Air condition leak?
 

Hi,
I have a 2008 3.0sd, and i have a strange problem with the aircondition.
It seems that i have a leak somewhere, but nobody can't find where is it.
I have checked the car to 2 different dealerships, and maybe more than 5 other shops.
Everybody says that there is no leak, as it passes the vacuum test, And they cant find any of the dye that they put inside.
The strange thing is that, as along as i use the car daily, there is no problem.
When I don't use it for a day or two, then i it is almost out of refrigerant.
Does anybody have a clue about this?

Thanks

When you do not use the AC for two days the old seals on the compressor are not wetted and their leak rate increases.

I went looking and was unable to determine whether BMW uses a scroll type compressor or a piston compressor. My experience suggests that a scroll compressor retains its charge better. Perfectly in my VW which AC worked perfectly for 13 years untouched.

Thanks a lot for the info.
Do you know if this can be repaired or I have to change the compressor?

Unexpert, I think must be replaced. I believe that AC compressors are commoditized and not expected to be repaired.

The dye is in the lubricating oil that is way too viscous to be lost through the seals; mere fiber labyrinth seals as I recall, maybe with a couple of rubber slinger/scrapers.

The refrigerant comes into the compressor as a warm medium pressure vapor and leaves as a high pressure hot low viscosity liquid. Phase change happens twice in a heat pump loop, at the expansion valve and in the compressor.

In my work we used various electronic sniffers and chemical torch freon leak detectors and monitored the general atmosphere for refrigerants among other things.

There's been several reports of the X5 leaking at the evaporator which requires basically disassembling the whole interior.

Have you noticed any funny smell coming the vents? Like something that smells "sweet"?

PS: found out that replacing the evaporator takes about 2 minutes: https://youtu.be/W5Oe6cajjjg

The smell has also been likened to that of a fresh band-aid or 'elastic bandage'

With the evap in the dash, then cannot readily see the dye, but a sniffer for Freon can find it