Valve drop :(

[chrisdefo26]

Coming home from work the other day and merging onto the parkway I got on it a little and immediately heard a pop then knock knock knock knock. Pulled over and had the truck towed home. Pulled the heads and found cylinder one dropped a valve and basically destroyed the piston and cylinder walls. Been running a ppe 90hp tune for the past 2 years. Truck has 178,000 miles on it. All maintenance has been done and injectors are probably less than 30k miles and injector rates were all good/ no hazing or raw fuel smell. First things first what could have caused it? Second does anyone have a block for sale lol 2004 lb7 with northeast emissions

 

[Fingers]

A lot of debris in the adjacent cylinder. Any other damage?

 

[chrisdefo26]

I’m assuming there is, I wasn’t able to immediately shut it down being on the parkway so it probably ran all through the motor. I’m pulling the motor from the truck this weekend.

 

[Chevy1925]

i think you have had this issue longer than you think. that adjacent cyl didnt get the same valve debris through it. im betting something happened to this engine back when you had your other "issues"

 

[chrisdefo26]

Could have been but the fuel issues were leaking injectors even after the new ones were installed then got replaced under warrant and the engine overheating ended up being just a bad ect sensor. Engine always ran pretty smooth other than that. At this point though I agree it could have been some underlying problem I didn’t know about.

 

[DAVe3283]

I agree with James, I think something else happened long ago. How long have you owned the truck?

As an example, I had two glow plug tips break off in my head, and I just ran it, hoping it would blow them out. One did, but the other went through the motor. Beat up the piston & head, and damaged a valve seat. Because I am that kind of person, I said "well, let's see how long it runs on 7.5 cylinders!" After a couple years and almost 10,000 miles, I tore it down to build the motor, and it was still running great aside from a weird exhaust note from the damaged valve seat. But really, a valve could've let go at any time and done what happened to your motor, I was just lucky (and saving up for a new motor, so not totally dumb).

Maybe something like that (piece of metal through the motor) happened to yours before you got it, and the previous owner was unscrupulous and just sold it as-is? Could explain the damage to the other cylinder. It is unlikely that chunks went back up the intake far enough to get to the next cylinder, IMO.

 

[mopar3]

It would make perfect sense to blow debris from the cylinder that dropped the valve back into the intake and get sucked up by the next cylinder. Seen engines that dropped valve a blow a bunch of trash up into the intake swap intake onto new a motor, and damage the new motor. When the intake valve is gone there's nothing to stop the piston from pushing junk up and out of the intake port.

 

[Burn Down]

Definitely could get material up in the intake and spread it to other holes. Happens all the time with engines that use a common intake or clam style.

I had an lb7 up in Alaska do the same thing.

 

[DAVe3283]

I would have figured that with a giant hole in the piston it wouldn't have much compression to move debris back up the intake, but anything is possible. Maybe it was just one event taking out both cylinders. I'm out of ideas as to what would've taken out that valve though.

Sent from my Cat S60 using Tapatalk

 

[chrisdefo26]

I’ve had the truck a little over 3 years. I never had the valves adjusted... any chance clearance could have became to tight and opened the valve a little more than it should have and got kissed by the piston? Or more like punched lol

 

[Tothemax]

valves would gain clearance with age.

 

[chrisdefo26]

Gotcha :thumb:

 

[Burn Down]

valves would gain clearance with age.

Actually they don’t, the valve seats and valve faces wear and the lash decreases.

 

[Tothemax]

Actually they don’t, the valve seats and valve faces wear and the lash decreases.

ive never seen a tighter valve clearance used engine only looser.

 

[Burn Down]

Cats 3500 series are notoriously hard on valve seats and faces. The lash tightens up over time always. If you have tons of hours I can promise the lash is tightening.

 

[chrisdefo26]

I was used to all my street bikes and dirt bike valves tightening but I guess that’s also from the high rpms and valve seats wearing pretty quick.

 

[jlawles2]

Actually they don’t, the valve seats and valve faces wear and the lash decreases.

As the valve and seat both wear, lash get tighter since the valve is actually moving up away from the piston. That makes sense on the close.

Since the top of the push rod is not moving and the lash adjuster on the rocker arm is not moving, the valve to piston clearance should stay the same. Correct?

 

[Fingers]

Look at the valve stem end. Bent, you ingested some debris at some time. I suspect that is what happened here.

 

[chrisdefo26]

Makes sense, it’s my first diesel so I guess I didn’t notice the signs. These motors are tanks lol it seemed to run pretty strong since I got other than when my injectors failed.