My wifes 2008 Explorer Eddie Bauer edition has the 4.0 V-6 engine and we have a similar noise to what CA stated up above in post 53. The engine is quiet when we start it up but when we give it gas, we notice the noise that sounds like marbles in a metal coffee can being shaken. The noise is only present between 2000-3000 rpms. The noise is more noticeable when giving it gas at more rpms when the engine is cold but after the engine warms up, it seems to completely disappear sometimes. Most of the time it likes that 2500-3000 rpm range to have the noise when under light throttle, even under a load going up a hill.

Does this sound something like what a guide / tensioner issues would be? From what I have read up on, it is primarily noisy when it first starts up and at idle which ours does not do. Our car now has 106,000 miles on it and of course is out of warranty. We are taking it tomorrow on a long trip and I'd like to have a piece of mind that the engine isn't going to give out on us a long ways away from home.

On a side note, the top plastic tank on the radiator I noticed is starting to crack outward. Almost like there is too much pressure inside the radiator. The cracks are straight across where the reinforcing ribbing is too, in two spots. (one spot on each reinforcing rib in the center of the rad.)

Also, is there a way to tell if it could be the internal part of a catalytic converter rattling vs. the timing chain tensioners?

 

I know this is an old thread, but... click here for a detailed write up
on changing the Left+Right OilPressurized TimingTensioners in the
1997~2011 Ford V6~4.0L~SOHC Engine as part of a 75k~100kMile PreventativeMaintenance routine;
the original weak design of these Tensioners is a root cause of TimingGuide failures in many early SOHC engines.