Freeing a stuck engine
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?
- 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.?
 Taking a look at the engine
Start by removing the air cleaner. While removing the air cleaner, check for moisture or water puddles in the oil bath or in the bottom of the filter housing. It might be dry now, but look for evidence of there having been standing water in the past. The reason that you are looking for moisture is to determine how much water could be within the engine. If snow is blown into the engine compartment, it will melt and puddle out inside the air cleaner, intake manifold, lifter valley, etc, but not necessarily make its way deep into the engine. If the engine has been flooded by means of overland flooding and rising water, then you could also have an accumulation of silt and dirt within the engine. Dirt and water within the engine is the worst kind of engine lock that you can experience.
Pull the dipstick and check for water in the engine oil. If you find water in the oil, try to determine how much there is. Start by removing the oil drain plug from the oil pan and watch what comes out. Water will exit first, followed by whatever oil that may be left. If the engine was flooded excessively, there will be basically no oil left; it will have been pushed out by the rising water. The ratio of water to oil that comes out of the oil pan is an indication of whether the reciprocating assembly was submerged or not.
Open the radiator cap and check for coolant. If no coolant is present in the upper tank, open the drain tap and check for the presence of antifreeze. You can remove an upper radiator hose housing and check under the thermostat, too. In some cases, you can open an engine block tap or remove a water jacket stud to look for coolant, too.
 Understanding water damage
If the water is from an external source such as rain, and it came into the air cleaner via the butterfly stud on the air cleaner, chances are there is only a small quantity in only a few of the engine bores. You can only have so many intake valves open at one time, and the water would have only migrated into those cylinder bores. Therefore, you could only have two or three stuck pistons at the worst, not all of them. In such a case, the likelihood of freeing the engine is much better. On the other hand, if the engine had been flooded by rising flood waters, water could have entered via the exhaust system. To make matters worse, water may have also entered through the oil breather and is now (or was) present in the oil pan. Flood waters also have a large presence of silt, chemicals of unknown nature, and varying pH.
 Flood water damage
The silt particles present in flood water could accumulate deep inside of the engine and hang on to the rough casting surfaces of all the internal workings. These particles are so small that when they are in solution they will infiltrate the oil clearance of a bearing. When the water dries, they will form a layer of dust within the bearing. The dust will wick up the oil from the surface and water vapor from the air will start to rust the steel surface over time. The dust may also have acids and alkalies (caustics) attached to it, and together with water vapor will etch the bearing and journal surfaces.
After a flood, newer, essential and operational vehicles take priority for being repaired, others will have to wait. Many flooded engines will just have to wait, sometimes until after the winter freeze-up, sometimes even longer. Internal damage and cracked blocks and heads are often the result of frozen water. Sometimes they will end up being junked for the cast iron. If these engines are gotten to before such damage occurs, it may be possible to salvage them intact.
What you discovered above will lead you to understanding the solution to unsticking the engine. An engine that was in a covered shed, had no visible sign of water infiltration, and was full of oil and coolant- but stuck- is usually an easy fix. The rings, which are cast iron, are usually stuck to the cast iron cylinder walls but only in the cylinders which are open to the atmosphere. If you followed the firing order of the engine, you could determine which are open cylinders and which are closed. You can start by pulling the spark plugs out and inject penetrating oil with a trigger type oil can.
Diesel fuel reeks and will leave a foul smell on everything it comes in contact with. For that reason, diesel fuel is not recommended for use unless that is all that's available. Marvel Mystery Oil, PB Blaster, or even kerosene/ATF mixed together are all acceptable. WD 40 or kerosene may work but are not as effective as some of the others fluids mentioned. DO NOT use gasoline or other highly flammable solvents as they do not provide any lubricity, plus they are a respiratory and fire hazard.
Note: Some years ago, a machinist's magazine did a controlled (but unscientific) study on penetrating oils, and found that ATF mixed 50/50 with acetone outperformed all other penetrating oils by a wide margin. Be aware that caution should be used when mixing or applying acetone-containing mixtures. Acetone is highly flammable, especially so when suspended in air and should be handled with care. Acetone is also an inhalation hazard. Should you choose to use ATF and acetone, be aware that the two components don't actually mix. They do work together as a suspension though. Therefore you want to agitate/shake/stir the heck out of it before each use for best effect.
