Ive been wrenching on stuff for most of my life but never come up against this. Bought a 2002 explorer 200,000 miles clean everything worked got about 700 miles bad noise started was told timing chain problem started research here ,youtube bought haynes manual, took off valve cover passengr side guides gone , pulled motor borrowed special tools replaced all cassettes gears chains guides cleaned all plastic out of motor put back in ran perfect for about 20 miles then motor shutdown had to get towed home found front timing chain broke and bent a valve pulled back down with motor in car machine shop fixed head new front timing chain & cassette from ford put back in ran perfect for about 20 miles broke down again towed again now other cam not turnig does anyone have a clue ho or why brand new timing chains could break this must take a heckuva lota force. I havent took passenger vaalve cover off yet i just know the cam is not turning.

 

Cam timing off, piston hits valve, cam stops, chain breaks...

.... Philip

 

This makes sense but if the cam timing was off wouldnt this happen at initial startup not 20 miles later?

 

Something mismatched or not assembled correctly. Perhaps an oiling problem. Bearing issue with the cams. You have to take everything apart to find the smoking gun.

Serving suggestion:

Buy a working later model 4.0, even one out of a Mustang. Transfer your accessory, intake, exhaust if needed etc over to it.

One member here described this as a "hateful" engine after doing one time what you are about to do three times.....

 

thanks i think thats where im headed its just a shame the motor ran so good then go to s--t so quick plus all the new parts.

 

My wife bought a new 2002 4.0 SOHC Explorer. It developed that dreaded timing chain cassette common expensive problem at under 34,000 miles. Dealer told us that's a "normal sound". At about 37,000 miles the dealer said "to bad so sad", out of warranty and it's going to cost a bloody fortune to fix. I had a UOA done and the iron in the oil was sky high do to the loose chain slap. She traded it into another Ford dealer for a new 2005 Explorer with the 4.6 V8. She still has it with 165,000 miles and it runs great. Ironically she only lost 1mpg by going to the 4.6 V8.

Whimsey