The gentle way to loosen stuck pistons!

[boschmike]

Take a spark plug and remove the ceramic part and electrode.
Solder a grease nipple to the spark plug base.
Skrew the device into the cylinder head, then use a grease gun to slowly release the piston.
Take your time and let the grease have time to its job!
Good luck Mike

[cuyler1]

i always filled cylinders with kerosene, let set overnight or longer then take a breaker-bar and deep well socket to the crankshaft pulley bolt an d rock it back and forth. i don't force it just apply a little pressure one way then back the other. if it moves any at all i stop and add motoroil to the cylinders , let set overnight again. this may be a slow process as all the cylinders must make a clean pass. i usually turn over by wrench until my shoulders' are about to fall off. just to make sure nothing is broken inside. then with the plugs out i crank the engine over to get most of the kero-oil mix out . replace plugs and fire up.

[DcnBlues]

I have always used a method similar to cuyler1's. The only real difference is that I use Marvel Mystery Oil, pour it in liberally through the spark plug hole, then replace the plug and let it sit for at least 24 hours before trying to turn the crank....gently, at first, using a back-and-forth motion. Once you feel the rings break loose, you should be able to feel whether it's somehow still bound up, but I've never had this stuff fail me completely! Good luck.

[cuyler1]

if this is an engine or vehicle you plan to keep then plan on a rebuild. 50 years of experience building,racing and hiding from the wife under a car. the "original" man cave dweller here!

[Frank S]

The a fore mentioned methods are tried and proven by many. However the pistons are not the only components which may cause an engine to be frozen in place.
the valve camshafts crank shaft bearings and even the lowly distributor or magneto are a few of the others. on small engines that have an alternator built right into the flywheel the magnets can become dislodged. Some small engines have counter rotating balance shafts which can drop a tooth from their gears. On motorcycle engines particularly those with chain driven overhead cams I've seen them drop chunks off of the chain guides which become lodged in the links of the chain and the sprocket on the crankshaft. These are some of the reasons to check everything before deciding on which procedure would best solve the situation.

[tonyfoale]

if this is an engine or vehicle you plan to keep then plan on a rebuild.

That would be my approach. If it is stuck then there is likely to be a reason that can't or shouldn't be fixed by external means.
BTW. where do you guys get all these stuck engines from?

[Shalen06]

Definitely an interesting tip/trick. Thanks. Although I have never had a fully seized engine i wanted to rescue, I have been partial to a 50/25/25 mix of acetone, atf and Seafoam (or Marvel's), in attempt to loosen stuck rings and carbon build up. Approx. 1/8 cup each cylinder and 1 to 3 days wait has helped me greatly. i can see how your grease gun approach may benefit, but i also would opt for using a spark-plug hole adapter to pressurize the cylinder after all pistons and rings have soaked.

[Diode2]

Get yourself some Penetrene and remove the spark plug, glow plug or injector. Pour a some Penetrene into the cylinder and let it sit. Penetrene is also extremely good for loosening seized or rusted parts. The grease gun or grease through the spark plug is a very good way to prevent the engine from seizing up if you know it's going to sit idle for a long time. Of course you have to remember you've done it when it comes time to fire the engine up. Cylinders full of grease will behave the same as one full of water and hydraulically lock. This could easily bend conrods.

[Ed ke6bnl]

I was watching a TV commercial for evaporust in cylinder to devolve rust then hit it with kerosene acetone power steering combo

[NortonDommi]

I've delt to quite a few seized engines. First determine if it is seized from sitting around, mechaniacl damage or mechanical damage then sitting around. Has it got water in the oil ect. ect. Filling it up with straight Diesel will test the crankseals plus displace water which can be dropped from sump or my lazy tube down the dipstick hole,(copper or Bundyworks), if petrol spark plugs out and equal parts mix of Kerosene/ATF/Hydrualic oil. Yes I know ATF & Hydrualic oil are essentially the same but most Hydrualic oils are Hydrophobic & ATF has gum solvents & detergents & the Kero is just a very light Diesel oil with great penertration. Anyway the three work well together & are not overly volitile.
Squirt some down each plug hole and let soak. Pressurising is good if the valves are seated but you need to be able to turn over to do each cylinder.
After a good long soak try and bar over. The flywheel ring gear is a good place. Try one way then the other. If no movement soak longer. When you get ANY movement bar it back & forth but not too aggressivley.
I've taken 2 -3 months to free up a badly seized engine, particulary bad if they have been shut off hot with heat seizure & parked up for a decade or two.
You might end up having to strip it down but if you can get things moving life will definately be easier for the effort.
I'm on month 4 of a Bedford 214 engine that has blown crankseals, blown head gasket & I suspect broken rings & at least three cracked pistons. I have a new engine but want to free up this one in the hope something will be salvageable, it has only just started to move and I just hate to be beat.