Freeing a stuck engine
From Crankshaft Coalition Wiki
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==Preface== | ==Preface== | ||
Before you get out the sledge hammer and a block of wood and start pounding your meat there are a few things to consider. Most importantly: | Before you get out the sledge hammer and a block of wood and start pounding your meat there are a few things to consider. Most importantly: | ||
| + | *How long has it been since the engine was last turned over? | ||
*What condition was the engine left in when last turned over, is there oil in it still, or water? Or is it dry, without oil? | *What condition was the engine left in when last turned over, is there oil in it still, or water? Or is it dry, without oil? | ||
*Is the engine seized because of neglect/rust/corrosion, or is it because of a mechanical failure like a broken crankshaft, thrown rod, spun bearing or seized piston from detonation, etc.? | *Is the engine seized because of neglect/rust/corrosion, or is it because of a mechanical failure like a broken crankshaft, thrown rod, spun bearing or seized piston from detonation, etc.? | ||
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Below are three tools that can make turning the engine over a much safer operation than using the crank bolt. | Below are three tools that can make turning the engine over a much safer operation than using the crank bolt. | ||
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With the spark plugs out of the engine and a FULLY charged battery, give the starter a one second click and then stop. Observe as you do this if the fan or crank pulley has moved slightly, if the valves have moved, and if the starter is fully engaging into the flywheel. Take the breaker bar and turn the crank pulley back a bit and then hit the starter button again to put some torque on the flywheel. This torque multiplication will move the crank journal a degree or two and will push or pull on the piston which in turn will apply thrust against the rings. All you have to do for the moment is crack the rings loose a thousandth of an inch to allow the penetrating oil to get in between the rings and cylinder walls. | With the spark plugs out of the engine and a FULLY charged battery, give the starter a one second click and then stop. Observe as you do this if the fan or crank pulley has moved slightly, if the valves have moved, and if the starter is fully engaging into the flywheel. Take the breaker bar and turn the crank pulley back a bit and then hit the starter button again to put some torque on the flywheel. This torque multiplication will move the crank journal a degree or two and will push or pull on the piston which in turn will apply thrust against the rings. All you have to do for the moment is crack the rings loose a thousandth of an inch to allow the penetrating oil to get in between the rings and cylinder walls. | ||
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After allowing the penetrant to settle in for a few minutes to overnight, try to turn the crank in the reverse direction of rotation (CCW as you face the engine looking towards the distributor) to remove the tension on the rings. The penetrant between the ring and the wall will eventually break the ring free from the cylinder wall. It may take a dozen or so tries before all of the stuck rings and bearings are free but with each successive try more fluid will fill the voids until the engine is free to turn. Allow the engine to make two or three revolutions before stopping the exercise. This will allow the excess penetration oil to evacuate itself from the combustion chambers and for some of the oil in the crankcase to move in the system. The engine will now have a new place to rest while the lubrication seeps into the surfaces of the internals. | After allowing the penetrant to settle in for a few minutes to overnight, try to turn the crank in the reverse direction of rotation (CCW as you face the engine looking towards the distributor) to remove the tension on the rings. The penetrant between the ring and the wall will eventually break the ring free from the cylinder wall. It may take a dozen or so tries before all of the stuck rings and bearings are free but with each successive try more fluid will fill the voids until the engine is free to turn. Allow the engine to make two or three revolutions before stopping the exercise. This will allow the excess penetration oil to evacuate itself from the combustion chambers and for some of the oil in the crankcase to move in the system. The engine will now have a new place to rest while the lubrication seeps into the surfaces of the internals. | ||
| − | Many years ago the writer bought a | + | Many years ago the writer bought a van with a stuck engine. The poor aftermarket ignition wiring (the van originally had a diesel engine) had caused the engine to quit. The vehicle had been idle for over a year judging by its tax disc so Plus Gas was introduced into the plug holes daily for over a week. Trying to force the starting handle stripped the thread on the aluminum alloy jaw nut so that method of attack had failed. Fortunately the defective alloy part had been discontinued and replaced with a steel part so the new part was bought and fitted. Unfortunately even when the starting handle had timbers clamped on it for extra leverage the engine could still not be turned! At this point the starter motor was tried but the battery was too weak. A new heavy duty battery was purchased and this succeeded in freeing the engine on the third impact (the current draw was so high that the earth braid smoked!) The engine then fired-up and ran OK and at this point the astonished seller rushed out and said "Are you an electrician or something?" It was a great van and basically all it needed was two weeks of soaking with releasing fluid, a new battery and some attention to the ignition circuit. Engines from boats which have sunk are much more difficult. |
When pistons are stuck really hard, heat, the wood block and the sledgehammer may all fail. Also note that striking the crown of the piston is a very bad idea so ones oak block should be relieved in the middle. If possible obtain some thick-walled steel pipe and machine it to be a clearance fit in the bore. Pressure can now be applied to the edge of the piston where it is needed. If some all-thread can be obtained that will fit the stud holes in the block a hydraulic jack can be rigged-up but the key ingredient is TIME. For example the writer was privileged to be shown a seized vintage oil engine that was about a hundred years old. Its owner had been soaking the piston with red-diesel for a year however he said that he would not be doing any work on the engine until the piston had been soaked for another THREE YEARS but not many people have so much patience. In any case one also needs to consider the three-score-and-ten aspect when undertaking such lengthy tasks. | When pistons are stuck really hard, heat, the wood block and the sledgehammer may all fail. Also note that striking the crown of the piston is a very bad idea so ones oak block should be relieved in the middle. If possible obtain some thick-walled steel pipe and machine it to be a clearance fit in the bore. Pressure can now be applied to the edge of the piston where it is needed. If some all-thread can be obtained that will fit the stud holes in the block a hydraulic jack can be rigged-up but the key ingredient is TIME. For example the writer was privileged to be shown a seized vintage oil engine that was about a hundred years old. Its owner had been soaking the piston with red-diesel for a year however he said that he would not be doing any work on the engine until the piston had been soaked for another THREE YEARS but not many people have so much patience. In any case one also needs to consider the three-score-and-ten aspect when undertaking such lengthy tasks. | ||
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