EEVEE

So what would cause these engines to spin freely in a 180-270 (do NOT quote me as this is a friend relaying info and wasnt keeping exact track of it) degree rotation pattern and just stop back and forth each way? Im thinking a valvetrain issue, maybe jumped timing but arent these a non interference engine? its so locked the starter wont even turn it over. Friend says no glitter in the oil as well but he is further diagnosing as i initially thought maybe it was fried bearings or a spun one. 4.0 naturally lol. I guess it was driving down the road for him before it screeched at him then "locked up" the belt is off and every accessory drive spins. supposedly the hard spot was so tight it unloosened the crank bolt so he decided to spin it on the flywheel teeth and came to that conclusion when he spun it backwards and it was free moving till it stopped the other way. I want to be there to help take a gander for myself but he is in another state lol. No knocking or funny things happened beforehand so i dont think a wrist pin or something is loose. But i dont know i cant gauge things online without touching it im just wondering what more i could relay to him to look for. told him to also look to see if its anywhere near tdc to see if it jumped timing lol.

Kuro89

Lost a wrist pin? Won't know until you start pulling it apart.

doublechaz

If for some reason I was unwilling to open it to see the thrown rod/broken piston I would pull all the spark plugs and with an assistant put a long wooden dowel down each hole while the other turned the engine slowly and see that a piston isn't going up and down.

Slightly more logical would be to pull off the valve cover and see the valves all moving or not.

A friend of mine threw a rod by not knowing that the pinging was impoartant and driving up a mountain grade anyway. His oil was fine. He didn't hear anything mechanical. And yet there was the 3 inch hole in the side of the block that he searched for and didn't find.

EEVEE

Lol yeah like i said just wish i was there to take a gander at it myself. He did borescope it and inside the cylinders it looked all fine and dandy. If he finds anything more ill update but for now its a bit puzzling not seeing it myself. He is pulling the oil pan sometime this week to gauge a better look inside. also valve cover isnt a bad idea either i dont know why i didnt think to say that lol.

EEVEE

oh... thats why. yeah he pulled 5 of em before and the last one he waited on to get more space to do it and yeah lol.

lawsoncl

Time to pull the pan and have a look at the damage. That wrist pin isn't lost, but I'd wager it ain't attached to the rod anymore and the piston is seized in place.

EEVEE

Allegedly he stuck a camera down the spark plug hole and there is only the top of the connecting rod seen. soo all in all not very good at all.