Hey guys,

I hear a Hiss noise, thats pretty loud, sounds like its coming from my front end. I think its brake related, but not sure..

The hiss happens usually when I go above 40+ mph and a medium-low high throttle.. then disappears when full brake is applied..

(i have searched this in the forum but only found irrelevant posts thats for a different vehicle)

I have changed my rotors to drilled and slotted - stoptech
with ceramic pads..

I thought it was the pads, so i bought new OE pads, and took off my ceramics.. and the hiss is still present..


could it be my:
Booster? - but brakes are not stiff at all
brake rotor/disc?
Vacuum leak?


09 Prem Lux XF @ 95k

Very common to have a hissing type sound with drilled/slotted rotors. It's the sound of the air hissing across/through the vents and holes in the rotors themselves. I've experienced the same sound with 3 cars on which I've installed drilled/slotted rotors -- an Acura I used to own, my Alfa Romeo Spider, and my Jaguar XF. I'm betting the sound is especially audible when you drive in the left lane adjacent to a walled median -- the sound bounces off the wall and you hear it quite loudly when your window is down.

I somewhat agree, but..

Right when I hear the hiss, I try to eliminate it by completely stopping and it does go away, but if I dont stop all the way and reduce to 5-10mph, theres still faint hiss.. i dont think that air can still go through the holes and slots @ 10mph..

I got an appointment with the dealer in 2 weeks, and until then its a complete mystery. It aint my booster as it was checked recently.. and brakes are not hard at all.. Will update for future 'hiss' problems that others might experience.

Hi - any update on the hissing issue? I have the same problem that stops once brake is pressed. Thanks

Miracles do happen, but the original poster hasn't been around for a while:

Last Activity: 06-13-2016 06:17 PM

Good to know - thanks for the update. Hopefully, someone else might have some ideas

Latest update from the dealer is that this is 'servo hiss' which he says is perfectly normal. As the hiss is getting louder, this seems unlikely. Any one familiar with servo hiss?

Thanks