Hey guys....I've got a 98 F150 with a 4.6 that is making a god awful clacking diesel type sound. I've taken it to two different mechanics and both of them have said that to them it sounds like collasped lifters but neither were for sure without tearing it down.....It sounds much louder on the passenger side than the driver, but it's so loud it's hard to pinpoint. If you was standing by the motor you would think it had a mild diesel engine in it.

The diesel sound, sounds exactly the same at cold start up and after the engine has been ran all day, etc. It doesn't get worse or quieter except when you UP the rpms, obviously. They put a tester on it and it read bank two lean.

any ideas

 

well I guess it is the lifters....sounds just like this, but maybe a little louder but the overall sound is exactly the same.

YouTube - 04 f150 with bad lash adjusters (lifters) on passenger side

 

The first thing to do is put a mechanical oil pressure gage on it to see if you have decent oil pressure. You might also check the oil pan for debris from the timing chain guides coming apart and clogging the pick-up screen. It's not uncommon.