jcalhoun

Sorry if this has been addressed before. I have done a lot of searching and am at a loss at this point.

Car is stock 2003 6Speed with aftermarket DV's and BMC air filter. 23k Miles.

I am consistently hearing a howling noise that can be best described as air rushing through a pipe (kind of like when you blow air across a bottle opening). I think it is coming from the rear passenger side. This happens in 3rd-6th gear when the RPMs are in the 2700-2800 range and I am cruising with little throttle (no boost registering on the instrument panel).

I brought the car to the shop and the car was diagnosed with a faulty diverter valve, so I had them changed with aftermarket DV's. I also had the power steering reservoir changed as it was squealing. Still the sound continues. It is quite annoying because the howling sound is constant while under cruising RPMs.

Any other ideas of what I should look into? Thanks!

Also, sorry for the newbie TT question, but is it normal to hear a similar winding down/ air rushing out a pipe sound when exiting the hwy onto off-ramps even when the car is not showing boost?

Macster

Was the diagnosis of the faulty DV's based on the noise? If so the diagnosis is wrong and you need to take the car back -- if you still trust this place -- for a 2nd attempt at diagnosing of the noise.

If the DV's were replaced based on some other symptoms and you trust this place take the car back and have the source of the noise id'd and fixed.

I'm unfamiliar with the aftermarket air filter setup. Custom air box? Possible installation issue?

Really the best person to hear the noise is an experienced/qualified Porsche tech. Get one in the car behind the wheel or in the passenger's seat and demo the noise. From the circumstances I suspect he'll have a good idea.

My idea? Well, no noise under boost. No noise at idle. No other untoward engine behavior. No CEL. No idea.

Seriously again, maybe the noise is not engine related?

Noises are sometimes tricky. They sound like they come from one place but they come from another.

Is this wind noise per chance? Can you have a passenger press against the passenger door side glass to see if this affects the noise?

What about the front hood? Its leading edge should be *below* the front bumper cover top edge some noticable amount. Be sure the gas cap filler lid is secure.

Yet another source of noise can be a radiator fan. My Turbo's fans are quiet, but once in a while when I turn on the Boxster's A/C and the radiator fans come on there's a hint of a faint howl from what I suspect is one or both fan motors. This howl is short lived and the fans make no noise at any other times and I can hear (faintly) them come on and go off as the coolant temp rises/falls so I have not yet felt a need to have anything done about the radiator fans.

Check under the car -- best done on a lift -- for any loose/damaged under body panels. I had a wheel well liner come asunder and its leading edge drag on the pavement only at speed (from air resistance) which made for an interesting few hours of running on the freeway until I finally pulled off into a large well lit parking lot and got on the ground with a bright flash light and spotted the signs the now in place wheel well liner had been dragging on the pavement. A few strips of duct later I was on my way.

While under the car check the condition of the CV boots, front and rear. Check for any excessive play of the cardan shaft. Check for any excessive play of any of the half-shafts.

Look for a loose exhaust system or a loose heat shield.

Another time I made a 140 mile detour to the OKC Porsche dealer for sure my car had at least one bad wheel bearing only to have the howling noise at 75mph and higher diagnosed as front wheel alignment issues. The tires were howling and it was clear from the tread's surface texture the tires were not tracking right at all. The alignment was not out that much either for the tech said no need to have the alignment done it could wait until I replaced the tires.

Admittedly a bit skeptical about this I drove nearly 2K miles home and arrived with the tires still in pretty good shape. After an alignment -- which the tech tried to talk me out of saying that it could wait until time to replace the tires and besides with worn tires he was not able to guarantee the results would be to his usual (quite high too) standards -- the noise was greatly reduced.

Residual nose coming from the fact the tires were now contacting the road differently (from the alignment changes) and were scrubbing in once more accounting for this. The alignment felt pretty good too.

I can tell you other than a bit of fleeting tire noise arising from the tire tread interaction with the road surface my Turbo makes no abnormal noise going down the road or at any other time.

I have to qualify the above though with the admission the as the tires wear/get harder from heat cycling they can make a bit of a racket at other times and at some point all the time. This is normal based on my experience with going through 10 or 12 tires on my Turbo over the nearly 90K miles I've driven it and uncounted numbers of tires for my Boxster over the last 260K miles. Some brands of tires (Pirelli is my experience) are worse than others (Michelin seem particularly quiet). Continental and Bridgestone (currently on the Turbo) are not as loud as the Pirelli but not as quiet as the Michelin tires.

The only times my car has has made any abnormal noise is once when what proved to be an idler roller bearing was noisy, and again when a power steering valve would make a high pitched squeal once the power steering fluid was hot.

Sincerely,

Macster.

crazyfrog

Get a pressure test done first .