timing chain noise

[Harry Gene]

Hello my name is Harry Gene and I have a 1999 ford explorer 4liter sohc 4x4 I have a timing chain noise upper left corner only after it warms up what can it be

 

[Rick]

The timing chains are the weak spot of the SOHC engine. This link has a list of a ton of threads on the issues: http://www.google.com/cse?cx=002749...b=0&gsc.q=sohc timing chain issues&gsc.page=1

Here is a good thread on diagnosis and repair:
http://www.explorerforum.com/forums/showthread.php?t=287416