Random knocking rebuilt ford 8n

lanezupkov · Nov 24, 2016

I had my engine rebuilt recently and the tractor starts and runs beautifully EXCEPT this very random metallic knock or ping. I say random because it is not cyclical. It starts this sound after a few minutes of running.
I was so convinced it was a nut banging around in the oil pan that I dropped the pan but there was nothing in there, everything looked tight and I didn't see any signs of metal on metal scaring except the oil pickup tube was scratching on the oil pan. I also removed the guts for the governor since I thought it could be a ball hitting the case. no luck. When I do the long screwdriver to the ear trick the noise sounds the loudest in the oil pan, timing cover, exhaust manifold, and clutch housing (all sound chambers?).
I'm leaning towards pre-ignition knock but I've never heard engine knock in person also it i most noticeable at idle. I'm tempted to put in ear plugs and start mowing.

Den N Ms · Nov 24, 2016

Lane,Check the exhaust manifold for leaks around #4 port,it could be a exhaust leak making your noise.Look at the oil pickup for contact with a rod and bumping the pan.

ASEguy · Nov 25, 2016

Pre-ignition knock or detonation in my experience gets worse with load. More load = more(louder)knock. I think I would be contacting the rebuilder. Was the noise there before the rebuild?

S10Vette · Nov 25, 2016

(quoted from post at 20:58:31 11/24/16) I had my engine rebuilt recently and the tractor starts and runs beautifully EXCEPT this very random metallic knock or ping. I say random because it is not cyclical. It starts this sound after a few minutes of running.
I was so convinced it was a nut banging around in the oil pan that I dropped the pan but there was nothing in there, everything looked tight and I didn't see any signs of metal on metal scaring except the oil pickup tube was scratching on the oil pan. I also removed the guts for the governor since I thought it could be a ball hitting the case. no luck. When I do the long screwdriver to the ear trick the noise sounds the loudest in the oil pan, timing cover, exhaust manifold, and clutch housing (all sound chambers?).
I'm leaning towards pre-ignition knock but I've never heard engine knock in person also it i most noticeable at idle. I'm tempted to put in ear plugs and start mowing.

My bet would be the top of the oil tube where a rod nut comes very close. This is apparently very common, and mine had worn almost through. Would not be able to see it without a inspection mirror. Hate to say you need to pull off the oil pan again. If you carefully bend the tube make sure to support it securely at the main cap end so you don't stress the braze joint.

Dell (WA) · Nov 25, 2016

(quoted from post at 20:58:31 11/24/16) I had my engine rebuilt recently and the tractor starts and runs beautifully EXCEPT this very random metallic knock or ping. I say random because it is not cyclical. It starts this sound after a few minutes of running.
I was so convinced it was a nut banging around in the oil pan that I dropped the pan but there was nothing in there, everything looked tight and I didn't see any signs of metal on metal scaring except the oil pickup tube was scratching on the oil pan. I also removed the guts for the governor since I thought it could be a ball hitting the case. no luck. When I do the long screwdriver to the ear trick the noise sounds the loudest in the oil pan, timing cover, exhaust manifold, and clutch housing (all sound chambers?).
I'm leaning towards pre-ignition knock but I've never heard engine knock in person also it i most noticeable at idle. I'm tempted to put in ear plugs and start mowing.

lanezupkov · Nov 25, 2016

Not that i noticed and I agree pre-ignition knock would get worse with load, this is most noticeable at idle.

lanezupkov · Nov 25, 2016

oddly enough when I disassembled the engine I could tell there had been a repair where the pickup tube meets the housing so I examined that carefully when i pulled the pan off. Good clearance. Plus I think that sound would be cyclical.

lanezupkov · Nov 25, 2016

The sound is more metallic than blow by. When I removed the pan one of the things i was looking for was contact with the pickup tube since the previous rebuild seemed to have that very same problem (repair to pickup tube).

Dell (WA) · Nov 25, 2016

Lane..........3-posiblilities.........pre-ignition knock.......usually occurs under load.........HOW MUCH load is on yer engine at IDLE???........2nd posiblility.......BAD sparkplug seal.........recommend AutoLite 437's gapped 0.025. (4-sparkies $20, cheap)........3rd posibility.......loose starter bendix in clutch housing.......starter bendix's are known fer coming unlatched from end of starter shaft and bouncin' round in yer clutch housing. This would lend itself to random knockin' as it bounced around........HTH, the amazed Dell

Roger in Iowa · Nov 26, 2016

Did you have the crankcase drain plug with screen out when you reinstalled the pan? If not, you probably pushed the pickup
tube into contact with the crank rod throw.

lanezupkov · Nov 26, 2016

yes plug and screen were out when reinstalled pan.

lanezupkov · Nov 26, 2016

I really do appreciate all the suggestions I've received so far including starter loose bendix. It seems as though this tractor has been through all these problems before judging by the old battle scars including a discarded starter bendix in clutch housing. The noise definitely not there after initial start up and takes a few minutes to start. I didn't see and parts in clutch housing nor did I see any scaring on oil pickup tube when I had the pan off. I would not blame anyone form walking away from this especially since it's hard to diagnose a problem from one person description of a noise. I'm this far (//) from hauling it out to my property and mowing with it.

showcrop · Nov 27, 2016

(quoted from post at 20:21:29 11/25/16) Not that i noticed and I agree pre-ignition knock would get worse with load, this is most noticeable at idle.

The reason that Den N Ms suggested the manifold gasket is that this leak that he describes is known to sound metallic, and to be mistaken for the sound of metal striking metal inside the motor.

Random knocking rebuilt ford 8n

lanezupkov

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Den N Ms

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ASEguy

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S10Vette

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Dell (WA)

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lanezupkov

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lanezupkov

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lanezupkov

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Dell (WA)

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Roger in Iowa

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lanezupkov

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lanezupkov

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showcrop

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