My 98 F150 V6, with only 63K miles on it, would not start one day. made a loud clacking noise under the right windshield wiper (near the battery). AAA came and said the battery was nearly dead and replaced battery. still wouldn't start, so towed to mechanic (a good all-around shop but not a Ford or truck guy), who thought it must be the starter and replaced it. Truck didn't start, so he pulled the starter and tried to handcrank engine without any luck. He pulled the plugs to look for signs of water (none). We were about to replace the truck but are now stuck with what appears to be a dead engine.

any thoughts would be appreciated.

 

Hey Tom, Welcome to FTE. Glad you found us and hate to hear about your situation.

When the mechanic tried to hand crank the engine, with the plugs out, could he? Was he able to turn the crankshaft by hand?

I tell you, it sounds like the motor hydrolocked, something broke, and now the motor will not turn over.

Have you drained the oil to check for any water/coolant contamination?
Have you checked the coolant level in the tank to see if it is low?

If the motor simply will NOT turn over (starter or by hand) with no spark plugs installed, then I see no other option beside starting to tear into it to see what is wrong.
Maybe remove the oil pan and see what you see.

I'm guessing it is related to a failed lower intake manifold gasket and subsequent liquid in a cylinder that caused damage when the starter was engaged.

Keep us posted!