Engine Knock in LX470??? No Way (1 Viewer)

[tpham18nm]

Hoping you guys can give me some insight on what's going on with my Lexus. This vehicle is a 1998, LX470, with 176,000 miles, a fresh oil change 1000 miles ago, oil isn't low. It just happened this morning on a cold start. It quiets down after warming up but I can still hear it. Doesn't make a difference if AC is on or off. Rhymthic and increases with the RPMs of the engine. It sounds like it is from the belt/fan area. Recent history shows a new serpentine belt and fan clutch.



Really worried...

 

[nissanh]

remove the belt. Engine off, spin the idler, fan pully, A/C pully and tensionr bearings and listen. It looks like a worn out bearing.

 

[Biga27110]

doesnt sound like knock

 

[TheBussman]

are the fan nuts tight?

 

[Patron100LC]

Not a bottom end knock, sounds like it happens every 720deg, a loose plug?

 

[tpham18nm]

I went ahead and replaced the tensioner pulley, the old one was shot. I should have replaced the idler pulley as well because that one has a slight squeak to it also. I just heard it this afternoon when I turned the truck on. I believe that they were both worn. The idler pulley just spins without resistance and the tensioner was more wobbly than usual. I think this fixed the problem. Thank you.