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iceboy
Spa-Francorchamps


Joined: 18 Apr 2013
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Location: Berkshire


PostPosted: Wed May 25, 2016 7:38 am    Post subject: 996.1 Carrera 2 - Engine whine identified !? Reply with quote

Hi All,

After a lot of jiggery pokery.......I finally (as previously suggested) figured out the my Air Con is making the intermittent whining sound.

When the whining occurs, if I switch off the AC * on the dash, the whine stops immediately.

So the question is, what is making this noise, is it dangerous to the engine/car and what needs to be done??

Thanks in advance.
IceBoy
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Gareth64
Silverstone


Joined: 20 Mar 2016
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Location: United Kingdom


PostPosted: Wed May 25, 2016 8:01 am    Post subject: Reply with quote

As you've said engine whine I presume you mean from the back end?

I think it's a low A/C gas level, probably due to a small leak in one of your condensers.

I hear exactly the same thing in my 996TT and whilst it still blows cold, when the car was in for a minor service the guy said there's a small leak in one of the condensers.
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Avon
Trainee


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PostPosted: Wed May 25, 2016 8:17 am    Post subject: Reply with quote

Agree with Gareth. My car (also 996.1 C2) was doing exactly the same thing. A/c would blow cold(ish) but the compressor sounded like it was labouring. Went and got the system tested and regassed, now works fine.

A/c systems do leak over time even when everything is fine. Mine passed all the pressure tests, just needed a gas topup. Approx cost of a test and regas should be about 50-60 pounds
 
  
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iceboy
Spa-Francorchamps


Joined: 18 Apr 2013
Posts: 368
Location: Berkshire


PostPosted: Wed May 25, 2016 8:23 am    Post subject: Reply with quote

Thanks guys!

The AC is nice and cold but I will get it re-gassed.

Am I right in thinking the re-gassing has some form or lubrication in it?

IceBoy
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Gareth64
Silverstone


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PostPosted: Wed May 25, 2016 8:29 am    Post subject: Reply with quote

Yeah I think there's 2 parts to what goes into the system, the refrigerant itself and lubricating oil as well. I think that's correct?
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Avon
Trainee


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PostPosted: Wed May 25, 2016 10:14 am    Post subject: Reply with quote

About 25mls of lubricant.

A proper a/c service will take about an hour and involve removing all the a/c fluids, pressure testing, nitrogen flush and the separate replenishment of both the refrigerant and lubricant. Also a good technician will spend a fair bit of time with a UV torch looking for leak / spill evidence around condensers and filling points. A simple topup of refrigerant is not enough and could damage the system, because the refrigerant / lubricant mix needs to be correct. See if you can watch the procedure and ask questions, it's worth knowing about it.
 
  
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6680
Location: Brighton


PostPosted: Wed May 25, 2016 6:59 pm    Post subject: Reply with quote

Avon wrote:
About 25mls of lubricant.

A proper a/c service will take about an hour and involve removing all the a/c fluids, pressure testing, nitrogen flush and the separate replenishment of both the refrigerant and lubricant. Also a good technician will spend a fair bit of time with a UV torch looking for leak / spill evidence around condensers and filling points. A simple topup of refrigerant is not enough and could damage the system, because the refrigerant / lubricant mix needs to be correct. See if you can watch the procedure and ask questions, it's worth knowing about it.


Quick question .. how do you get the Pag oil out ?


Only asking as theres about 200ml in the system.

http://www.5150motorsport.com/porsche-a-c-refrigerant-capacity/
 
  
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Chris_in_the_UK
Estoril


Joined: 19 Mar 2014
Posts: 3577
Location: Harrogate


PostPosted: Wed May 25, 2016 7:05 pm    Post subject: Reply with quote

Demort wrote:


Quick question .. how do you get the Pag oil out ?


My understanding is that when the system looses gas and therefore has poor circulation by virtue of it having next to nothing to compress/boil the remnants of the oil settle out and usually show themselves with staining of the aircon rads?
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deMort
Long Beach


Joined: 21 Mar 2015
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PostPosted: Wed May 25, 2016 7:09 pm    Post subject: Reply with quote

I was interested to know how you get all the pag oil out with an A/C service thats all .. new one on me and always interested in tips Wink
 
  
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Chris_in_the_UK
Estoril


Joined: 19 Mar 2014
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PostPosted: Wed May 25, 2016 7:19 pm    Post subject: Reply with quote

Demort wrote:
I was interested to know how you get all the pag oil out with an A/C service thats all .. new one on me and always interested in tips Wink


Sorry mate - misread your earlier post.

