Hello,

Well, the timing chain had been quiet except for a few seconds on start-up. Now, its there most of the time-all of a sudden. Seems to quiet down at 1800 RPM or so.

Engine has 102,000 miles.

Pulled valve covers, chain looks tight, no slack. Local mechanic said it looks good also. Compression check is good in all cylinders.

Maybe replace hydraulic tensioners, they are original?

Checked exhaust, cats, they seem fine.

 

Mine has 114500 miles and mine are noticeable but that's the way it is on a 4.0 I guess.

 

The 4.0l SOHC had badly designed and poor material on the chain guides which caused them to deteriorate fairly quickly in some engines, so they got chain rattle noise.
Some switch to a 10w-50 oil to quiet it but that's all you are doing, it isn't "fixing it".

If a chain should slip/skip you could damage pistons and valves on one bank.
(I have read that 4.0l SOHC engine is non-interference, with 9.7:1 compression I don't believe that)

I think around '04/'05 Ford was installing the new design with better material so the problem wasn't as bad, but with 4 timing chains you will tend to have more timing chain issues that with an engine with 1 timing chain, lol.

The engine should be pulled out to do this work.