941 cat started knocking

so this morning i had a guy coming to haul my loader from one farm to another, i went and cranked it up before he got there to be letting it warm up. the temp was in the low 40s and i let the glow plugs warm up for around a minute and it still wouldnt crank up after a few more tries it still wouldnt crank. so i had to use some ether to get her to start and after it sat there for a while warming up, i got on it to load it and it started knocking, at first i thought it was a glow plug blowing out because i have had a few of the cheapos blow the centers out and would make a loud hissing sound from the air coming thru it. i went ahead and loaded it up and got it home and checked the glow plugs and they look to still be good. it seems like it takes about 15-30 seconds after cranking it up for the knocking to start. i took side panels off and stuck a hose to the engine everywhere i could with the other end to my ear and cant tell where it is coming from. only thing i see wrong when i took the side panels off is the oil filter has started to leak again and a fair amount at that, but i always check the oil before using it and it is still well above safe starting range on dipstick. any ideas where i should start my troublshooting?
 
I fhe guy use to much ether to start the motor maybe the crankshaft is crack or brooken I had a guy with 955k with same probleme at idle the motor was running fine but high speed he was knocking and the crankshaft was brooken
 
I can tell you where you are headed... You can remove the oil pan and check but engine is coming out and you will need crankshaft work. Welcome to the world of buying used equipment. At least you did get a year out of it before it broke. Labor will be the big cost , parts ever where for that machine.
 
Should be a 3304 engine in the 941,first off is the oil pressure still good,if not try not to run it any more till you establish what could be wrong,take off the oil filter and check it for metal flakes,if its showing metal flakes there is a good chance it has ran a bearing.if the oil pressure is ok it is possible the trouble could be an injector nozzle or a valve broke and the piston hitting it is the cause of the knock,loosen each injector pipe in turn to see if there is one that makes a difference,if you find one swap the nozzle to see if the knock follows it,if so change the nozzle.
AJ
 
Thanks AJ--I just recently bought a D6 9U with a knock and I will follow your procedure to find the problem.
 
(quoted from post at 06:37:25 12/11/15) Should be a 3304 engine in the 941,first off is the oil pressure still good,if not try not to run it any more till you establish what could be wrong,take off the oil filter and check it for metal flakes,if its showing metal flakes there is a good chance it has ran a bearing.if the oil pressure is ok it is possible the trouble could be an injector nozzle or a valve broke and the piston hitting it is the cause of the knock,loosen each injector pipe in turn to see if there is one that makes a difference,if you find one swap the nozzle to see if the knock follows it,if so change the nozzle.
AJ
i have loosened all the lines and couldnt tell no difference, it still has good oil pressure,i took the filter off and didnt see no metal in it, i saved the oil that was in the filter housing but havent strained it yet. and as far as engine i dont know how to postive id it but this is one of the early 941s 70h617 is serial so should be d330c
 
That's an early one,either way it is not the number of the engine that is causing the knock,it good that you have full oil pressure,check the filter for metal,check the coupling between the torque converter and the engine and see the engine mountings have not come adrift and the engine is loose,if that checks out take off the four fuel lines from the injector nozzles,squirt some fuel or oil into each nozzle and crank the engine over while watching the four nozzles,you are looking for one to blow back,if one is blowing back replace it,if they all hold take out the nozzles and and cobble up a compression tester and test the compression,if you find one low you could have a bent/broken valve,the head will have to come off.
AJ
 
Remove the fuel lines and then the four nuts that hold the nozzle in place,you can usually lift them out then if they are tight attach a fuel line and use a pry bar to prise them up.
AJ
 
had a local guy that works on heavy equipment for a living come and look at my loader and listen to it run for a second and he said he would about bet money its got a busted piston. what do yall think the chance of that is? he says its pretty common problem and hasnt had much trouble with the lower ends of these engines.
 
Its my guess that you have bent or broken valve that the piston is hitting,you need to have your mechanic take the head off to see what's wrong.
AJ
 
i took the head and oil pan off, from the top i can see one piston has a small chunk broke out of the side of it and has wore a small groove in the liner and looks like one piston was barely hitting a valve, but looked like there was a little chunk of built up metal or something on top of the piston that was hitting the valve.

i got the oil pan off but there is still the plate that is between the pan and block that has to come off, there is a "crossmember" in the way does the engine have to be jacked up a couple inches to get the plate off or what?
 
To get no 3 or 4 piston out that plate has to be removed,you will need to loosen the drive coupling to lift the engine up for to get clearance,the oil pump is timed as are the balance shafts,a chunk missing from the piston usually means a piston ring broke that is a common with using starting fluid,as long as the crankshaft is not damaged you can replace a piston or liner without having to pull the engine,it is still a lot of work but not as bad,when the engine is lowered again the alignment of the coupling has to be set so watch out for any shims under the mountings.
AJ
 
i took some pics of the pistons today, it looks like one piston has built up and was barely hitting one of the valves.

this is the first diesel i have ever rebuilt, have done several gas engines, but gonna attempt to rebuild this one myself.
have a couple questions before i start tearing it down any further and according to weather that will be next weekend.
1.is there anything besides the 4 bolts that holds the oil pump in
2.do i need to take the radiator out so i can take the front cover off so can be sure to set timing right?
3.will i need to take the rear skid plate off as well so i can get to the drive couplings? can get to the top half but dont think can reach the bottoms ones from the top.
4.if the crank checks out good im gonna put a inframe kit in it. anyplace yall recommend me getting one from? i got a price from one company for $1700, but another site i added all the parts going by my parts manual numbers for everything in a inframe kit piece by piece and total was around $600, not sure where there extra $1100 comes in.

thanks for everyones help so far im sure i will be asking more question later but maybe this will get me started
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Rad and front cover stay in place,you can loosen the coupling without removing the belly pan,oil pump has a pickup pipe connected to the plate,an in frame overhaul is the way I would go,you need to have the four connecting rods checked for alignment at the engine reconditioning shop,the cylinder head and valves needs checking too there is probably bent valves,that was rotten luck but at least if the crankshaft is ok it will save a major tear down,it is dishearting for that to happen after such a short time but with a new set of pistons and liners it will be as good as new.
AJ
 
i took the #1 piston out this morning which is the worst looking piston from the top anyway. rod bearings looks good, wrist pin is good and tight. what would have caused all the damage to the top of the piston? how do i go about checking and changing the main bearings? do i just loosen and change one at a time or some other way?
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Yes you change main one at a time,fab a tee that will fit in the oil hole in the crank,it must be a bit thinner than the bearing,put the tee in the hole and turn the crank by hand,that will push out the old shell and then the new one in,there was some foreign material in there going from cylinder to cylinder,check the glow plugs that there is not a bit missing,it could be a piston ring that broke up but whatever it made one hell of a mess.
AJ
 

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