Horrible knock after deaaceleration on freeway

[MN12valve]

hello all have a 1996 2500 12 valve Cummins with 305K. Today on way to work all was normal when I deaccelerated on the freeway and pushed in the clutch instant knocking noise from the top of the motor.

I was thinking injector failure. I was able to limp it about 3 miles to work it does feel like it’s missing and will even do it at stop lights at idle. Anyone with a similar situation. I have good oil pressure at all speeds as well.

 

[Missouri Mule]

PROBABLY NOT ENGINE PPROBLEM!
Your clutch fluid reservoir Is on the firewall on drivers side. The clutch cable is down and to the left. AS I recall is also a little further back. The hose from the resvoir goes to it. It mite not be cable operated,it could be hydraudlic. Have re-read read the clutch section again.

 

[MN12valve]

Well just an update to my original post. Cylinder number one has a bent intake push rod. Exhaust push rod top was destroyed. I also have a destroyed tappet. Thinking about doing a complete rebuild since truck has 306,000 miles on it. Anyone ever experience something like this out of the blue? truck was decelerating when it let go.

 

[B.G. Smith]

Thanks for the update. Yes, I would at least pull the head. Something bad going on in that #1 cylinder.

 

[GAmes]

I agree about pulling the head to see what is going on. 300k isn't normally enough to need a rebuild, unless you have been running a poor air filter or dumping waste motor oil or ATF into your fuel tank. Did the failure follow some other maintenance?