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SmilinSam

7790 Diesel Questions

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CarlH
I have not been into my diesel any further than a valve job so take my input as opinion only. The service manual diagram of the lubrication system (not real clear) seems to show the last items on the pressurized oil supply path are the valve train (pushrods and rocker arms) and the camshaft (crank/rods gets the first shot at oil), so those would would be the first things to look at in an oil starved engine. Rod/crank knock would be more pronounced under load (or higher RPM). A guess would be camshaft/lifter or rocker arm/pushrod. My fixer-upper diesel at first was only firing on one cylnder (LOTS of smoke!) but still had enough power to easily move the tractor up loading ramps and to mow with. The problem was a burnt valve and valve retainer disintegrating. Good luck, Carl

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SmilinSam
Ok, 1) It starts and runs easily, and runs smoothly 2) It idles at low RPM good 3) the motor mounts and bushings are all now in good order 4) the driveshaft is diconnected for the meantime 5) It still has the sharp "clink" sound(like something slapping into aluminum. 6) at low RPM the sound is intermittent but never completely goes away 7) It usually does not do it right away from a cold start, it takes a half minute or more to start in doing it 8) It does it with much more frequency and more uniform as throttle increases but still does not seem rythmatic. 9) sounds like it is coming from the upper end of the engine to the front of the engine(best guess) Since it runs it is obviously fixable or rebuildable. I have no shops around here that work on these, so I'm on my own. Anyone have any ideas based on the above? Knocking rod? Carbon build up on the heads? Rocker arms out of adjustment? I really don't have any idea as compared to other problems in my gas engines. I doubt I will go to the expense of a rebuild, would sell either the engine seperate or with the tractor. But I would like to investigate a little more to see if it is a lesser problem before I go that route. Looking for a direction to go. Thanks, Sam

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Sandy_Lake_Imp
We have repaired many sheared governor hubs on these engines. The original rivets shear off. We replace them with screws. Loose rivets could be the cause of your noise but the gov is on the rear of the engine. I have also found a blown head gasket to cause the noise u describe. Bill

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