Kohler CH18s with rusted tight pistons

sorner · #1 05-23-2017, 07:56 PM

So I have this Kohler CH18s I'm parting out, got it for free. It was full of rain water, so I'm pretty sure the block and pistons are toast. They are severely rusted. I've been soaking with various fluids and heating the bore with a torch hoping to cause some movement. I can't get them to budge yet. The problem is the crank is at the top of the stroke and the pistons are near the top also. So banging one piston with a block of wood is pushing on the other one. So I'm working against myself in a sense. Does anyone have any good ideas to break those loose? The crank looks like it's in good shape. I got the connecting rod caps off and there is very little if any wear inside. I think this is a very low hour engine, it's disappointing someone left it get this way.

ol'George · #2 05-23-2017, 09:32 PM

Well if it were mine, I'd drive on the piston with an oaken block and have a helper try turning the flywheel @ the same time with a pinch bar in the teeth, or @ least hold tension on it trying to turn in the right direction.
do clean up the bore with a deglazing hone somewhat, because when one piston it going down the other is usually coming up depending on the crank throws.
Also use plenty of penetrating oil.
once it moves ever so little, reverse direction working it back/forth.

olds45512 · #3 05-23-2017, 09:35 PM

break the piston with a chisel, they're junk already.

john hall · #4 05-23-2017, 10:07 PM

On engines that are stuck pretty good, you need to remove one piston at a time. If you have the bearing caps off, can't you turn it in the opposite direction so you are only dealing with one piston at a time? I've never heated an alum. block and pistons, but have done cast iron. If they are junk, try what Tim suggested--break them using obvious precautions. FWIW if you are trying to save them, you need a block turned with a slight clearance on the bore, and with a relieved center. That way when you hit it, all the force goes to the outside (skirt) and doesn't risk breaking the piston. Sometimes time is needed--days or even months to let penetrating oil do its job.

I'm assuming you have taken the valves out of play--I folded up a couple pushrods failing to do so on my crawler.

The grey Case we managed to clear the tractor off the ground trying to jack the last piston out of it.

J-Mech · #5 05-23-2017, 11:10 PM

Quote:

Originally Posted by olds45512

break the piston with a chisel, they're junk already.

Quote:

Originally Posted by sorner

So I have this Kohler CH18s I'm parting out, got it for free. It was full of rain water, so I'm pretty sure the block and pistons are toast.

Oh... you have no idea. You can salvage the block. As long as you don't ruin it doing what your doing.

Quote:

Originally Posted by sorner

They are severely rusted. I've been soaking with various fluids and heating the bore with a torch hoping to cause some movement.

STOP THAT!!!! DO NOT heat it with a torch! Your going to tear something up. The block is likely salvagable. Just bust the pistons out like Tim suggested. DON'T damage the cylinder doing it though. A big gouge and it's over.

Quote:

Originally Posted by sorner

The crank looks like it's in good shape. I got the connecting rod caps off and there is very little if any wear inside.

It will need ground. I'm going to say you have no idea how many hours are on it by looking. I mean really..... how many crank shafts have you pulled out and "looked" at. Maybe 4 or 5? 3? Not saying it's bad, I'm saying you have no idea.

sorner · #6 05-24-2017, 05:55 AM

I've seen several and higher use engines have at least some wear in the bearing cap. These look like they just came out of the box. You're right though, I have no idea. That's just a guess. It's not a tree I can cut open and count the rings. At this point if I can just save the crank I'd be happy. Is cutting the rods an option so I can get the crank out and then drive the pistons one at a time to try to salvage the block? The valve lifters and cam shaft are out already. I think I have room to get in there with something to cut the rods off to free the crank.

Mike McKown · #7 05-24-2017, 06:40 AM

I've torn down several V-8 engines that were stuck due to rust/corrosion in the cylinders. I turned the block upside down and drove the pistons out the top of the bore with a steel driver rod and many licks from a two pound hammer.

After I got several of the rods/pistons out, I could rotate the crank out of the block.

I need a few small parts from a CH Kohler if you're parting the rest out.

sorner · #8 05-24-2017, 08:33 AM

There's no way I can get anything in there to bang them out from the bottom with the crankshaft in the way. I'll keep soaking them with penetrant for a while and see what comes of it. One side is worse than the other on top of the piston, and underneath the pistons the bore feels pretty smooth yet, and not rusted. I wish the crank pin was positioned to the right or left, then I think banging the pistons from the top would knock them loose a little easier. Right now with it stuck at the top position, banging on the pistons is basically forcing the piston and rod directly into the crank pin and stopping any motion right there.

J-Mech · #9 05-24-2017, 10:35 AM

Just break the pistons from the top with a chisel there ace....

sorner · #10 05-24-2017, 10:30 PM

Well, I got in there and carefully buzzed off the rods and got the crank out. The crank looks perfect. I guess I'm only losing out on the block and pistons and rods at this point. I'll try banging the pistons out tomorrow and if that doesn't get them out, the chisel will. There's nothing in the way now but rust and corrosion with the crank out of the way. I want to try to be careful to possibly save the block, but if it goes badly, the block is a loss right now anyway, so I don't stand much to lose at this point.