Once an engine reaches 160000 miles it has earned the right to have a knocking sound. If it has had proper care, it may be a bit pre mature to develop an engine knock, but we don’t know the purpose of this vehicle. If it is a commercial vehicle it may simply need a replacement engine.

I can’t see or hear the engine from here, and no, don’t bring it closer to the phone. My suspicion is that you have a tired engine. If an experienced mechanic gives it a good eyeballing and does not see anything obvious, than some diagnosis is in order.

You might want to hook up a master oil pressure gauge and see what the oil pressure is cold as apposed to hot, when the noise goes away. Finding low oil pressure probably means your engine is tired. It may mean the oil pump is going bad or the bearings in the engine are getting loose. Since the noise goes away hot, it may simply be the lifters are not ‘pumping up’ until the engine warms up.

Get yourself a good diagnosis. Regardless of why the noise is there cold and not hot is an indication in this case that there is probably an engine wear issue. At this point you have to evaluate what the problem is, how much it costs to fix and it the fix is cost effective for an engine with 160,000 miles on it or should you go ahead and install a rebuilt engine and solve the problem. Fixing an old engine may be spending bad money in this case.

The most reliable solution in this case seems to be a rebuilt Ford engine. At 160,000 miles we know the current engine has plenty of other wear issues. even if you can fix the engine for a reasonable price, you are most certainly looking at other wear and failure issues soon. Fix it for good and fix it fast, purchase a certified, pre tested rebuilt engine from GotEngines.com and cure your problem for at least another 160,000 miles.