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996.1 Carrera 2 - Engine whine identified !?

First off i'm no expert .. i just say what i see .. and i'm not always right.

oil doesn't boil in a vacuum .. water / moisture does so the vacuum side is to remove water basically .

if you remove a compressor and drain it out you will get in the region of 40 grams of oil out .. there are 195 in the entire system .. think about it .. spray a lub ( aerosol can ) over a length of pipe .. a small amount covers a large area and so it is with the a/c .. the inside of the pipes .. condensers , evaporators etc etc all have oil in them , coated is a better word.

Evaporator and the pipes are at the top so a reasonably amount of oil can sit in it .. there is no way to actually get it out other than removing it and upending it to drain out .

It doesn't really matter other than how do we know there is the correct amount of oil in the system ..

If someone has an answer here then please let me know as i don't .

I base it on what comes out on an a/c regas .. if no oil comes out ill add some .. if i get 5-6 grams then i consider its fine .

A vacuum hold test .. you need about 30 mins here will tell you if there's a leak ... machines are pretty much auto these days so it just does it . but we can specify the duration of the test .

There is a chart on this post about the amount of oil in different components .

http://911uk.com/viewtopic.php?p=1463074#1463074

bear in mind .. too much oil can hydrolock the compressor .. never seen to little so far though but it would seize the compressor in theory .
 
I am no expert, but have had this issue on my 996.2 in the past.

Once it was insufficient gas.

The condensers were replaced when I bought it and there was a subsequent leak from a pipe joint. My AC guy told me its therefore impossible to know how much oil is in the system as the machine cannot recover all of it.

When I next had the AC serviced, it whined a lot. The AC guy re-pulled the gas and added 10ml of oil. Noise went away for a while.

It would always return over time and next AC had another 10ml added. Again quiet for a time and then returned.

Air con always worked fine.

Unless you want to get balls deep in a full strip, repair/replace of condensors, compressor, receiver dryer etc, my advice service it regularly and turn the stereo up.
 

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