Some knowledge needed please? I have a 2004 lariat 4x4 screw cab, awesome truck. In the last couple of weeks everytime I start the truck I have a squealing noise coming from the engine compartment that only last for about 5 to 10 seconds. It actually sounds like the belt, I checked the tension of the belt by touch and it felt fine. I have about 22,000 miles on it. One more thing. Everytime I engage my ac, I hear and feel a thump coming from the pasenger side lower dash area. No power loss or ac malfunction. If anyone can relate or help it would be apprieciated. Thanks!

 

The squeal is a common problem. Get a Gatorback accessory belt, it should stop the squeal.
The thump is probably just the passage to the air conditioner heat exchanger opening under the dash. The vent to the windshield is probably closing as well. They are vacuum actuated when the AC is engaged.