I have a 2001 XJ sport and I’ve had this really loud, really annoying whistling sound for a few months now. The sound starts up after a few minutes of driving. It goes away as soon as I’m accelerating or giving it enough gas, but if I’m just cruising or stopped at a light it’s as loud as a whistle.

I’ve checked a little around my vacuum lines and replaced a few connectors that were dry rotted or had cracks. I replaced the grommets and elbow connectors going into the valve cover (which stopped the sound for a day). I replaced the throttle body gasket and cleaned out the TB. Still this whistle is killing me.

I have a mechanic friend who suggested replacing the intake manifold and gasket because it sounds like it’s coming from somewhere near the intake manifold or air box. Im hoping I don’t have to do a big job like that. It’s really hard to tell for certain where it is though because it’s so loud.

Please help!

 

Yup, sounds like a vacuum leak

 

Mechanic's stethoscope.

 

I've had this happen to me. Check your brake booster, there's a fitting that tends to crack, is connected to the intake via a hose..