Sucking noise and rattle whenever I accelerate hard at mid revs

[Neo]

I noticed yesterday suddenly that a noise is coming from the engine area every time I hit the accelerator while above ~3000 rpm. It tends to be more pronounced in second gear and happens in third and fourth, but not so much first or fifth.

The noise is like a short sucking noise at the moment I press the accelerator, like air being pushed out of or sucked into something, but it only happens if I accelerate hard while above about 3000 rpm. Sometimes, I hear a slight rattle as well. It's a little worrying (fortunately, I have a warranty), but does anyone have any idea what this could be?

 

[Buddy]

Best check the servicing covers top and front of engine bay to make sure they are secure and if they are remove them to see if anything is misplaced try running the engine without the covers fitted and blipping the throttle. You may hear the sound without the engine being under load. Favourite is a possible intake leak such as a sensor or pressure measurement connection slipped out or broken off but with all of the insulation around the engine bay doubtful you'd hear it unless the covers were loose. Since you have the warranty, why not go to the OPC?

 

[Wallachie]

I hear a sucking noise on mine too, but only when opening the throttle hard from low revs, it's obviously the engine sucking in air. I assume this is normal, i's a sound just like my mate's Gallardo made.

 

[Neo]

My warranty is a third-party warranty and only covers up to £80 per hour labour, so I wish to avoid the OPC if possible per [link=http://www.porscheclubgbforum.com/fb.asp?m=654906]here[/link]. Tried it again last night, and it tends to happen at ~2000 rpm or above. It definitely only started two days ago and, coupled with the occasional rattle that started at the same time, I don't think it's normal like a Gallardo at all! lol

 

[Buddy]

Have you tried it with the cover off? Possibly a hose clip on the intake could have come loose and be rattling against something, may even account for the sucking noise if say the hose isn't a good fit, you haven't mentioned if power is down or anything performance related.

 

[berty987]

The cayman and boxster use two resonator flaps in the inlet, these are actuated around 3000 rpm. If one of the connecting hoses become loose that link the manifolds to the resonator cross tube/ intake throttle body you can get a loud sucking noise when the resonator flap changes position. When the seal becomes very poor , the car idles unevenly. Worth checking that all the hoses on the intake system are secure and that the vacuum lines that go to the actuators from the small grey solenoids are also in place.

 

[Neo]

I had Tower Porsche take a quick look at this today while it was in for [link=http://www.porscheclubgbforum.com/tm.asp?m=663470]another repair[/link] (gear linkage replacement), and he said the engine sounds normal and that it may have been that this resonator flap was stuck before I started hearing the sucking noise and he said this is normal for cars that have been sat around on a forecourt for weeks or months, but usually frees itself up after a month or so of driving and this is probably why I can hear it again. And he said the reason for it is because Porsche spend a lot of money on the sound inside a car and this sound is deliberate to show that induction is taking place. I think he was talking about the same thing as you berty987 as he said it actuates at around 2500 rpm. To be honest, I have no idea about any of this and I don't know whether it's right or wrong, but I still feel that the noise is a bit too strange to be deliberate.

 

[Buddy]

If you have any friends with a Cayman or Boxster see if they will either take you out in theirs or ride with you so that they can listen. I have the Chrono Pack with a standard exhaust, if I had the sports exhaust it should make more noise when chrono is activated but funnily enough it does and it's even been commented on by others. Must admit, I haven't taken a look to check but sports exhaust isn't on the options.

 

[Wallachie]

Do you find the engine gets louder just over 5k revs?

 

[Buddy]

Yes in both modes but it's much louder right through the range from just above 3K in sport setting. It really sings in sport, addictive in fact.[] I took Paul from PH for a spin when I first got it, he's been dealing in Porsches for about 15 years and even he asked "is it a sports exhaust?"

 

[barrie nunn]

induction rawwwwwwwwwwwww