My wife has a 97 Expedition with 120,000 miles. It has a real bad "spark knock" when it is cold, but it goes away when the engine warms up. Someone told me that this engine has a hydraulic tensioner on the timing chain that may be slow to "tension" the belt until the engine warms. Does anyone know if this is true or have any experience with this sort of problem?

Thanks for any help.

 

yes they do have hydraulic tensioners,one for each chain

 

Are you certain that it's a spark knock, or could it be the piston slap issue found on a lot of triton v8's? Do a search on "piston slap" on this forum for more details.

 

A lot of people have eliminated "start up" noises by using the Motorcraft oil filter with the drain-back valve in the threaded end. Also, I would switch to 5w30 if you are using anything heavier like 10w30. You can probably find posts in the Oil and Lubrication forum on this.