Ok, I have an 2007 4.6 v-8. A few months ago while hauling a trailer of material my truck just shut down form over heating. Wouldn't even crank until it cooled down. I noticed once I cranked it back up it had this tapping noise that it didn't have before. Found out later that the over-heating was from a clogged oil screen. I've noticed since I got it back on the road that the tapping would quiet down after the truck warmed up but it was still audible no doubt. Lately though I've notice that even after warm up it has more of a "slapping" noise now. At times if the idol is at a higher RPM its more the tapping, but when RPMs are a little lower at idol it turns to a slapping.
I get head at all angles under the hood and under the truck and its really hard to figure out where the sound is actually coming from. Could this be the timing chain slapping. Or is it a lifter, or what. Its driving me nuts.

PS: One more bit of info: Eng light is intermittent on/off. Had AutoZone do a check and it signaled #5 cylinder issue, noting possible miss-fire. Changed plugs and coil. Still get the engine light intermittent off/on. Don't know if that has anything to do with it but thought I'd mention it.
Thanks for any help you all can provide - greatly appreciated!

 

Impossible to diagnose a noise over the internet. However, overheating due to a clogged oil screen probably means you'll be looking for a new engine soon. The noise could be almost anything with an oil starved engine. Good luck hope it doesn't cost you too much.

 

Well, I've been running the truck everyday since the over-heat for about 8 months now. It runs fine. It just has this clacking noise.

 

Just kinda wondered if an auto stethoscope would be able to pinpoint where the noise actually is.

 

Does the 4.6 engine have cam phasers or is it just the 5.4?

 

Only the 3V 4.6 had phasers, and that engine was never in a F-150. Your 4.6 doesn't have them.

 

Correction, I meant to say only the 4.6 from 2009+ had the option of a 3V (and hence phasers) in the F-150.

 

Ok. Think the issue has been figured out. After doing a compression check on all cylinders, 2 of them are at around 120 and 125. The others are between 145 and 155. So it appears now that the noise is most probably gap wear in the valve/valves. #1 and #8 are the culprits. I was told that this particular engine is rated for only 140,000 to 170,000 miles. I have 156,000 on mine. Long story short. New engine install.