Hi every one I'm looking to buy a 2001 f150 I have test drove and listened to the noise the truck has around 150000 miles on it it has no power loss and drives great but just for my peace of mind I would like to know ur guys opinions on it it will help me decide if I will buy the truck or not the sound is hardly noticeable when u first start the truck after it warms up u can hear it If the hood is open and it is never constant on the sound it's in the upper part of the motor passenger side please let me know what u guys think

 

Sometimes the tapping sound can come from a loose spark plug, they can blow out if left loose. It may become more or less noticeable as it warms up.

 

If it have variable valve timing, it is your cam phasers... VERY expensive! Or, maybe exhaust manifold. Maybe pick up a cheap stethoscope at a parts store so you can pin-point it.

 

I started two threads on the matter, two trucks, one was a knock sensor causing timing to go haywire when cold, and the other was worn out cam journals.