I have a 2007 Ford Explorer sport trac 4.0 engine- everytime I start it I hear thumping noises- especially after I turn the heater on. After awhile it goes of- it sounds like something isnt opening or closing bthe right way.
That's going to be one of the actuators for the HVAC system that controls the air doors for mode and temperature. You have both vacuum and electric but the noise sounds like a vacuum actuator that is leaking vacuum somewhere.
I have the same problem on my 98 chevy suburban v8 5.7 would this be the same thing that is worng with mine?
If you need help with something you need to start a new question of your own, not hijack this one.