a56nomad

I have a 2004 F-150 with a 5.4 and 4 X 4, I have a noise that sounds like a dry drag then thump about 3 to 5 seconds after starting the motor. Most of the time after it has sat for over night. Sounds like it is coming from the passenger floor board. Wondering if the heater damper looses its vacuum and closes all the way, then when it gets the vacuum back, it slams open or back to its setting? Does anyone else have that same problem or noise right after cold start-up?
Thanks
A56nomad

lewissa81

The hvac in these trucks do not use vacuum to operate the mode/blend doors. They are controlled by electric motors.
Go through the hvac settings, and see if everything works the way it should.
You can also check the 4wd to see if the passenger iwe actuator is losing vacuum and locking in.
Other than those, I haven't a clue as to what the problem could be.