-26-2012, 02:48 PM   #1
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A/C problems still a mystery

Hi Guys,

for the past 2 months I have been having problems with my Boxster's A/C. When filled with refrigerant, after 2-3 weeks, gas leaks and A/C stops cooling. My mechanic filled it with nitrogen, both low and high pressure lines, at 21 bar, and after almost a month, the pressure is still stable at 21 bar. Obviously I can not test the A/C unit as it is filled with nitrogen at a very high pressure - it would be a disaster. Any ideas how the refrigerant is being lost?
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Old 09-26-2012, 03:46 PM   #2
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Try this.
-Fill the A/C system with refrigerant.
-DON'T USE the A/C for 3 weeks.
-After 3 weeks, check the pressure.

Good luck.
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Old 09-26-2012, 06:18 PM   #3
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When you recharge the system, use a can of 134a that includes oil and a dye. After a coupler of weeks, use a black-light flashlight to see if you can find the dye anywhere near the A/C system. If so, you have a leak. If not, check for the dye in the pool of condensation that shows up under the car. This means the evaporator may be leaking.
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Old 09-27-2012, 12:04 AM   #4
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I recall that the last time we used a dye, It was visible on the back right side cover near the wheel well (close to the CAT). Is that where the pool of condensation exits? If so does it make sense that it only leaks when used?
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Old 09-27-2012, 03:49 AM   #5
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Quote:
Originally Posted by rene525d View Post
I recall that the last time we used a dye, It was visible on the back right side cover near the wheel well (close to the CAT). Is that where the pool of condensation exits? If so does it make sense that it only leaks when used?
Yes, bad compressor seals will do this...........I would reexamine where the dye was seen.
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Old 09-27-2012, 11:23 AM   #6
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Would a stop leak be ideal in this case, or is it always better to change and worn seals if possible? Am i undderstanding correctly that if the dye is only visible on the back right near the wheel well, it is most likely a compressor seal issue? I want to rule out the evaporator, as this is such a headache to replace.
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Old 09-27-2012, 11:42 AM   #7
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I am not a fan of additives to attempt to stop leaks, they often cause more issues than they cure.
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Old 09-27-2012, 03:28 PM   #8
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Quote:
Originally Posted by rene525d View Post
I recall that the last time we used a dye, It was visible on the back right side cover near the wheel well (close to the CAT). Is that where the pool of condensation exits? If so does it make sense that it only leaks when used?
the compressor is located on the left side of the engine, so i don't think it is leaking from the compressor it self.
how ever, the AC lines from the compressor to the evaporator, are running along the right side of the car (10 and 6 in the fig). i read in another tread, that sometime this lines are pinched when the car is not lifted correctly.
also consider (more likely) that the leak is coming from O-Rings 18&19. they are located right next to the right rear wheel.
if the evaporator was leaking, you will have a funky small in your air vents.
you will also be able to see the dye coming out with the condensed water coming out exactly in the center of the car.

edit: forgot to add the fig.
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Old 09-27-2012, 03:30 PM   #9
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AC system

here you go.
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Old 09-27-2012, 03:56 PM   #10
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Only problem with that logic is that any buggered line, dryer, fitting, oring, sensor, evap unit, etc. would continue to leak when the system is filled with N2, which is appears not to be doing; the only thing that would not leak would be the compressor because it is not running. Often the compressor seals leak only when a low area on the shaft passes the damaged seal arear while the unit is turning, but with nitrogen in the system preventing the unit from running, the shaft is not moving. Boosting the pressure beyond the normal running pressures would also tend to "push" the compressor seals more than normal, also slowing or stopping the leaks.
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Old 09-27-2012, 06:00 PM   #11
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Originally Posted by JFP in PA View Post
Only problem with that logic is that any buggered line, dryer, fitting, oring, sensor, evap unit, etc. would continue to leak when the system is filled with N2, which is appears not to be doing; the only thing that would not leak would be the compressor because it is not running. Often the compressor seals leak only when a low area on the shaft passes the damaged seal arear while the unit is turning, but with nitrogen in the system preventing the unit from running, the shaft is not moving. Boosting the pressure beyond the normal running pressures would also tend to "push" the compressor seals more than normal, also slowing or stopping the leaks.
Exelant point. Just another lesson I learned from you JFP
Hope for you Rene, that fixing the compressor will solve the problem for you.
Much easier then replacing the evaporator.
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Old 09-27-2012, 08:01 PM   #12
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Originally Posted by JFP in PA View Post
Yes, bad compressor seals will do this...........I would reexamine where the dye was seen.
Hi JFP.

Are the compressor seals replaceable items? Or, do you have to replace the entire compressor?

Thank you.
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Old 09-27-2012, 10:59 PM   #13
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Thanks JFP. It was filled with N2 at 21 bar, and as of yesterday evening, it was still at 21 bar. As stated previously, are the compressor seals replaceable?
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Old 09-28-2012, 06:10 AM   #14
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Yes, but it takes a lot of specialized fixtures and tooling to do it properly and bench test the unit, cheaper to just replace it and trade in your old core. It is also very difficult to get parts for the unit.

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