Use plenty of penetrant in each spark plug hole and allow to sit for a few hours. While that's working, (if the engine is in a vehicle) back off on the fan belts, remove the air cleaner and valve covers. Charge up the battery, clean the cables and make sure all electrical connections are tight. Remove the fan shroud if there is one. Get a long breaker bar with the appropriate socket for the front pulley bolt. Remove the coil wire from the distributor/coil. Get some help if you think you need it.
 Breaking the engine loose
Note: Using a breaker bar to turn a frozen engine over by the crankshaft bolt is not recommended. The acceptable method involves turning the engine from the flexplate/flywheel, or by using a crankshaft socket that fits over the snout of the crank or bolts to the damper. Exceeding the torque rating of the crank bolt can - and will - snap it off, costing a lot of time and trouble to fix.
Below are three tools that can make turning the engine over a much safer operation than using the crank bolt.
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.
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 Commer 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.
Plumbers suppliers sell pipe-freezing kits (BP of the Freon replacement -50C) so it is fairly easy to freeze a piston to try to un-stick it from its bore. Liquid Nitrogen is better (BP-196C) but its not so easy to obtain. Dry ice or even a carbon dioxide fire extinguisher are also very effective in creating sub zero temperatures (BP -57C). Propane which is easy to obtain boils at -42 degrees C but there is the fire hazard to consider.
Just used all methods above and freed up Mercruiser 200 that sat for 2 years with oil drain pug removed and water filling up the oil pan. Mix 1 part MMO, 1 part WD-40 Specialist, 1 part PB Blaster and 1 part ATF -the cheap stuff works just fine as you will be draining. Remove spark plugs and spray Sea Foam Deep Creep [ one can on each side of block ] into cylinders and let sit for 1-2 days. With Proforms Engine rotation adapter p/n 66782 or similar remove the pulleys and install adapter to front of harmonic balancer, attempt to turn crank in small increments. Fill cylinders again and reinsert plugs. Wait 1-2 days and repeat, this time, fill the engine with the 5 gal mix posted above. Continue to turn crank in small increments. Mine moved about 1/8". Continue the cylinder spray alternating PB blaster and Sea Foam Deep creep. After 2 weeks, top of engine with 4 quarts of 15-40 hd oil. Continue to turn crank. Mine let go tonight after 2 weeks of this treatment, great feeling. Be sure to tap crank as mentioned in this article with longitudinal force, this seemed to be what caused it to "let go". Note - use the 1" socket on the Engine rotation adapter or you will break the tool from force on the internal 1/2" drive cut out while trying to break the engine free. Good luck and the hardest part, HAVE PATIENCE
 After the engine has broken loose
Now that you have broken the engine loose, one of the first things to do is change the oil. This will get rid of most of the dirt, acids, and penetrating fluid. Pull the drain plug, remove the filter and let it drain. Refill with clean motor oil and install a new filter.
 Engine flushing
Note: There is quite a bit of controversy regarding using various methods to flush/clean an engine that's been neglected. One school of thought is that it's better to leave it be, if the engine cannot be taken apart for a thorough cleaning. An engine that's had regular routine oil and filter changes will be relatively clean inside. Using a flush to clean it out won't accomplish much except to loosen what there is in there already. Once the crud is softened up, it can take a long time to ever be removed totally. It can take several oil changes to bring the engine back to a state where the oil and filter isn't immediately contaminated with the loosened dirt. Beyond that, there may be no damage done.
The decision to flush the engine will be left up to the person paying the bills. It is strongly recommended to research this fully before undertaking the procedure.
The following is one of many methods for flushing an engine:
- Add a gallon or so of diesel fuel and a new filter, and turn it over with the starter for a minute or so. You'll be turning it over without spark plugs, so watch for spray coming out of the plug holes. It will turn much faster and build up some oil pressure while cleaning out the oil galleys and internals. You can cycle through a few times if you want.
- Use a commercial engine flush, following the directions.
- Fill (fully or half and half, etc.) with ATF and run the engine.
