Squealing sound coming from engine compartment

[boxstersrule]

I have a squealing sound coming from the engine compartment.

When the car is started from cold there is no noise. After approx 15 min of driving (car up to normal operating temp 180-190) the squealing starts barely noticeable at first. It seems to start when at constant load or decreasing throttle and application of throttle will cause noise to stop. If I continue driving the squeal intensity increases until it is always there regardless of throttle position (it still changes in pitch and intensity with engine load/rpm just doesn't stop).

The squeal is present when moving and when stopped at idle so I believe this rules out wheel bearings/brakes. Also, squeal is not affected by clutch position, engaged/disengaged.

I have replaced the idler pulleys and the belt tensioner and the belt itself. This did not solve the problem and I am out of ideas. I know that one other person has had this problem, but there was no post on what the problem ended up being.

The car still runs well with no noticeable loss of power even when noise is present. Car idle is good, oil and coolant levels normal, and no fault lights are on.

Car is a 1998 with 121k miles. I am out of ideas on what to check. Looking for suggestions. HELP!!

Thanks,

Paula

Edited August 11, 2008 by boxstersrule

[PAULSPEED]

Try spraying wd40 on each pulley shaft. Might help

in your search. My guess is one of your pulley shafts is out

of greese.

Paul

[Loren]

Check the polyrib belt pulleys, and water pump.

[Glyn]

Now you wont believe this!!, without doubt this is the Air/Oil seperator, told you you wouldnt believe it.

This is the valve inside the AOS and only emits the noise when on overrun in the early stages of failure, open the throttle and it goes away, at idle it sounds like the idler bearing squeeking.

[boxstersrule]

Now you wont believe this!!, without doubt this is the Air/Oil seperator, told you you wouldnt believe it.

This is the valve inside the AOS and only emits the noise when on overrun in the early stages of failure, open the throttle and it goes away, at idle it sounds like the idler bearing squeeking.

At this point I would probably believe anything and I trust what you are saying, but I have to ask, how do you know that it is the Air/Oil seperator? Have you had this problem before and replaced the air/oil separator and had the problem go away?

[Glyn]

Now you wont believe this!!, without doubt this is the Air/Oil seperator, told you you wouldnt believe it.

This is the valve inside the AOS and only emits the noise when on overrun in the early stages of failure, open the throttle and it goes away, at idle it sounds like the idler bearing squeeking.

At this point I would probably believe anything and I trust what you are saying, but I have to ask, how do you know that it is the Air/Oil seperator? Have you had this problem before and replaced the air/oil separator and had the problem go away?

2 weeks ago i went from the UK to Germany to get on the Nurbergring, Got to the ferry point and the car was emmiting a squeeking skweal sort of sound just like fan belts do sometimes, thought it was the car behind me and only realised it was mine when i pulled away, loaded on the ferry, switched off, thought nothing more than a dry pully wheel - i would change it when i got back, started up after the two hour ferry crossing and it had all gone away - confirmed in my mind it was the idler pully.

On the way to Germany stopped off at Brugge, getting back on the motorway i noticed i had a slight squeel back but strangly only on the overrun, light throttle and it went completely, i had another 170ish miles to go so carried on, the noise got worse, much worse, embarrassingly so, thought all the other cars would be hearing it too, but a little throttle and away it went.

Now it didnt go immediately like a light bulb does when you turn it off it sort of reduced in volume immediately then dissapeared over what may have only been two seconds but this fade was obvious, Stopped for fuel, restarted - gone again.

Cleared the rest of the miles and had entered the town the hotel was at, pulled away from traffic lights and clouds of blue smoke.

Long and short of it is, Porsche picked up the car, took it to Bonn, analysed the car and announced the air/oil seperator, gave the go ahead for the work to be done.

Expected on collection of the car that i would need to do the squeel job later, drove the 450 miles home, and drove it hard - not a jot of a sound out of it.

The only part changed was the seperator.

Clearly the noise was generated by vaccum and this dissapears when the throttle is opened as the valve open to allow the induction to suck the internal gasses away and burns them

[boxstersrule]

Now you wont believe this!!, without doubt this is the Air/Oil seperator, told you you wouldnt believe it.

This is the valve inside the AOS and only emits the noise when on overrun in the early stages of failure, open the throttle and it goes away, at idle it sounds like the idler bearing squeeking.

At this point I would probably believe anything and I trust what you are saying, but I have to ask, how do you know that it is the Air/Oil seperator? Have you had this problem before and replaced the air/oil separator and had the problem go away?

2 weeks ago i went from the UK to Germany to get on the Nurbergring, Got to the ferry point and the car was emmiting a squeeking skweal sort of sound just like fan belts do sometimes, thought it was the car behind me and only realised it was mine when i pulled away, loaded on the ferry, switched off, thought nothing more than a dry pully wheel - i would change it when i got back, started up after the two hour ferry crossing and it had all gone away - confirmed in my mind it was the idler pully.

On the way to Germany stopped off at Brugge, getting back on the motorway i noticed i had a slight squeel back but strangly only on the overrun, light throttle and it went completely, i had another 170ish miles to go so carried on, the noise got worse, much worse, embarrassingly so, thought all the other cars would be hearing it too, but a little throttle and away it went.

Now it didnt go immediately like a light bulb does when you turn it off it sort of reduced in volume immediately then dissapeared over what may have only been two seconds but this fade was obvious, Stopped for fuel, restarted - gone again.

Cleared the rest of the miles and had entered the town the hotel was at, pulled away from traffic lights and clouds of blue smoke.

Long and short of it is, Porsche picked up the car, took it to Bonn, analysed the car and announced the air/oil seperator, gave the go ahead for the work to be done.

Expected on collection of the car that i would need to do the squeel job later, drove the 450 miles home, and drove it hard - not a jot of a sound out of it.

The only part changed was the seperator.

Clearly the noise was generated by vaccum and this dissapears when the throttle is opened as the valve open to allow the induction to suck the internal gasses away and burns them

Thank you so much for the information. And you are right, it is embarrasing to have your Porche make this kind of noise. I really do thank you for the information about this problem. I was at wits end about what it could be. I have a call in to the Porche dealer to get an appointment for service. This is not a job that I should probably tackle myself.

Paula

[sc00ter18]

I had the same issue 2 months ago.

replaced the AOS and it went away.

Just to give you heads up, your car will puff smoke after replacing the AOS for a few days or even couple of weeks.

Dont stress over it , its normal

Good luck

p.s i would not recommend a DIY

Edited August 11, 2008 by sc00ter18

[boxstersrule]

It is at the Porche service department right now waiting for the parts to come in to fix it. I will attempt to do some repairs myself, but this was not one that I was willing to do. And everyone that said it was the AOS was correct. Thanks for the advice. I really appreciate it.

[shihman]

Check the polyrib belt pulleys, and water pump.

hey guys, mine boxster is a 2000 S and i just experienced a similar problem except that my smoke comes out of the right (passenger) side vent and after i parked, there was a leak in the mid section towards back under the car. the puddle seems to be water. could this be both the AOS and the water pump? please help. thank you all.

[Beelzy]

Hello Shihman,

Sounds like the water pump or related tubing connecting the system. Time to crack the cowl and take a peek.