Cayenne 958 air conditioning puzzle

  • Dear Porsche community,

    Until recently, the air conditioning system in my 2012 Cayenne was empty because a line was no longer inserted correctly during a repair in the workshop and the rubber was rusting. A loud hissing noise was audible when the pressure was applied, so that the open line was found immediately. This was repaired, new rubber was fitted and the air conditioning seemed to be tight ever since.

    Then, after a simple pressure test (squeezing), the system was refilled with leak detector (UV) for about 10 minutes, but it only stayed in for about 10 days, then the system was again without function and the test showed: also completely empty again. So back to the workshop, but none of the three tests carried out (UV light, pressure test, complete visual inspection without removal) produced any results.

    So where has the agent gone if you can't see anything in the engine compartment on the driver's side and from the front on the air conditioning condenser? An acquaintance said that there is often an unnoticed hole in the lines to the rear center console - but I only have one evaporator, so I'm sure there are no lines in that place. Have any of you ever had anything like this? What else could be the cause?

    Would be very grateful for any solutions - especially as temperatures rise...

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  • Thanks for the tips on the air conditioning system.

    For anyone with similar problems, here is how to proceed:

    1. Porsche said that with two evaporators, the rear lines towards the rear are often overlooked in the event of a leak. However, according to Porsche, mine only has one evaporator, so everything must be happening at the front, in the engine compartment.

    2. if a leak detection additive is filled in, you should be able to determine somewhere where it is leaking. If the lines that can be seen from the engine compartment and underbody are clear, you can use an endoscope camera to check the evaporator, which is located in the heater box, for leaks; to do this, you have to remove various panels in the footwell and possibly also the blower motor.

    3 However, working with the evaporator only makes sense if leak detection agent has entered the vehicle interior. The lines to the inside were therefore checked as follows: a UV lamp was used to look into the ventilation slots in the interior to see if anything was visible. This was not the case, so the evaporator suspicion was abandoned.

    4. as nothing was visible in the engine compartment on the air conditioning radiator - i.e. no stone chips etc. from the front, for example. - Since nothing was visible in the engine compartment on the air conditioning radiator - i.e. no stone chips etc. from the front, but a little on the radiator access lines, all 5 sealing rings (of different sizes) were now replaced - that should have been all of them for an evaporator in the engine compartment (except for two more directly in the interior, which are not easy to get to).

    5. the two rubber seals towards the interior were checked with a camera, but nothing was visible (which is not to say that there is nothing there - you can't get at it with UV light anyway - but if there was a real leak, so much leak detection agent would have to be pressed out towards the engine compartment that you would have to see it without a camera but with a UV lamp).

    6) The next step is to pressurize the system again with gas for about an hour to see if it is still leaking. However, this test is not 100% reliable even overnight, as the workshop told me. Then I'll refill the system again if nothing major is visible, and then I hope that the system will be tight after changing all the rubbers in the front engine area.

    By the way, I bought this leak detection lamp for 25 Teuros with safety goggles and am impressed by its performance:

    Alonefire SV128 395nm UV flashlight 128 LED black light flashlight

    https://amzn.to/4cnCg1Y [Advertisement]

    Older leak detector from 2023 shows it as green-yellow-pale, new leak detector from 2024 shows it as bright yellow-bright...


    Here are the 5 rubbers that I replaced (I don't have the line to the rear shown in the picture):

    The two rubber seals at the top of the red box towards the interior can only be accessed with considerable effort.

    As no leak detector was visible there, they were left as they were...

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  • Wow, what a troubleshooting !!!

    That was done by a PZ ?

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  • Hi Tom!

    No, only point 1 came from the PZ...

    Everything else I did or arranged with a friend who is a master mechanic.

    Unfortunately, he can't fill the air conditioning, so I had it done by the Bosch service at home.

    Unfortunately, the nearest service center is also quite far away from me.

    But I was there for all the work and was allowed to help...

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