 After the engine is freed up
You now have to make a choice: run the engine as is, or pull the heads and pan to check for damages. If you're going to do a compression test or a leakdown test, drain and refill with new oil. Circulate the new oil throughout the oil galleries by cranking the engine to purge the diesel fuel, and then start the engine to warm it up and burn off some of the diesel fuel in the engine. In most cases you should go the overhaul route, checking for wear, mic'ing out the bores and clearances of bearings, etc.
If the engine is all together you may have success by running hot water through the engine. This takes HOT water, 180 degree or so. Remove the thermostat and attach your hoses to your heating unit and pump the hot water thru the cooling system. Most frozen engines are caused by rings being stuck to cylinder walls. The theory here is the heat will expands the cast iron block faster than the pistons; the extra clearance this creates gives the penetrating oil a better chance at reaching the stuck areas as well as may break any bonds formed by rust/corrosion. One way is to use a homemade oil burner water heater system with a pump. If possible use the starter to budge it as you pump the hot water.
 Unsticking the "impossible"
The basics of unsticking any engine are the same. Fill it up with a fluid that will penetrate and lubricate the stuck surfaces. Remove or loosen any accessories that may be frozen up and causing the engine to be harder to turn over. Usually just loosening the belts will help with this.
Start by turning the crank, even a small amount will - over time and with repetition - cause it to break loose. Or it will tell you that the engine is well and truly frozen up and needs to be disassembled for a proper rebuild. Even a degree of movement or a thousandths of an inch is a start in moving the engine's reciprocating assembly. Allow time for the penetrant to work and don't get impatient.
 Using penetrating fluids
Using a fluid that will penetrate and lubricate is key. You need something that will penetrate, stay wet, and wick its way up into the smallest area. Ordinary motor oil will coat but penetrates at a very slow pace. Petroleum or mineral spirits will get into small places but will dry out over time. Paraffin will wick its way up or down a threaded bolt, but only when it is melted. Acids will eat their way through but can cause damage of its own and may be hard to control as well as dangerous to handle. Caustics are more of a slow burn and may require heat to work better, and are often harmful to aluminum/aluminum alloys. Water will penetrate, wet, and coat but has many limitations. Diesel fuel is a middle-of-the-road fluid that will creep, coat and stay wet over time but reeks to high hell and will stink up everything it contacts- you included. If you're feeling adventurous, you can mix up your own solution (WD-40 did). Or just spend a few bucks on a large can of Marvel Mystery oil, WD-40, or PB Blaster.
Know what metal that you are working with and apply the correct solution to get the best result. Most metals will form what is known as an oxide, where oxygen from the air mixes on the surface with the base metal. We do know that when these oxides dry out they are usually hard to remove by any means other than mechanical (sanding or wire brush/wheel, sand/bead blasting).
We know that steel or iron will rust. Aluminum will form a white powdery residue (aluminum oxide, or aluminum 'rust) and may form a dark grey to almost black coating caused by the oxidation of the metal. Brass and copper will be covered with a green corrosion. Each condition will require a different approach in most cases.
Heat is an excellent tool for unsticking things, but only when used in moderation. Would hitting a stuck piston help it to move? The answer is, yes and no. If you apply enough force in the proper direction, yes it would help. If you just wound up and smacked it dead center with a ball peen hammer, you would probably just put a hole in it and it would still remain stuck. The better way to approach this when you have a stuck engine would be this way:
- Determine what is stuck. Is it the piston(s), the crank, the cam and valve train, the rods, or a combination of all these?
- Break the engine down until you find that part or combination of parts.
- It would be a hell of a waste if we just gave up on an engine just because it wouldn't turn over. How about turning it back? Could we have just dropped a valve on the piston and it's stuck there?
- Remove non-essential accessories that aren't required to make the engine rotate. That means that you can loosen the belts or remove the alternator, water pump, intake and exhaust manifolds, distributor, heads, oil pan, etc. Get it down to where you can have a good look around and see where the problem area lies.
- Keep the engine in a secure holding device. If it's the frame of the car or truck, that's good. If the engine is loose, find a way to hold it down. Remember, the tensile strength of steel is greater than wood. And if one bolt is good, a half a dozen would be better. If using an engine stand, use caution that it doesn't tip. A light-duty three wheeled engine stand won't do it if a long breaker bar is going to be used to turn the crank.
