Odd situation with a SOHC Timing Chain.

[MtExplorer Guy]

Howdy guys,

2003 Explorer with a 2004 4.0 SOHC motor, motor has about 80,000 miles on it, when I start it up, sounds great, when it warms up, the front driver side chain rattle, I put a new tensioner is, figuring it was gone, the one I took out, I was not able to compress, it was all the way out and jammed, so I put a new one in, two weeks later, small rattle again, when warm, I just pulled the new one out and it was also jammed in the out position.

I just need confirmation, it seems as if the cassette is broken on the right hand side of the cassette that goes up to the drivers side cam, it would seem when you pull the tensioner, the cassette should move out to the hole the tensioner mounts in, am I right in my thinking?

Thanks for your help in advance.

 

[2000StreetRod]

no internal spring

There is no internal spring in the cassette guide assembly to make it expand against the tensioner.

The hydraulic tensioner applies pressure to the slack side of the cassette. The other side (traction) is kept taught by the jackshaft pulling the camshaft sprocket via the chain. However, I agree that the cassette guide is probably broken. The piston could not jam in the fully extended position otherwise. The guide was probably broken before you removed the first tensioner. The left guide should be metal reinforced on both sides since that has been done since the 2002 and later models.

The plastic protrusion that the piston presses against is probably broken off or slipped out of position because the plastic tabs that position the plastic guide chain wear surface have broken. You should be able to confirm that by removing the valve cover and inspecting.

 

[MtExplorer Guy]

Thank you for the reply, what is odd, is I can see into the hole the tensioner mounts in and see the plastic protrusion that the tensioner rides on and it seem to be in the correct position. I installed this engine because the original engine had rear cassettes that were broke and I went with a year newer to try and avoid the problems that has plagued these engines. I guess I struck out on that point, I am just surprised it went at 80K, I guess I will let it sit till spring and replace the front cassette.

Thanks again.

 

[2000StreetRod]

pivot bushing

Sometimes the pivot bushing separates from the guide assembly allowing the two sections to move out of position. Notice the difference between the pivot bushings in the first photo above. The top cassette is a Cloyes (Borg Warner) part and the lower cassette is a Ford OEM part. The Borg Warner bushing has a keeper while the OEM bushing is pressed flat and should never come out.