engine seized by rusty piston

[bomdia]

i'm trying to free up one cylinder from a ford lehman 6cyl.
It is seized due to lack of use.
I've tried heat, boiling oil, more heat, penetrating oil. repeatedly.
I can see the barrier of rust around the piston that prevents the oil getting through,
Is there some chemical which will eat out the rust without eroding the aluminium piston?
Does anyone have any further advice, the engine is too low down in the boat to take off the sump and so expose the big end. Apart from getting a new engine.
Cheers

 

[SAMYL]

Have you tried turning the engine backwards? A common mistake is to turn the engine in the normal direction thus tightening it up further. Rock the crank back and forward gently with a socket/spanner on the pulley nut.

Sometimes a sharp crack with a block of wood and large hammer will break the seal in the bore but make sure the block of wood is about the same diameter as the piston otherwise you could punch a hole in it.

Lots of boiling water into the water jacket, but not on the piston, may expand the cylinder a little before you try the hammer.

You really do need a heavy hammer, like a sledge; hit it (the wood) firmly but not too hard, it should just need a good solid clunk.
Best of luck

 

[dmayes]

Mechanics tricks

If you can reach the flywheel try a tyre lever or long metals bar to lever the gear teeth first one way, then the other. This will give you a lot of leverage. Don't try for one direction, rock it back and forth to try to get penetrating oil into the rusty area. If you can get any movement at all then just work it back and forth and it will get better slowly. Once free, your rings will be jammed too so you will probably have to take the engine out in the end. Taking it out earlier will allow you to take of the sump, remove the bearings from the other pistons/conneting rods and just work on the one jammed piston. Many years ago I did just that with a land rover and ended up having to smash the piston out, fit a new one and I didn't even have to get it rebored, just sanded the rust away. That land rover ran perfectly for years after.

 

[lw395]

You have the head off?
I would try planing a bit of wood to almost fit the bore and contact the piston around the edge.
Then try to break the rust by hammering the piston down to bdc.
If that does not work, it's got to be engine out.
I have seen this work with bike engines that had lain around for years outdoors, but ideally you would want to get the piston out to clean out the ring grooves, de-rust the bore and remove any abrasive debris.

 

[30boat]

Make sure the piston is not on BDC or TDC before hammering.

 

[Boatman17]

i'm trying to free up one cylinder from a ford lehman 6cyl.
It is seized due to lack of use.
I've tried heat, boiling oil, more heat, penetrating oil. repeatedly.
I can see the barrier of rust around the piston that prevents the oil getting through,
Is there some chemical which will eat out the rust without eroding the aluminium piston?
Does anyone have any further advice, the engine is too low down in the boat to take off the sump and so expose the big end. Apart from getting a new engine.
Cheers

Hi there, bit of a long shot but if you are still on here, wondering how you got on with that seized piston.
I think I have the same on my ford sabre 280c.
Havent taken the head of yet, was hoping not to have to. Poured oil down the cylinders and leaving it soak.
Maybe someone else has advice.
Thanks

 

[rogerthebodger]

I had a similar wit a perkins 4/238.

I poured diesel oil into the cylinders through the injector holes and left it for a week.

Managed to to free with a 2 meter tube extension to a socket on the front crankshaft pulley

Hydrochloric acid will remove rust but may damage the aluminium.