Engine noise, thinking timing chain

[Tommylee1282]

So my 99 Xlt 4.0 sohc just started making this noise, I was hoping it's not the rear timing chain flapping around. What do you guys think? The video starts on the passenger side by the first spark and moves toward the pcv valve. So far I'm thinking all I can do is replace the rear tensioner and try some sea foam. No issues with the truck driving and no check engine light.
https://m.youtube.com/watch?v=7flOHAN3iPQ

 

[Tech By Trade]

Pull the valve covers and find out.

 

[Dominic10309]

My 2000 XLT V8 had a similar sound. Go to your mechanic and see what he says. I brought mine to the mechanic and left it there and after 2 days he finally took the engine apart and the engine was gone. I had to buy another engine. Half of the cylinders looked liked that \/.

 

[Tommylee1282]

I put the new tensioner in engine ran for a bit sounded worse than died. I pulled the valve cover and confirmed a broken guide and the chain was so loose I could almost lift it off. So I'm switching everything I can onto my 98 explorer same engine but with 170k miles. What's worth switching? So far the IAC valves were different. Or parts that's won't be compatible?