Tractor might be shot - now working on compression testing and have questions

[WinterDeere]

I wonder if the valve seats are hammered also causing no compression.

I'd be surprised. Think of the massive volume of that cylinder, versus the tiny surface area of any one valve seat. A damaged valve seat will cause leak-down, likely even reduced compression... but zero compression? I don't see how.

A valve stuck open might do it. But I'd be really surprised if a valve seat with sufficiently small damage to not see as soon as you pull the head, could do zero compression.

Of course, I reserve the right to be wrong. It's been known to happen.

 

[hayden]

A bent connecting rod could explain no/low compression, but I think I now understand that it was a push rod that was bent. But not totally clear.

 

[Racer4]

A broken valve seat that fell into the cylinder could do this too. It would also explain the no compression in that cylinder. I thought he had a bent con rod, but understand now it was a push rod. I’d try to remove the intake valve and inspect the seat to see if it’s even there.

 

[etpm]

A broken valve seat that fell into the cylinder could do this too. It would also explain the no compression in that cylinder. I thought he had a bent con rod, but understand now it was a push rod. I’d try to remove the intake valve and inspect the seat to see if it’s even there.

A broken piston would also result in no compression but since the piston top is not at the top of the cylinder that's probably not it. If the piston broke the top of the piston would tend to stay at the top of the cylinder. A bent push rod that doesn't move the valve might also be responsible for a zero compression reading because the valve might not open which would draw a vacuum when the piston descended and then when the piston returned to TDC the vacuum would be relieved. I'm really curious about what caused the damage and why the zero compression condition.
Eric

 

[Omnipotent]

Sorry, yes push rod bent, slightly but still bent. My guess on the zero compression, the valve is "chipped" around the base as shown in the first of the two pics, so I'm guessing lack of compression was caused by this, but I did examine the head gasket and it "appeared" in tact, ie no blow out, tear in the gasket (yes it's the metal crush gasket, just didn't know what else to call a rip in it other than a tear). I "believe" the valve could not seat properly due to the damage on the valve as described above.

Didn't tear into the bottom of it today as I got pulled away, hopefully during the week I can hop in the garage and start digging into it some more.

 

[Omnipotent]

Sorry guys, shade tree mechanic over here...just went back and re-looked at the head and in fact the #2 exhaust valve seat is missing, this explains the metal, damage and lack of compression.

Whew, at least I know where the metal came from, now the question of whether or not the head can be re-used or if a new on is in order (regardless of head outcome, a new piston and rings will be ordered at a min).

Thank for the help so far.

 

[hayden]

Sorry, yes push rod bent, slightly but still bent. My guess on the zero compression, the valve is "chipped" around the base as shown in the first of the two pics, so I'm guessing lack of compression was caused by this, but I did examine the head gasket and it "appeared" in tact, ie no blow out, tear in the gasket (yes it's the metal crush gasket, just didn't know what else to call a rip in it other than a tear). I "believe" the valve could not seat properly due to the damage on the valve as described above.

Didn't tear into the bottom of it today as I got pulled away, hopefully during the week I can hop in the garage and start digging into it some more.

Ok, thanks. It’s always good to have everything explained.

 

[etpm]

How in the heck can a person predict that? A broken valve seat that drops into the cylinder. I have never seen this happen in an engine. I'm glad you found the problem. Of course the way the piston is all beat up it will need to be replaced along with the rings. But I'm thinking that the head can be re-surfaced which will take care of most if not all of the damage. Any other slight damage that is left as long as any sharp edges are smoothed away, will probably have no significant effect on the engine. Since the piston and connecting rod are coming out I guess a new bearing for the connecting rod is in order. The head should of course be checked for cracks. I wonder why the seat fell out in the first place? Your head machinist will certainly be able to help out there. Good luck and thanks for all the updates.
Eric

 

[dodge man]

Diesels are such high compression, can you machine the head without losing some?

What hood the valve seats in? I had a Dodge 383 and the seats had been replaced with hardened one for unleaded gas. They were staked in.

 

[Racer4]

If you machine the head, compression goes up, not down. The machine shop will be able to tell you if the head is trash or not. Hopefully they can recondition it for you.