2004 4.0 sohc lifters clattering ONLY when hot???

[Zepplin454]

i have a 2004 explorer 4.0 sohc 115,172 VIN "K" engine built sept 18,2003. there is a clattering noise from inside the valve covers only when the engine is HOT. when the engine is cold there is no noise. no death rattle or lifter noises. just quiet 4.0. bought it with 59k. used 5w30 motorcraft oil till about 72k then switched to pennzoil platinum till about 90k then switched to pennzoil ultra. always used wix, motorcraft or purolator filters. strickly stuck to 5k OCI. drivetrain (engine,trans,diff,4x4,p/s,coolant, brake fluid, all O2's, plug, wires etc.)has been maintained well before the manual service intervals. truck hasnt broke down once. so as you can see i like to keep my truck running like a top. but this noise bothers me a little bit. its been doing it for about 1.5 yrs. but it doesnt do it all the time. usually when the engine is really hot. mainly during the summer because that the hottest time. anyone have any fixes or sugustions for me? oil additve? different oil weight? any useful help is welcome

 

[Hitchhikingmike]

Could you post a video of the sound? It is hard to diagnose your problem. Does it only make the sound at certain RPMs or at idle?

 

[Zepplin454]

ill try to get a video. but it does it at idle up to about 1300 rpm. sounds like its low on oil but its not. or the noise you get on a really cold morning when the oil is really thick and dry up top

 

[Hitchhikingmike]

Does your engine sound like mine?

(dead link)

This is a cold start. In the beginning you can hear that the engine is quiet. Snap to 3:07, when the engine is warm and you can hear sound from the heads.

 

[Zepplin454]

kinda. sounds like your is idle higher than mine but that could be the video