Vacuum leak inside of cabin

[Cole931]

Hey everybody!

I just bought my first jeep for a hunting/fishing/camping vehicle (and maybe some light off-roading in the future). It's a high mileage 2001 Cherokee sport. i have an interesting issue I discovered. At highway speed when I let off of the accelerator I get a whistling sound from the drivers side dash/footwell area. I saw a post about a vacuum valve for cruise, but I can't seem to locate one on my pedal. Cruise control light will come on but the cruise won't engage as well and I was thinking that they were related but now that I can't find a switch I'm not so sure. any input would be appreciated, and thanks for your time!

 

[Saudade]

Check inside the engine bay. Whistle on "off throttle" is typically a vacuum leak. The only vacuum inside the cab is for HVAC vent controls. There is a vacuum reservoir behind the front bumper, passenger side. A vacuum line runs under the battery.

Does it whistle in park/neutral or only under load?

 

[Unclewolverine]

All vacuum for the cruise is under hood, passenger side near the battery I believe, but a vacuum leak is most likely why it doesn't work. Saudade is right, only hvac is vacuum in the cabin. Do your vents switch?

 

[lawsoncl]

I saw a post about a vacuum valve for cruise, but I can't seem to locate one on my pedal.

That would be for the much older Jeeps. Not present on a 2001.

 

[Cole931]

Vents seem to work correctly, but the sound is definitely inside of the cabin that I'm hearing. Maybe I'll disconnect and cap the vacuum to the heater controls temporarily and see if that gets me anywhere.

 

[Cole931]

Check inside the engine bay. Whistle on "off throttle" is typically a vacuum leak. The only vacuum inside the cab is for HVAC vent controls. There is a vacuum reservoir behind the front bumper, passenger side. A vacuum line runs under the battery.

Does it whistle in park/neutral or only under load?

Only at highway speed with the throttle cut (engine braking)

 

[RCP Phx]

How do the brakes feel? Also check the throttle body shaft/bushing.

 

[Cole931]

How do the brakes feel? Also check the throttle body shaft/bushing.

Yeah that's probably one of the next things, brakes feel squishy at the beginning of travel until i hit the wall where they start to engage. Maybe brake booster on the other side of the firewall and I'm hearing it through the firewall? I'll give that a look tonight.

 

[Ahvicha]

i dont mean to be that guy but by whistling, maybe you're talking about power steering issues? they make a interesting sound when they start to go out. but again that only happens really when turning. im not sure but i thought it might be worth a shot at least noting

 

[Tim_MN]

The climate control switch and associated flapper valve that changes the air output to the floor/dash vents/defrost is vacuum operated. A vacuum leak will make it default to defrost. Next time you hear the noise, check if the airflow is at the defrost vents.