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8n front engine knock

C

canald

New User
I was doing some road work, after a few hours, the engine developed a knock around #1 cylinder. I would have bet it was a rod knock. 20 year old engine rebuild with around 500 hours on rebuild. Parked the tractor, dropped the pan and pulled the head. No metal in the pan, no marks on the head or pistons. Rod and main caps are tight. Have not checked rod and main bearings yet. Rotate engine by hand, rotates smoothly. Water pump, front pully, timing gears all tight. No place in crank or cam. There is some discoloration in the red paint front left corner of head and block, like it got hot, but temp gauge was normal. I have read about sleeves coming loose but when I was turning the engine by hand, sleeves don't move. But that could be because the engine is cold, could move when hot.
I'm out of ideas.
 
Canald,Did you first check for a exhaust manifold leak? A manifold leak can sound just about like a connecting rod or wrist-pin knock.Look for signs around all four exhaust ports,such as black carbon,or burnt paint from bad gasket or eroded manifold/block.
 


2X exhaust manifold leak. I haven't experienced it myself but it has come up here a few times. The 8Ns block tends to rust behind the manifold, so that the gasket will of course deteriorate.
 
(quoted from post at 06:02:13 02/12/21)

2X exhaust manifold leak. I haven't experienced it myself but it has come up here a few times. The 8Ns block tends to rust behind the manifold, so that the gasket will of course deteriorate.
Click to expand...

Thanks for the ideas. Keep them coming.

No problem with the manifold or gaskets. The old manifold had a crack in it so i replaced it a few years ago.

The oil pressure was 40 even after the knock started.

Still puzzled on how to see if my sleeves are moving when running.
Maybe I need to pull the pistons and pull on the sleeves.
 
(quoted from post at 09:24:58 02/12/21)
(quoted from post at 06:02:13 02/12/21)

2X exhaust manifold leak. I haven't experienced it myself but it has come up here a few times. The 8Ns block tends to rust behind the manifold, so that the gasket will of course deteriorate.
Click to expand...

Thanks for the ideas. Keep them coming.

No problem with the manifold or gaskets. The old manifold had a crack in it so i replaced it a few years ago.

The oil pressure was 40 even after the knock started.
I would look mor marks on the head for signs of sleeve hitting the head


Still puzzled on how to see if my sleeves are moving when running.
Maybe I need to pull the pistons and pull on the sleeves.
Click to expand...
 
Canald,You say,No problem with the manifold or gaskets. The old manifold had a crack in it so i replaced it a few years ago.Two years ago doesn't mean that the gasket/block is not bad now,be sure!Then pull the pistons and check the wrist pin bushings for looseness then check the sleeves for being loose in the bores,Mark your piston order 1 - 4 and front side.
 
(quoted from post at 09:03:01 02/12/21) Canald,You say,No problem with the manifold or gaskets. The old manifold had a crack in it so i replaced it a few years ago.Two years ago doesn't mean that the gasket/block is not bad now,be sure!Then pull the pistons and check the wrist pin bushings for looseness then check the sleeves for being loose in the bores,Mark your piston order 1 - 4 and front side.
Click to expand...

Yes for sure on the manifold. No rust, no black makes or carbon on head or manfold. Gaskets were pristine.

I was afraid of that. Once I pull the pistons, if the sleeve is the problem, should I be able to pull it up by hand?
 
Canald,Should I be able to pull it up by hand?Yes if it that loose it is knocking.Be sure it hasn't dropped a sieve,but then you would see it in the pan
 
3x on checking the exhaust manifold. I blew the gasket in mine (suspect a prior owner never totally tightened the nuts as it came off waaaaay too easily) around the top corners of
#1 and #4 and it sounded very, very much like a knock. Well, before it started huffing and blowing exhaust at my leg when the gasket blew the rest of the way through, that is...
 
Don't know how common it is but it has happened to me. The sleeve rides up and down with the piston and makes quote a knock. When i pulled the head i could see the sleeve. I could push it back down by hand.
Hope this isn't your issue or else you will have to drop your pan and remove piston to fix. I JB welded mine back and it's been good for 20 yrs. but there is probably a better cure.
 
My '50 developed a distinct knock within my first couple years of ownership. When I started taking it apart, I found that the front crank pulley bolt had backed out enough for it to make a knocking noise. At that point, I made the decision to go "in for a dime, in for a dollar," and took it all the way down for a full rebuild. Still running great 13+ years later.

2018_plowingdone.jpeg


es
 
Ok folks, I removed the pistons and rods.

I tried to move the sleeves, still solid. Sleeves look and feel very smooth. I have not measured them yet.

The rod bears are nice and grey no copper showing, a little light scoring but nothing on the crank rod journals.
I may still replace the rod bearings. Piston wrist pins have no play. C clips still intact.

Pistons 1, 2, and 3 look good a little light scratching on the sides. The scratches are not deep enough to feel them.

Piston 4 looks the same as above pistons except the top of the piston. I see little indentations in the top of the piston and
corresponding indentations on the head. These are about the size of a pin head, there are a few of them.
I remember a few years back, I replaced the spark plugs. I did see some bird seed around the plugs. (We have mice that collect the
bird seed, from bird feeders, and eat them on the tractor motor). I used air to blow the out but maybe a few fell into the combustion
chamber. I think I can clean up the rough edges on the piston and head. I don't think this was the knock since it was more prevalent
near #1 cylinder.

Thoughts?
Dan
 
(quoted from post at 16:58:04 02/13/21) Ok folks, I removed the pistons and rods.

I tried to move the sleeves, still solid. Sleeves look and feel very smooth. I have not measured them yet.

The rod bears are nice and grey no copper showing, a little light scoring but nothing on the crank rod journals.
I may still replace the rod bearings. Piston wrist pins have no play. C clips still intact.

Pistons 1, 2, and 3 look good a little light scratching on the sides. The scratches are not deep enough to feel them.

Piston 4 looks the same as above pistons except the top of the piston. I see little indentations in the top of the piston and
corresponding indentations on the head. These are about the size of a pin head, there are a few of them.
I remember a few years back, I replaced the spark plugs. I did see some bird seed around the plugs. (We have mice that collect the
bird seed, from bird feeders, and eat them on the tractor motor). I used air to blow the out but maybe a few fell into the combustion
chamber. I think I can clean up the rough edges on the piston and head. I don't think this was the knock since it was more prevalent
near #1 cylinder.

Thoughts?
Dan
Click to expand...


My thought i still the same as it was along with four other responders before.
 
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