Timing tensioner failed? (not guide)

[bigredscowboy]

Has anyone ever had a timing tensioner actually fail? On the way home last night (cold but not freezing), something knocked and then a rattling noise in the engine bay. I thought I had picked up a stick in the fan or something. 1/2 mile and I was home and popped the hood. The driver valve cover was cracked in the front. Got it off this morning and the less-than-2-year-old guide doesn't have a piece of plastic left on it. I cursed the plastic POS and later came back out with fresh eyes. There was a tiny metal ball, maybe 2mm in diameter up in the top of the head. That's when I started looking and realized that the moving part of the tension has separated and was logged in a hole between the head and block. This was an OEM Ford part (but the guide and chain were aftermarket). How did that happen?!

Edit: 2003 Ranger 4.0 SOHC with recent full timing chain replacement

 

[Anime]

The failure of the tensioner on the 4.0L SOHC is well documented, there have been lots of threads on it. The tensioner design just seems to be very weak and fragile, and just isn't as heavy-duty as it should be for the motor.

There is supposedly a newer style of tensioner that has six spring leaves instead of just the three of the earlier style. But the basic design still leaves a lot to be desired, at least for such a motor. One of the reasons the 4.0L OHV is more dependable.

 

[2000StreetRod]

forced it into position

As I recall you had a head to block alignment issue and had to force the cassette into position placing a lot of stress on the pivot.

You probably damaged it at that time which allowed the pivot pin to work it's way out of the guide. There should have been tighter tolerances for the head and block castings. A new member (apparently a shop mechanic) recently encountered the same problem and asked if anyone new which years and models have the problem. I think he pulled the head, installed the cassette and then reinstalled the head.