Seized engine.

[Dom U]

Alright guys here's my dilemma, I acquired another jeep that has a "seized engine".It was giving him running issues so he parked it. He drove it about 7 miles from his sons house to his house ,parked it and it sat there till i bought it. we tried to jump it when i went to pick it up he was sure it would start since he drove it there and parked it. I'm told the jeeps never over heated has 201k miles on it and i trust the owner i got it from and iv known the jeep for years myself. I got the jeep home and immediately removed all the plugs and attempted to hand crank the engine with a 3/8 ratchet only i was actually able to to turn it about a 1/4 turn and stuck. Pulled out the 1/2 breaker bar and still nothing. Filled all the spark plug holes up with MMO and gave it another shot the next morning. Still nothing so i tried to go counter clock wise and it turned with ease a complete 360 and stopped again untill the bolt started to come loose. i can go back and for worth with it about a full turn of the crankshaft pulley but thats it. I'm stumped as to what it could be. I have another engine to swap in but i love bringing things back from the dead and could use some opinions  on this one. TTIA

[Jeep Driver]

Dropped a valve. 

[Eagle]

21 hours ago, Jeep Driver said:

Dropped a valve. 

 

Gotta be something like that. Time to pull the head and look inside.

 

If you can get 3/4 of a turn, it's not seized. There's mechanical interference and you just have to keep digging until you find out where it is.

[Green Mesa XJ]

My first though was something is dropped off inside the motor.
If you have the tool or phone accessory you could scope it to see what happening inside the cylinder.
I’d probably just pull the head to see what’s going on. I’d be surprised if it were something like scaling on the cylinder wall, dropped valve and/or screwed up position would by my guess.

BTW Guys I used to work with would soak a locked up engine with ATF over night to free it up. May be redneck but it worked a number of times.


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[omega_rugal]

I think you should always take the head off before attempting to turn a "seized" engine... specially if you have no clue about why it won`t turn...

[gogmorgo]

X2 on the dropped valve, or something else interfering with the piston travel. I had a bike engine rebuild do that, spin 360° In either direction and then stop very solidly, turned out one of the high-compression pistons had a manufacturing error and was contacting the head. Took us a bit to find it too because once we had everything back apart everything was turning freely, and everything was where it was supposed to be.