2002 Ford Explorer

Noises problem
2002 Ford Explorer V8 Four Wheel Drive Automatic 104,000 miles

Passenger side of dash has a hissing noise that continues when engine is running. When the accelerator pedal is pressed and car speeds up, it stops for a short time, then returns. What is this?
November 28, 2008.

Sounds like you have a leaking vacuum pipe on the heater controls

Heater Control Valve
The heater control valve is actuated by the heater control valve vacuum switch, if equipped (manual climate control), the recirculation door vacuum circuit (manual climate control) or the heater control valve vacuum control circuit (DATC). When the heater control valve is closed (full vacuum), coolant flow through the heater core is shut off and A/C cooling efficiency is increased.

Dave H
Nov 28, 2008.