4.0 manual knocking only when how

[thameren]

My 98 4.0 with 245k km has started knocking only when fully heated up at idle doesn’t happen every time and and once the revs go above idle it stops and it will randomly stop it definitely seems to be in the oil pan I’m running 10w30 Lucas high zinc wince it’s a very old design motor and it always makes good oil pressure 35psi idle when hot and 50psi driving at 2k rpm

 

[macleanflood]

What's your question?

-Mac

 

[DuckNut]

Cracked piston skirt

 

[thameren]

What's your question?

-Mac

Trying to figure out what the noise would be

 

[macleanflood]

Well everything we can do is a wild ass guess born from some experience.

For a definitive answer you need to tear the motor down. Oil pan, pull the head...pull the pistons off the crank.

You might be able to guess more scientifically with more data... compression and leak down tests...oil analysis from Blackstone.

DeXJs has some excellent videos of quick and dirty 4.0 refreshes.

-Mac

 

[Gilaguy23]

I'll take door # 3 bob for Lucas garbage.

 

[thameren]

Well everything we can do is a wild ass guess born from some experience.

For a definitive answer you need to tear the motor down. Oil pan, pull the head...pull the pistons off the crank.

You might be able to guess more scientifically with more data... compression and leak down tests...oil analysis from Blackstone.

DeXJs has some excellent videos of quick and dirty 4.0 refreshes.

-Mac

Pulled the oil pan today and everything looks good no cracked pistons and con rod bearings look good pulled the oil filter part with a cutter and there was lots of material and compression was good on first 3 last 3 where 110 80 and 70… guess it’s time for a rebuild

 

[macleanflood]

You might get away with bearings, pistons and rings if the cylinders aren't scored.

-Mac