mashed / squished push rods

[clinter36]

Hello,

I purchased a non-running skid with a Shibaura N844LT engine (2L 4 cyl). Also a Cat 3024c and Perkins something.

As I am just getting into the engine, it appears all of the push rods are mashed at the ends. The tips look to be blue ish from overheating also (see pic)



I am curious if anyone can tell me the possible cause of this... ? ether? or possibly filling the oil too fast and hydro-locking (owners manual warns of filling the oil too fast as it will flow into the intake)

I guess I should pull the head and have it rebuilt while replacing the push rods. Does anyone think the damage could have extended into the bottom end of the motor or do you think I am OK with heads? Obviously I will have to inspect the pistons more when I pull the heads.. I would like to avoid pulling the entire engine if I can do just the top end work.

Thanks for the input.

 

[ruffdog]

Hydro-locking normally bends connecting rods. When you pull the head, check your piston to deck height on all cylinders for bent rods. Push rod damage mostly happens when the valves contact the pistons. If all the push rods are damaged, I would look at the timing gears between the crankshaft and camshaft.

 

[kenmbz]

Timing chain or belt break or if direct gears, missing tooth or gears not meshing?
That would cause such a massive overlap easily

 

[pmsmechanic]

To me it looks like the push rods are blue from the welding process during manufacturing. It's common for industrial push rods to have a bell on one end and a ball on the other. Take it to a dealer or an overhaul shop and a mechanic should be able to tell you what is normal for that series of engine.

 

[clinter36]

Yeah, you may be correct. I looked at a couple pics of new ones and they do appear to be blue on the ends. But certainly this cap has fallen off and the rod is clearly deformed a little at the ends. The machine has 4k hours. Just debating on pulling the engine out and just doing a full overhaul or do push rod / head work and call it good. I guess I will know more when the head comes off.

 

[dodge man]

I would think if the damage was from valves hitting pistons not all the push rods would be damaged, just a couple. Is this the kind of engine you adjust the valve clearance on. Would the valve lash be totally out of whack cause this? A problems with the rockers?

 

[TractorGuy]

Just bought a VW sand rail with the same issue. Not likely it was a hydro locking problem on an air cooled engine.

The ones in mine were aluminum and I replaced them with chrome moly.

 

[ericm979]

You can hydro lock an air cooled engine. Hydro locking just means getting too much of a liquid (i.e. water or fuel) in the combustion chamber that the piston can't fully compress. For example driving it into a stream above the air intake. (which may also hydro lock the driver if the air intake is up high, but you get the idea)

It's not that uncommon for push rod caps to come loose. If it's been loose for a while it'll damage the softer metal of the tube. The blue looks factory.

 

[Gem99ultra]

I would expect some cam damage as well. Safe thing to do is to pull the engine and go completely through it. No telling what else you'll find that needs repair. Better to catch it all on one pass than to keep running into problems later.

 

[Tinhack]

Yeah, those ends are typically "spin welded" to the shaft. I've seen them come apart on engines with excessive valve lash or a really worn cam. That would have been a noisy engine!

 

[clinter36]

** Update **

So I pulled the engine and tore it down. I thought everyone might be interested in what I found...

both pushrods from #1 cylinder were bent - the one in the pic from the first post and the other was clearly bend mid shaft. And sure enough, after pulling the head, you can see where the valve kissed the piston (pic)



I figured we would find play in the connecting rod bearings, but after pulling the crankshaft and checking / measuring everything, the crank is in really nice shape. I took the head and crank to an auto machine shop. They are going to polish the crank and rebuild the head. BUT, he looked at the head and basically told me the whole story. He said he could tell the head gasket was leaking - if you don't see a really clean ring around the cylinder, its been leaking. And when it leaks, it usually goes to the coolant passages and pushes the coolant out and the motor overheats. When the motor overheated, the valve could have stuck just a bit and smacked the piston.

What I find interesting... and I guess it makes sense. If the valve hits the piston, it is slammed back so hard that it hits the rod and can bend the rod, basically in mid air.

Anyway, that is where we are at. The pistons were pretty scored however the cylinder walls look pretty good. I was sort of hoping to get away with just honing the cylinders, but I have to measure them and see how round they are. Apparently that is one of the first things to go on these little diesels when the motor overheats... the cylinders warp.

 

[TractorGuy]

Better check the timing gears or chain whichever it has. Valves don't usually make contact unless something has gotten out of time.

 

[clinter36]

Timing gears are perfect... backlash within spec, no visible wear or chips.

 

[pmsmechanic]

Was the engine over revved at some point?

 

[TractorGuy]

I wonder if the head was resurfaced? I would take extra care and checking on the assembly.

 

[fried1765]

I wonder if the head was resurfaced? I would take extra care and checking on the assembly.

That little N844LT is a sweet running engine.
I have it in my (Shibaura) Ford 1920.

 

[TractorGuy]

** Update **

So I pulled the engine and tore it down. I thought everyone might be interested in what I found...

both pushrods from #1 cylinder were bent - the one in the pic from the first post and the other was clearly bend mid shaft. And sure enough, after pulling the head, you can see where the valve kissed the piston (pic)

View attachment 686179

I figured we would find play in the connecting rod bearings, but after pulling the crankshaft and checking / measuring everything, the crank is in really nice shape. I took the head and crank to an auto machine shop. They are going to polish the crank and rebuild the head. BUT, he looked at the head and basically told me the whole story. He said he could tell the head gasket was leaking - if you don't see a really clean ring around the cylinder, its been leaking. And when it leaks, it usually goes to the coolant passages and pushes the coolant out and the motor overheats. When the motor overheated, the valve could have stuck just a bit and smacked the piston.

What I find interesting... and I guess it makes sense. If the valve hits the piston, it is slammed back so hard that it hits the rod and can bend the rod, basically in mid air.

Anyway, that is where we are at. The pistons were pretty scored however the cylinder walls look pretty good. I was sort of hoping to get away with just honing the cylinders, but I have to measure them and see how round they are. Apparently that is one of the first things to go on these little diesels when the motor overheats... the cylinders warp.

Are these pistons installed correctly? Any idea if the engine was apart before you got it? It looks like the valve made contact forward of the relief that was cast in for valve clearance.

 

[CoyPatton]

Are these pistons installed correctly? Any idea if the engine was apart before you got it? It looks like the valve made contact forward of the relief that was cast in for valve clearance.

From looking at the picture, the valve contact appears to be within the piston valve relief area if the piston had been installed 180* from what we see in the photo.
That seems to indicate someone has been there before or improperly installed from the get-go.

 

[clinter36]

Sorry, I forgot to watch this thread as I moved over to the continuation of this with the cylinder measurements. I attached piston installation pages from two manuals. It appears to me they are the correct orientation based on the sketch. I did not notice an arrow.

View attachment piston assembly.pdf

View attachment piston assembly 2.pdf

 

[TractorGuy]

Sorry, I forgot to watch this thread as I moved over to the continuation of this with the cylinder measurements. I attached piston installation pages from two manuals. It appears to me they are the correct orientation based on the sketch. I did not notice an arrow.

View attachment 686766

View attachment 686767

Hard to believe they would cast in valve reliefs then position the valves in the cylinder head to align with the flat top of the piston. Maybe those depressions in the pistons have more to do with the combustion chamber?