Hello! I'm hoping that someone has the answer for me or perhaps an idea. There is a noise the mechanics cant find it because they don't have the the time to drive the car.

2004 XJR 90,000KM (56,000mi)

About the noise:

-Only when the car is in motion
-Doesn't change/modulate with REVs or Speed
-Sounds like a plastic bag is being dragged out side or a deep low hiss
-Seems to start once the car has reached temperature
-Sounds a bit like Morse code if you were to do it with a plastic bag out the window.
-It is NOT wind noise and sounds like it is on the left side of the engine/exhaust.
-I can't tell if it is the back or the front
-Doesn't go away when the car is shifted into Neutral
-Doesn't changed when you break ... only when you stop.
-Doesn't do it when parked or if the car is still even if you are Revving the engine.

I'm at my whits end! It sounds like a loud and intermittent and doesn't respond to speed or revs.

Any ideas? Exhaust? Belts/Bearings?

Thanks!!!

 

Forget the plastic bag... It sounds like a belt but rather than a squeal is is more of a gushing air noise.

 

Gushing air noise maybe air suspension pump or venting the air/pressure from the pump?

 

Hi Casper, I must say I don't think it is the air pump. When I'm at a stop the pump sometimes raises the car up and I can't hear a thing...

 

Mine have some of the noise when stepping on the brake while in motion and the car seems to vent some pressure air out and it's coming out from the left side of the front too. It sounds like blow off valve from turbo car. It's not the pump that makes the sound but it's some form of pressure relief from the air shock or something I guess.

 

Update: I removed the two fuses for the air suspension and the noise is still there... I drove the car to 60kph and put it in neutral and turned off the ignition while the car was moving and the noise was still there... Any thoughts?!?

 

You could have a leak in the power brake vacuum booster. There is an engine vacuum hose that connects to it and an internal air bladder, either of which could account for the noise.

 

You might have a loose caliper rubbing the disk , check the brakes for this or a rock in a caliper.

 

Thanks for the breaks idea. I'm confident it isn't the breaks because the noise is there even if the breaks are depressed. I thought it could be the park break caliper but it doesn't seem to be.

 

Could the noise be some sort of low break pad warning? The breaks sound good when applied but perhaps there is some sort of "warning devise" that makes a constant grinding noise while driving?

 

You can get a vacuum leak in this area even without brakes being applied. Start the engine, open the hood, remove master cylinder compartment cover and get your ear down close. Worth a try says I.

quote=DanielCR;432055]Thanks for the breaks idea. I'm confident it isn't the breaks because the noise is there even if the breaks are depressed. I thought it could be the park break caliper but it doesn't seem to be.[/quote]

 

If the caliper is loose and rubbing the disk, the brakes will still work but the caliper body will continue to rub the disk and make the noise until both bolts fall out! Then it will be a new experience as it rides forward until the hose breaks and it falls off!

 

...me thinks, it is a vacuum leak (disconnected or broken hose). These are extremely hard to find.

Good Luck!

 

I agree Road King.

 

I hope this helps anyone with the same issue. It is finally fixed! It turns out that the noise came from a plastic dust ring that came lose from the drive shaft bearing. Apparently it was spinning & rubbing and making the noise. The mechanic removed it and all is well.

 

Good to see it was fixed , thanks for your update