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iceboy Nürburgring

Joined: 18 Apr 2013 Posts: 375 Location: Berkshire
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Posted: Wed May 25, 2016 7:38 am Post subject: 996.1 Carrera 2 - Engine whine identified !?
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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
 _________________ Current cars:
996 Turbo S - Coupe/Manual
996.1 Carrera 2 - Couple/Manual
Mercedes S320 CDI - Every day car
BMW 320d M-Sport Plus - Mrs. Ice
VW Golf GTI 8v Big bumper - Summer Toy
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Gareth64 Silverstone
Joined: 20 Mar 2016 Posts: 138 Location: United Kingdom
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Posted: Wed May 25, 2016 8:01 am Post subject:
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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. _________________ 2004 996 Turbo
Basalt Black
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Avon Trainee
Joined: 12 Mar 2016 Posts: 79
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Posted: Wed May 25, 2016 8:17 am Post subject:
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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 Nürburgring

Joined: 18 Apr 2013 Posts: 375 Location: Berkshire
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Posted: Wed May 25, 2016 8:23 am Post subject:
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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 _________________ Current cars:
996 Turbo S - Coupe/Manual
996.1 Carrera 2 - Couple/Manual
Mercedes S320 CDI - Every day car
BMW 320d M-Sport Plus - Mrs. Ice
VW Golf GTI 8v Big bumper - Summer Toy
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Gareth64 Silverstone
Joined: 20 Mar 2016 Posts: 138 Location: United Kingdom
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Posted: Wed May 25, 2016 8:29 am Post subject:
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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? _________________ 2004 996 Turbo
Basalt Black
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Avon Trainee
Joined: 12 Mar 2016 Posts: 79
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Posted: Wed May 25, 2016 10:14 am Post subject:
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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 Dijon

Joined: 21 Mar 2015 Posts: 7581 Location: Brighton
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Posted: Wed May 25, 2016 6:59 pm Post subject:
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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: 3588 Location: Harrogate
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Posted: Wed May 25, 2016 7:05 pm Post subject:
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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? _________________ 2006 Cayman S PCCB's
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deMort Dijon

Joined: 21 Mar 2015 Posts: 7581 Location: Brighton
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Posted: Wed May 25, 2016 7:09 pm Post subject:
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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
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Chris_in_the_UK Estoril

Joined: 19 Mar 2014 Posts: 3588 Location: Harrogate
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Posted: Wed May 25, 2016 7:19 pm Post subject:
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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  |
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 _________________ 2006 Cayman S PCCB's
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Pickse Spa-Francorchamps

Joined: 20 Jul 2013 Posts: 366 Location: Fleet, Hants
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Posted: Wed May 25, 2016 7:57 pm Post subject:
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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  |
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. _________________ Pickse
-----------------
03 Arctic Silver 996T Tip S
Now 9E38 - An improved! 996T
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Harvster Trainee
Joined: 08 Jan 2019 Posts: 65 Location: Derbyshire
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Posted: Mon Apr 15, 2019 2:30 pm Post subject:
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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? _________________ Porsche 911 996 4S 2003
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Robertb Dijon

Joined: 01 Sep 2003 Posts: 7313 Location: South Oxfordshire
2002 Porsche 996 Carrera 4S
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Posted: Mon Apr 15, 2019 2:54 pm Post subject:
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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. _________________ "911- the guilt-free supercar"
Current: 2003 C4S Coupe, seal/black
Ex: '02 C4S Coupe, '96 993 Targa, '88 Carrera Sport Coupe
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maldren Suzuka
Joined: 07 Oct 2016 Posts: 1196
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Posted: Mon Apr 15, 2019 4:41 pm Post subject:
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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. _________________ Mike
2003 996.2 C2 Coupe Arctic Silver
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asterix_the_gaul Barcelona

Joined: 20 Dec 2008 Posts: 1284 Location: Cheshire
1999 Porsche 996 Carrera 2
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Posted: Mon Apr 15, 2019 6:52 pm Post subject:
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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/ _________________ 1992 944 S2 Cabriolet, Cobalt Blue/Classic grey -gone!
1995 993 C2 Cabriolet, Midnight Blue/Marble grey -gone!
1999 996 C2 Coupe, Ocean Blue/Graphite grey
2002 E46 M3 Cabriolet, Laguna seca blue/LSB
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Alex Le Mans


Joined: 06 Mar 2014 Posts: 17138 Location: The Ribble Valley, Lancashire
2000 Porsche 996 Carrera 4
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Posted: Mon Apr 15, 2019 7:12 pm Post subject:
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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  |
Discussed this with my mechanic a while back: http://911uk.com/viewtopic.php?t=121816 _________________ 2000 Manual 996 C4 Arctic Silver Convertible
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deMort Dijon

Joined: 21 Mar 2015 Posts: 7581 Location: Brighton
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Posted: Mon Apr 15, 2019 7:41 pm Post subject:
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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 . _________________ .
My Daughter's Crowdfunding has hit the target .
Thank you all so Very much .
She's not going until july 2020 though .
7pm - 9pm
Now At An Indy.
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Paynewright Monza
Joined: 17 Apr 2018 Posts: 204 Location: Nr Lutterworth Leics
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Posted: Mon Apr 15, 2019 10:24 pm Post subject:
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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: 172
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Posted: Wed Apr 17, 2019 12:08 pm Post subject:
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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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