3C Crankshaft removal and re-grind

[CHRISEEBOY]

The engine in my 3C has siezed, big end on pot 4 to the crank.

Does anyone know how easy/difficult it is to remove the crankshaft from a 4/98 NT to have it skimmed? I would be grateful if someone could talk me through the process if they have done it themselves or seen it done?

[dixie-normous]

You will need to remove the engine, sump off, clutch and flywheel off and front cover too. The balance shaft below the crank has to be removed and if the bearing has spun in the big end you will need a new conrod too. You will need to fit a new oil pump, but check the oil filter element hasn't collapsed, i've seen this happen and it caused the engine to seize. The problem is, where do you stop? If the engine is out it is worth checking the bores and fitting new rings at the least but by this time it's starting to get expensive. If it was running ok before, you could just do the crank as the pistons can be removed from the top with the engine in place, but it's alot easier to while you have the engine out
John

[Jeremy Rowland]

As John says above; it really depends on exactly how bad the seizure was, and more importantly what caused the seizure, lack of lube oil, oil pump failure, oil-way blockage etc.
Having reground crankshafts in the past while working at a friends engineering company, you could additionally have a cracked crankshaft, my advice would be to drop the sump and see if you can remove the big end that has seized, then take it from there, too much damage then it would be easier to get another lump.
I would not even consider trying to remove the crank from the engine while it is in the machine, it may be virtually impossible to do it that way anyway so taking the engine out makes life easier. If the crank can be saved then remove the engine from the machine and strip out the crankshaft, take it to a reputable engine company who have a crank grinder, get a quote to have it ground, crack tested and a new set of oversize bearing shells for it, don't forget you will also need new seals and gaskets etc.
Let us know how you get on.

Jeremy

[MrF]

Having a crank ground and crack tested then new oversize shells is not a cheap proposition also.

And as already suggested imho its a engine out job to get to it. Even removing big end shells in situ past the balance assembly is difficult from personal experience.
By the time you've removed the sump guard, bellhousing half, clutch and flywheel, front pto shaft to the pump, front timing components etc, your not that far away from fishing the lump out complete to a place where it can be worked on properly and give it a proper inspection and any major work has a much greater chance of being successful as a result. If its a automatic you can't take the flywheel off the end of the crank in situ without removing the transmission somehow or the engine itself as you have to slide the motor/flexplate forwards to disengage it from the torque converter.

To extract the engine you'll need a gantry or engine crane with sufficient lift and capacity when its jibbed out and its a heavy lump at 500+ kg, so that's something to bear in mind. I got my engine out the first time by setting the crane up on the loader arms and it was sketchy as hell. In comparison with a forklift its quite easy.

[CHRISEEBOY]

Thank you all for your replies.

I have already dropped the sump and managed to get the lower bearing cap off the crankshaft and out of the machine. The upper bearing cap is harder to get to as the crank is in the way but I suppose im lucky that it siezed on cylider 4, not 2 or 3, as there is less stuff in the way.

As to the severity of the seizure I cant really comment as I havnt seen many seized engines in my time. It doesnt look like the bearing shell has spun, just welded its self to the cap. I think i can break the shell off but a new conrod my be in order. Is it possible to remove the top half of the bearing cap from the conrod or is it one solid piece?

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[dixie-normous]

Holy moly that did get hot! The top of the big end is part of the conrod, but looking at the colour of it i think i'd put a new one in. It will be a pain in the hoop to get the engine out but i think it's your next move, and will be less painful than trying to do it in place.I wouldn't bother taking anything else apart on the bottom end until you remove the engine, number 4 piston will have to come out completely to change the rod and i really wouldn't want to be lay underneath trying to get the crank out. The crank will need checking that it hasn't cracked as Jeremy and MrF say, but also that it hasn't bent. You can sometimes get away with having one journal reground but personally i would do them all and put a complete set of shells in. Check the balancer gear too, if the dowel bolts come out the balancer shaft will slide out and you will lose oil pressure.

[MrF]

Besides making that journal fit for work again and replacing the rod as Jeremy already said, you need to identify why its seized also. I would guess #4 journal is at the end of the lubrication circuit and the most likely culprit to suffer low oil pressure issues causing failure first so it could be the canary in the mine from issues elsewhere. I did some work for a turbo remanufacturer and while there they used to get quite a few returns on tested reman units failing on fitment, and they'd get the car to present at the workshop and on almost every occasion it would have feck all oil pressure to the turbo, instant warrantee refusal. I bet Jeremy has tales similar from crank grinding work...
I think dixie meant the top half of the conrod shell bearing is not part of the conrod, but I'm in agreement, its got so hot that you wouldnt want to risk reusing the conrod anyway.

For me a essential step would be checking all the oilways are clean and not blocked and that the pump and other components are in good order. It could be that all the shell bearings have worn beyond tolerance and are leaking pressure away so if you don't find the culprit you might just go through this cycle again in the near future when the new bearing suffers from the same fate. And I also suspect the head has to come off for that piston to come up out the top, I cant remember if when the crank out the piston has room to pass the webs downwards but I doubt it.

On the plus side, last time I seen a rod seize like this, we found remnants of it lying on the floor after it had snapped the crank in 3, and the conrod shattered and threw itself through the side of the engine block, and that really was beyond any recovery. And that happened driving it off the trailer at home having bought the tractor it was in that day.

[dixie-normous]

Sorry, yes i did mean conrod, i was very tired! As you say MrF, no 4 is at the end of the circuit so if the crank is very worn the whole engine could be needing an overhaul, rings, liners, valves and injectors. I think the problem with these older machines is justifying the cost, an engine rebuild can be well over half of the machines value. If the back acter has alot of play and things are generally getting worn, given scrap prices now it's sometimes more cost effective to weigh them in and buy another. Not saying this is the case here but i have seen it happen

[MrF]

It doesnt have to be machine-writing-off expensive though, well the crank itself wont be cheap if the journal is wrecked but the rest of it you could get away with just investing time. You won't know until you assess it and some parts are quite cheap, a conrod for eg I priced at 24 quid out of curosity. I have in the past lightly polished a journal with fine crocus cloth that had light smearing because when I picked off all the debris deposited from the bearing, it was only lightly scored underneath.

If you want to check bearing wear on the other pots and assess the other journals on the crank also, you dont need a lot of specialist measuring gear, you can use plastigauge if you dont know this already, this is a fairly informative write up on its use, and there's plastigauge kits under a tenner on ebay.
http://www.snowvalley.20m.com/bikes/plstgage.htm