'06 5.4 Triton Engine Bay Rattle
 

Hello,

I have a 2006 F150 with the 5.4L Triton, about 150k miles. I am experiencing a loud rattle/tapping noise, and it sounds like its coming from something rotating. The noise is present at idle, when in gear, and when accelerating. The rattling quickens through acceleration as if matching RPMs. Within the last 1,000 miles I have had the spark plugs replaced (kept old ignition coils), a new tensioner pulley, and a new belt. The sound seems to come from between the belt/pulley area and the radiator fan.

Under the hood it sounds like the radiator fan blades are tapping up against something; it is very loud even from inside the cab when running. Again, the rattle quickens when accelerating, so I would suspect something along the belt line like a pulley, but could a bad pulley or pulley bearing produce such a rattle/tapping noise instead of a whining noise?

I suspected the fan so much I am looking into replacing the fan clutch, but I cannot find any evidence to support a failing fan clutch would produce a rattle/tapping noise. EDIT: The sound is definitely within the engine bay, and it sounds external in a sense that the noise is coming from something not covered or from inside the block. Like a baseball card on a bicycle wheel.

The only non-Ford part under the hood is a K&N 57-2556 cold air intake system. I point this out because from a visual standpoint while the engine is running, there is a good level of vibration about the block, and the intake line vibrates a good amount. This vibration can be seen, but does not seem to match up to the frequency (and honestly decibel level) of the rattle/tapping noise.

Any thoughts? I have convinced myself to look towards the fan, but no ailments of failing fan clutch examples seem to match this sound. Should I be looking to tighten something down like the radiator shroud? Thank you everyone in advance.

sounds like the old fashioned cam phaser rattle or a blown exhaust manifold gasket

1) All the extra crap getting sucked through that K&N isn't doing your engine any favors. The cold air intake is actually anything but.

2) Use a long bar or screwdriver on the passenger side valve cover, and you'll probably hear your frozen cam follower most easily. You want to take both valve covers off to check for said frozen/worn cam followers before it eats one and costs you an engine.

3) Time for a full timing job, including VVT solenoids in your case.