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Old 14-01-2015, 02:42   #1
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Yanmar YSE12 cylinder head removal.

Any suggestions as to how to get the cylinder head off ?
I've removed the four nuts and the rockers and rocker shaft etc.
I've removed the injector.
I've removed the inlet pipe and the exhaust pipe.

The head just seems to be just stuck on tight. I've sprayed WD40-type penetrating oil around the studs, and I'll leave that a while, but I'm not hopeful that it'll achieve much.
A mate suggested sticking some rope down the injector hole and using the piston to ram the head off, but having taken off the injector, there doesn't seem to be direct access through that hole to the combustion chamber. And looking through the parts book I think there's some kind of pre-combustion chamber down there.

I have a 3ft wrecking bar and have been levering with that against the stub of the exhaust pipe, but with no effect. I could try a longer bar, like a 5ft crow bar, but I wouldn't be surprised in the exhaust stub broke first.

I've just about run out of ideas. The reason the head is coming off is because the valves are sticking and/or there's a blown head gasket. So there's no compression, so the idea of getting it running to compress the head loose is a non starter......

Any thoughts on the subject, or should I just resort to the longer crowbar ?



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Old 14-01-2015, 05:23   #2
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Re: Yanmar YSE12 cylinder head removal.

I like to use an old wood chisel and hammer. Insert the edge of the chisel between the head and the block flat side down, parallel to the block head interface at the point where the head bolt goes through, and tap lightly. The chamfer of the chisel will lift the head up with little or no damage to the head. If the studs are rusted into the head, it may be necessary to remove them first. Depending on the configuration and their condition, you may be able to use two nuts locked together on the stud to unscrew them, or a stud remover like this

to remove them, or it could even be necessary to weld a nut to them.

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Old 14-01-2015, 13:25   #3
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Re: Yanmar YSE12 cylinder head removal.

G'day, The rope trick will not work on a Yse 12 it is fitted with a pre combustion [Lombardo] cell. The clearance between the head studs and the head is large allowing corrosion to weld the head in place as you are finding out. I spent 10hrs removing one once using heaps of wd40 and Fox wedges[ Google].Give it good touch up in all directions with a sledge hammer crude but helps. Have you disconnected the oil feed pipe underneath the head? Patience and a sense of humour is the key.
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Old 16-01-2015, 11:40   #4
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Re: Yanmar YSE12 cylinder head removal.

Thanks Jim and Doug. The wood chisel and a 1.5kg lump hammer did the trick, followed by the judicious application of a 3ft crowbar ! I'm generally a bit more sympathetic to a poor dumb engine when I'm working on it, but in this case the cast iron head and cast iron block came off totally unscathed: not a scratch !

In the end, only one of the studs was seriously rusted up. The others were a bit oily- probably indicative of the leaking head gasket.

I'll clean it up tonight and pull the valves out. Hopefully a regrind will suffice, and maybe valve guides.

There was a slight lip around the top of the bore, but only slight. So I'm thinking just the valve job will do.

Thanks for your help.

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Old 16-01-2015, 12:21   #5
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Re: Yanmar YSE12 cylinder head removal.

Have the guides reamed or better yet, replaced. Not that hard and not that expensive
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