4020 Engine Knock

49 studie · Feb 17, 2022

We have a 1968 4020 diesel tractor that has a loud engine knock. It appears to be coming from the upper end of engine, and the knock seems to be in time with valve movement of the engine. We pulled the valve cover and everything looked normal. We set the valves but that didn't change the knock. The tractor builds 35psi of oil pressure and everything seems to be oiling fine on the top end of the engine. Any ideas on the source of the knock?

Dieseltech · Feb 17, 2022

Might be an injector stuck open, broken piston, failed wrist pin bushing. Did you try to find which cylinder by loosening the injector inlet nut so the leak takes fuel away from that cylinder? An injector stuck open will show as compression air blowing BACKWARD out the injector fuel inlet fitting. If the noise goes away with fuel away from a given cylinder and injector does not blow back fuel, the piston or wrist pin could still have damage.

susandiane · Feb 17, 2022

This is pretty old-school, but you might be able to isolate the cylinder with a mechanics stethoscope or the old reliable large screwdriver pressed against the block with the handle pressed just behind your ear. Good luck in what you're doing!

tim s · Feb 17, 2022

Strong chance it a scoffed or burnt piston..

J.Wondergem · Feb 17, 2022

(quoted from post at 19:53:47 02/17/22) Strong chance it a scoffed or burnt piston..

That would be my first guess. Also I use a three foot chunk of heater hose to find where different noises are.

ET · Feb 18, 2022

Spun rod bearing and the piston is hitting the head. Pull the oil pan and look for the blue rod cap.

bmiller36 · Feb 18, 2022

scoured cylinder, happened to mine water will start to come out of the weepholes in a short time. Bob

4020 Engine Knock

49 studie

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Dieseltech

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susandiane

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tim s

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J.Wondergem

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ET

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bmiller36

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