Strange moaning sound from rear when cold and at idle.

Hi everyone, I have a strange moaning sound that comes from the engine compartment at idle. I drive 12 miles to work every day. I get in the car and start it and there's no moaning sound. Drive away to work for the first half of the journey every time I come to traffic lights or stop the car starts to idle then comes this strange moaning sound, it lasts for about 1 second then goes away and can happen multiple times at one set of lights. I have noticed that the revs of the engine change slightly when this happens almost like somthing is switching on.. by the time I get to work the noise has stopped it then wont do it untill the next mornings journey. It's just been into Porsche for £3.000 worth of service and repairs but they couldnt find anything at all wrong. I've heared of things making a vacuam cleaner noise/ whine but not this sort of moaning sound. The cars away in the garage for winter and I would like to try and sort it out if i can. it's been doing it for about 4 months now.. Anyone every had or heared of this? Cheers A

whch 996 do you have?

Sounds like it might possibly be the aircon compressor to me. Next time its doing it turn the aircon off and see if it makes any difference. If it does then try having the aircon regassed with lubricant (it all has that now i think). Mine made the same groaning noise when it needed regassing....and so does my BM daily driver.

...+1 I'd say it's something to do with your aircon (if you're running it at the time of moaning...?). I'm no expert but it could be that the pressure is a bit on the low side and the pump is struggling a bit. Would you say that your aircon is working well? OPC did £3k worth of work??!! What the hell did you get for that?! Did it include a holiday in the Maldives!?

I find i sometimes get an irritating moaning sound too, but more from the passenger seat.... :sad:

WATER PUMP water pump maybe ?

Thanks for the reply's it's a 03 turbo the only thing is I run with the aircon off. but it does still make the noise when it's on also. I was thinking it might be power stearing pump. it does sound like something gets switched on tho before the noise happens then off again when it stops. i'm really not too sure without jumping out at the lights and sticking my head in there.. i'm sure that'll amuse people.. It's does go away when warm tho and only happens for half my journey to work in the mornings. it then wont do it untill the next morning.. if not then i've either got a cow in there or a ghost... Ye 3k major service was over a grand. found two cracked coils. need a new front rad. I had a few dents removed by a dent master guy.. I had my split arch trims replaced. front track rod ends were knackered so it need a geo check after they were done.. it soon adds up.. i know I could have got it done at another garage but another garage were the ones that crakced my side repeaters, cracked my inner arch trims. and scratched my front bumper also then denied it all when I told them.. i'd far sooner pay people that know what there doing than monkeys that think they do.. if anyone can put forward a good indy in the Edinburgh area i'm all ears.. : )

There is a pump that pushes oxygen into the exhaust for emissions purposes, may come on when cold or at certain times when required, pump is situated just underneath the oil filler pipe in a turbo set back and to the right of the pentosin reservoir could be this thats resonating through the exhaust when its activated let us know how you get on