If it's a straight regas then some of the oil is withdrawn with the refrigerant during the vacuum - it is important to measure what is extracted to ensure that it is not subsequently over oiled on regas.

Some numbers here:-

http://www.denso-am.eu/media/27145/denso-practical-tip-compressor-oil.pdf
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Pickse
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Joined: 20 Jul 2013
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PostPosted: Wed May 25, 2016 7:57 pm    Post subject: Reply with quote

Demort wrote:
I was interested to know how you get all the pag oil out with an A/C service thats all .. new one on me and always interested in tips Wink


My understanding is that if/when the system is vac'ed down to c. -1000mb, then fluids in the system (i.e. the gas and oil) will boil (at those low pressures) and be extracted by the vac pump.

It is commercial heat pumps in my equipment but I'm sure the same physics apply
We only use Nitrogen to leak test, removal of gas & lube is done by vac.

Changing to a different refrigerant in the same system is more complex as the lubricants can be incompatible.
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Harvster
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Joined: 08 Jan 2019
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Location: Derbyshire


PostPosted: Mon Apr 15, 2019 2:30 pm    Post subject: Reply with quote

I seem to have the same issue as the OP mentions and have come across this post through the search.

I plan to get the A/C system checked and regassed but wondered, can this be done anywhere (i.e an air-con specialist) or do you think the car should still go to a Porsche specialist?
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Robertb
Dijon


Joined: 01 Sep 2003
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2002 Porsche 996 Carrera 4S

PostPosted: Mon Apr 15, 2019 2:54 pm    Post subject: Reply with quote

I got a mobile air con specialist to do mine.

By all accounts the systems at Quik Fit are plug and play, likely the same unit a Porsche Indy would have anyway.
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maldren
Suzuka


Joined: 07 Oct 2016
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PostPosted: Mon Apr 15, 2019 4:41 pm    Post subject: Reply with quote

KwikFit will be fine for re-gassing, the question arises if there is an issue.

My car had a leak from a joint at the OSR, quite common as people jack them up carelessly under the pipe. 9E traced the problem and fixed it for me.

The other common areas for problems is the condensors, I changed mine, quite easy really but I wouldn't let Kwikfit near it.
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asterix_the_gaul
Barcelona


Joined: 20 Dec 2008
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1999 Porsche 996 Carrera 2

PostPosted: Mon Apr 15, 2019 6:52 pm    Post subject: Reply with quote

Harvster wrote:
I seem to have the same issue as the OP mentions and have come across this post through the search.

I plan to get the A/C system checked and regassed but wondered, can this be done anywhere (i.e an air-con specialist) or do you think the car should still go to a Porsche specialist?


Kwikfit use an automatic Machine which pulls and tries to hold a vacuum to check for leaks, doesn't always catch small leaks But it's not bad. Depends where in Derbyshire you are, Loe bank motors in bury are worth the trip as the guy who runs it is also an air-con specialist as well as a Porsche specialist and no more than an average mobile a\c outfit
http://www.loebankmotors.co.uk/
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
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Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Apr 15, 2019 7:12 pm    Post subject: Reply with quote

deMort wrote:
I was interested to know how you get all the pag oil out with an A/C service thats all .. new one on me and always interested in tips Wink


Discussed this with my mechanic a while back: http://911uk.com/viewtopic.php?t=121816
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deMort
Long Beach


Joined: 21 Mar 2015
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PostPosted: Mon Apr 15, 2019 7:41 pm    Post subject: Reply with quote

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 .
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Paynewright
Monza


Joined: 17 Apr 2018
Posts: 174
Location: Nr Lutterworth Leics


PostPosted: Mon Apr 15, 2019 10:24 pm    Post subject: Reply with quote

I’m sure I read that the compressor is the same as one used on an audi?
 
  
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coopertrooper2001
Monza


Joined: 07 Oct 2013
Posts: 168



PostPosted: Wed Apr 17, 2019 12:08 pm    Post subject: Reply with quote

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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