The infamous 4.0 timing chain issue

[roboman]

The '99 4.0 SOHC was bought brand new by my parents in 1999 and was handed down to me a few years ago. Under hard acceleration, there's always been a slight rattle as far back as 2004ish that I can remember. Therefore, the tensioner or whatever (excuse my possible ignorance - I'm not completely knowledgeable about all car organs) has been busted for 6+ years but we've had zero issues with the engine. In the last couple months though, it seems like the noise has increased and it happens at lower rpms than what it used to. The rattle calms down a little bit once the car is warmed up though.

If the Explorer needs any big $ repairs, then I'm likely just going to sell it and look for a newer used vehicle, so I don't want to take the truck in to have the engine pulled and all the necessary things replaced. So my question is, what could happen since the timing chain components aren't all healthy? What would it take (driving wise) to completely ruin the engine because of this issue? Is it comparable to a timing belt in a different engine breaking and causing the engine to rev out of control? So do I just need to stay away from high rpms or what to prolong the life of the truck?

I know I asked a lot of questions, but those are the general things I'm looking for. Thanks for any input.

 

[dmwebb34]

One possible outcome.

http://www.youtube.com/watch?v=aUkXriHjQeI

It would be a shame to have it happen while driving.

 

[janolsson]

invest in doing the 00m12 kit (search will yield loads of info) $50 in parts if you do it yourself or 1 hours work for a mech that knows what he/she doing. Also oil flush with new filter and some 5 w 30 synthetic.
If that doesn't quiet it down then you are looking at probably front primary chain tensioner and front cassette both can be done without pulling the engine.

 

[Danson]

i am not really a mechanic, i can do some thing but i ripped apart the front of my engine and replaced the jack shaft and the balance shaft tensioners and guides and had to issues, it is very time consuming but is very doable

 

[roboman]

That's my issue - I'd LOVE to try this project since it sounds doable if you have common sense which I do. But the time consuming thing isn't good. I'm still in school and even after school, I have to run my siblings around for their practices every day. I just wouldn't have the time to do it in one straight shot since I don't always have access to another vehicle.