- Flood the engine block with the fluid of your choice. Turn it upside down and fill the block, and plug holes as necessary. This is just a pre-lube stage.
- Using an oak block and a dead blow hammer of your choice, SHOCK each piston with a few blows. An air chisel with a flat bit and an oak block like the mushroom end of an axe handle works well. Remember you are just trying to loosen the rings, NOT move the piston. Just let the bit vibrate the oak block and piston. When the rings break free you will see your lube run past them into the block. Any piston which is at TDC or BDC will not give you any mechanical advantage in rotating the assembly by hitting it. The initial strike is to just loosen the rings in the piston lands and break the rings free from the walls of the cylinder. Pistons that are in between TDC and BDC will provide the best opportunity to move within the bore.
- There are two places in which you can apply rotational force; the crank pulley and the flywheel. Use whichever is accessible with the least effort. Do not use pulleys or the outside ring of balancers to turn over the engine if at all possible. Don't use the balancer bolt, either. Damper/balancers can be damaged and the damper bolt will strip if excessive torque is applied. Instead, the safest/easiest way to turn the crank is to use a tool that allows a large ratchet or breaker bar to be used, like the crank turning devices shown below. Both sockets that use the crank key, and adapters that bolt to the inner hub of the damper are made for turning the crank. Crank keys and keyways can shear with abnormal force. Be sure of the bolt grades before applying force. Remember to try to rock the crank CW and CCW.
- Don't forget to use longitudinal force on the crankshaft. Tap the crankshaft at both ends with your dead blow hammer and oak block, like you were going to measure the crank end float. Loosen the rod bearing caps and tap with a bronze hammer to break the bearings loose.
- After you've done all of the above, let it soak and then start over again.
After trying the aforementioned soaking to no avail, determine which cylinder is on the compression stroke by removing the spark plugs and using a compression gauge hose or other hose that fits snugly in the spark plug hole. Blow in the hose, if you can't easily then you have the one on compression stroke (if you use a compression tester hose make sure it has no Schrader valve in it). Break the porcelain out of an old spark plug and thread the metal body for a large grease fitting (1/4" NPT). Insert the plug in the cylinder that's on the compression stroke and pump it full of grease using a grease gun filled with cheap light weight grease (like Lubriplate white grease). Once the motor breaks free you can rotate the motor to squeeze most of the grease out of the spark plug hole.
Another approach is to put some Marvel Mystery Oil, WD-40 or PB Blaster into each cylinder and then pressurize with compressed air. On cylinders that are not under compression, the compressed air will distribute the penetrating oil. With the cylinder under compression, the compressed air will act to rotate the engine while driving the penetrating oil past the rings.
There are tales of Coke being used to loosen a stuck engine. Presumably this has something to do with the small acid content of Coke. Try it if you want to.
Warning: Use good eye protection. Blow compressed air into all the cylinders to coat the cylinders and piston tops with the penetrant. Give it a couple minutes/hours/days so it can work on the rust. Afterwards, screw in the compressed air adapter and charge each cylinder with fifty or so psi. It helps if you completely loosen the rockers first so any cylinder you charge has the valves closed. If it doesn't turn over at fifty psi it's not ready. Apply more oil and wait. It's time consuming and may be a bit of work, but the object is to SAVE the engine.
 Unsticking an engine in a manual transmission vehicle
Success can be attained in unsticking an engine in vehicles equipped with a manual transmission on a number of occasions by using the pre-soaking methods mentioned above.
Once the engine has soaked, jack up one drive wheel, put the transmission in high gear and work the wheel back and forth.
If you have a friend to help you can skip jacking up the wheel, put the vehicle in low gear, position yourselves on each end of the vehicle and rock the vehicle back and forth. This can take quite a while and it is quite tiring but you will notice the wheel will start to move a little farther if the process is going to succeed.
Once the drive wheel rotates several revolutions, pull the vehicle in high gear several miles with all the plugs removed. This is probably not necessary but it gets everything well lubricated.
I have used in the past brake fluid and ATF mixture. I generally coat the cylinders each day and try to turn engine. Generally after a few days I can usually free up a stuck or seized engine. This is the method we use in the Junk yard. We have access to free lubricants.