JCB 3CII Engine seized- rebuild

[Jeremy Rowland]

Hi,
I managed to undo the crankshaft nut with the 1" Drive socket and bar, plus a 8' scaffold pole, had to bolt down engine to workshop floor to stop it turning over.
It appears only the number 2 rod journal is damage from loss of oil, the rest look ok, can you just regrind one or do they all have to be done?

David

David its common practice to regrind all of the crankpins; the main bearing journals may get away with a polish but they may also require a regrind, if an engine fails on only one crankpin then the causes could be; that the engine was run with a low oil level, that debris from worn bearings blocked the oil feed to the crankpin or that particular crankpin big end was badly worn.

Jeremy

[Mrsmackpaul]

You wont know what needs to be done until the person grinding it measures the crank even surfaces that appear fine my not measure round any more
If to much was ground of one part of the crank it would then be out of balance whether this would be enough to cause a problem I dont know
If it was mine I would get them checked and ground all the same size if needed

Paul

[Dave-OLW]

I am taking to grinding engineers for them to check it.
The O ring came out on the tube from the oil pump to block.
Will let you know the result
Thanks
David

[Jeremy Rowland]

David make sure that your oil pump pickup strainer is clear and free from any obstruction before you re-assemble the lump.

Jeremy

[Dave-OLW]

Not Good news, they say the crank is bent and is therefore scrap. As soon as he saw it he said it was bent, and put it on a machine and put a dial gauge on the centre main bearing, the gauge was going up and down, does this proof it is bent, could not the bearing be oval? Will have to look for replacement Crank or scrap the whole machine.

Thanks
David

[Dave-OLW]

Trying to confirm engine number, on the Main machine label it gives it as 6797, but cannot find this on the engine block. The only details are as shown in photo:-



I assumed the engine number is on the small plate which is riveted to block, but this appears to say 29 K 3 which does appear to be engine number.

Do I accept the number on main traction unit is correct?

Thanks David.

[topkit]

What area are you in David, i have a 3C 4-98 block complete with head that came out of a machine that had a fire that i would sell.

[Jeremy Rowland]

Not Good news, they say the crank is bent and is therefore scrap. As soon as he saw it he said it was bent, and put it on a machine and put a dial gauge on the centre main bearing, the gauge was going up and down, does this proof it is bent, could not the bearing be oval? Will have to look for replacement Crank or scrap the whole machine.

Thanks
David

David the crank must be bent greater than 0.030" or you would be able to save it by grinding; cranks can bend under the force of a seizure; Topkits engine may be a good proposition because if the crank has bent then there is a high chance that the block would require the caps "dropping" and being line bored through.

Jeremy

[Mrsmackpaul]

yes your going to need to look into this further before you go any further it costs nothing to look
I would think if it was mine would take the block in next and check it as well
Did you see how far the crank was bent ??? as Jeremy says maybe you could grind it back into shape if it has gone to far that you could build the crank up and then grind it back to original size
I have never had this happen so I dont really know but if the crank was bent as bad as your led to believe wouldnt the crank have still been hard to turn over when it was in the block when the bearings were still on ??

Paul

[Dave-OLW]

What area are you in David, i have a 3C 4-98 block complete with head that came out of a machine that had a fire that i would sell.

I am in the Midlands - Stafford.
Is it a NT ie has Balancer, was it running ok.

David