JCB 3C wheels not turning well, please help!

[JChrisB]

Yes, anti-freeze in the coolant, and also a bit of emulsified oil on the rad cap...

Im not going to lie, this digger is in a bad way. Oil in the water, probably water in the oil, oil and water both require topping up after every use, sounds like the clutch has gone, developed a flat front tyre over night, the list goes on!

If it is the head gasket, what would cause it to blow? If I replace it, what's to say it won't blow again as soon as i fire her up?

[gecko.cx]

Yes, anti-freeze in the coolant

Excellent - probably only a head gasket then.

If it is the head gasket, what would cause it to blow?

Head gaskets have a rough life: temperature cycling, high pressure pulse every time the cylinder fires, water / coolant on one surface, oil on another and combustion gasses on a third. The head and block expand at slightly different rates as they heat up causing sheer across the gasket and then you'd like to think the head bolts were torque'd evenly. It's surprising head gaskets don't let go more often.
Over heating the engine does it's own damage. This can be caused by low coolant, blocked radiator (either inside (water galleries) or outside (air fins)), running a lean mixture (not common with diesels as it's an excess air cycle) and a failed (or failing) thermostat are all common reasons for overheating.
Another less mentioned cause is the water pump. As the clearance between the impeller and housing increases, the performance drops off.

[JChrisB]

This digger came with my property when i bought it in 2020. I don't know how long it had been sitting in the field but it was in a sorry state. The engine was seized and it had no roof.

I took the head off and poured transmission fluid in each pot, hoping it was just a stuck cylinder. To cut a long story short, it wasnt. It was a slipped bearing on a big end. The point is, I already replaced one head gasket about 4 years ago. I tightened the head bolts in the correct order and down to the correct torque, then re-torqued them all after a bit of light work. Ive probably only done about 50hrs work since then. Surely thats too soon for a new headgasket to fail unless there is something seriously wrong?

Im just wondering if its time to call the scrap man? If I replaced to headgasket again it probably wouldn't last long and I would still have the clutch and flat tyre to resolve.

Has anyone got any experience disposing of a 7.5ton paperweight?

[gecko.cx]

That's not a happy story. A spun bearing is most often the result of over reving or lack of lubrication (low oil, oil so old it no longer provides protection).

Did you find anything wrong to cause the 1st failed gasket?
If the thermostat didn't open six years ago and hasn't been replaced since ... etc.

If it "had" overheated, the head and or block may be warped, so just fitting a new gasket couldn't be expected to last.

These are just guesses and suggestions, nothing concrete.

[JChrisB]

As far as im aware, the headgasket didnt fail but it was necessary to replace it after removing the head. Its impossible to know the cause of the the spun bearing, i didnt get the opportunity to talk with the previous owner, but im guessing oil deprevation. The sump contained about one litre of really bad oil.

I think i should probably start a new thread about how to sell/dispose of a non-running JCB. I just dont know where to start, its not as if a potential buyer could turn up in a 4x4 and tow it away!

[Billy26F5]

I would't give up that quickly. It sounds to me like you needed to retorque it again. JCB specified when assembling, then when hot the first time and then after 50 hours work. I recommend doing it more, it's quite amazing how far the bolts go further. See what happens after retorquing. Bare in mind that unless you have tool 18G 396 the rocker shaft has to be removed to do this. Also, make sure you reset tappet clearances after doing this. If it doesn't improve it might be damaged liners. Are you sure you didn't run out of fuel? That doesn't answer the water explosion but it does explain the splutter and stop. Another important thing is to ensure the block and head are clean and flat, but not totally smooth with composition gaskets or they can fail, some light machining scores help keep it in place. Do check the thermostat, the wrong thermostat will cause overheating. If your funds are limited just take your time, you don't need to finish it in one go. We took 16 years to rebuild Super Billy's engine, and he's doing fine now. There are small issues but not related to the delays. An oil change never does harm either, and spun bearings require big cleaning to avoid repitition. Always change the filter when changing the oil.
Sandy

[JChrisB]

Thank you for the moral support Sandy.

I was waiting for someone to mention liners as this was also my theroy. As I have been loosing oil (and water) after every use, with no discernible leak, I figured the liners must be failing and letting oil past which then gets burnt up in the pot. Has it now reached the point where the liners as so bad that compression has been lost?

I have watched videos on how to replace cylinder liners, and to be honest, I dont think I have the necessary equipment/facilities to pull that off. Am I right in thinking the crank shaft has to be taken out? It looks like a very lengthy proceedure envolving all kinds of specialist tools that are built for one specific use.

In terms of the headgasket, I remember having to remove the rocker shaft and remember how fiddly it was to get it back on. I did everything by the book and torqued and retorqued the bolts (in the correct order) after getting the engine hot. I wont have reached the 50hr mark so havnt retorqued again yet.

[Billy26F5]

I suspect the liners might have pin holes and or cracks. Bore wear can't cause the pressure to build up in the cooling system, it'll cause the breather to be very oily and possibly smoky, as well as blue smoke in the exhaust. Liners can be removed without removing the crankshaft but not a great idea. A sort of liner puller will be desirable but might not be necessary, especially if correct coolant has always been used (although then liner trouble is rare, it normally comes from rust). No other special tools are actually necessary, a ring expander and compressor are worth having though. Depending on the state of the valves you might want to check them too while you're there, but if they look ok the can wait. You might want to try asking friends, you never know if they might have such tools and might be able to help too. JCB say to remove the engine, but if the crankshaft doesn't come off you should be able to do this with the engine in place, although it will be awkward.
Sandy

[essexpete]

Might it be worth seeing if you can find a complete running engine?

[mechman]

Hi Chris.
What's the latest on the the JCB? Interested.
Norm.