Pistons Are Rusted Stuck.

Got this 68 CJ5 that’s been sitting in a field for 35 years. Got the engine out and mostly disassembled but can’t get the pistons unstuck to remove them. Tried a number of solvents. What works best?

 

I made a piston driver just for this.

 

Soaking with a mix like Warloch said works well. PB Blaster, Zep Super Penetrant, etc. works pretty well too. Soaking and patience and more soaking is key. Some force on the pistons with a driver will most likely be necessary. A strong hardwood block of wood works well here.

 

I made a mix of ATF, Diesel Fuel, and Marvel Mystery Oil just what I had on hand. Time is your friend. I let it sit with a pan underneath. That took a week. When it filtered through, I picked up the pan and put it back through. One piston would not free up.
Cut a round piece of plywood and beat it back and forth with a piece of 2X4. Still couldn't get it out.

Finally got some dry ice and packed the cylinder with it and then was able to drive it out.

Took a while but I was more stubborn than that engine.
Still have to put it all together.


Dave

 

Thanks for the posts. Guess I’ll have to learn some patience!

 

My dad helped me once with this, and besides oil, he used very hot water to fill the cooling passages. Then a piece of wood in the bore, and a sledgehammer. It worked.

 

I like the sledge hammer idea. I’ll try with wood first though.

 

Freed up a lot of stuck engines using Marvel Mystery Oil, sometimes kerosene mixed with automatic transmission fluid. Pour some in and let it soak a few days or a week, then I use a piece of hardwood, mine is a chunk of hickory, and a small sledge hammer. I give each piston a few whacks every few days which usually always frees them up, but a couple of times I have had to use an air impact hammer. Pistons are usually toast anyway.

 

I got it freed up with a round piece of plywood, a piece of 2X4 and a small sledge hammer. Didn't want to score the cylinder.
Read an article of a guy restoring an old WWI truck. He drilled into the pistons since it had been sitting outside for 70 years then driving them out collapsing them.
It just takes patience. I would pour the mixture over the cylinders at night, in the morning before I left for work and at night after I got home.
Took more than a week but I got it free.


Dave

 

Don't strike the piston directly with a sledgehammer! Use a block of wood in the bore, strike the wood. And use reasonable care with the force applied...

In my case the pistons were actually cast iron, in a 1925 Ford.

 

all of the above, and my drive was a piece of white oak turned just under piston diameter and cut a con cave in the end so most of the force was on the outside of the piston....patience and lots of soaking, never tried it but like the idea of filling water jacket with hot water

 

If they are aluminum pistons, just smash them out. I've had to do that several times. On my antique engines with cast pistons, a block of wood and a hammer will do.

 

Soaking the piston got it free.
Dry ice got it to drive out the bottom of the engine.

Dave

 

Kroil is your friend

 

If they are stuck that hard your going to need to bore the cylinders out anyway no need to be delicate

 

Not sure what engine you have. Had a stuck engine once that standing on a wrench with a 3 foot extension would not turn. Thought the
crank bolt would strip or round off. Soaked with everything including Seafoam. Hit each cylinder with some air every few days to to coat
around the cylinders. An adapter from my air hose to a spark plug hole worked for me, but the heads were still on. I was amazed what
180 psi would do.

 

Thanks all. Got them all unstuck and you're right, I'll have to have the block bored and cleaned anyway. No cheap fixes here. I'll have to totally overhaul.

 

You don't mention the engine, but assuming 3.5" bore each piston has 9.62 square inches of surface area. 180 psi X 9.62 = 1732 lbs of pressure on the piston!
Does your compressor really produce 180 psi?

 

Made me look! Yes 180PSI. It is a 5hp 2-stage with a 60 gallon tank. It is a Sanborn model with a 200PSI working limit. Pressure relief set at 200PSI to open and 152 PSI to close. One of my better
purchases picked up from Price Club almost 40 years ago. Back when Price Club carried Armstrong Tru-Trac tires. Beat the crap out it. Plumbed my shop to have air where needed and located in my
storage room to keep the noise level down. I change the oil periodically and replaced the motor bearings once. I believe the belts are original unless I did them with the bearing change. Don't really
remember as I have changed thousand of belts over the years and can't remember all of them. The oil looks a little low, so thanks for making me look! I did a/c and refrigeration and controls for 40
years. Repairs and installation from water coolers, ice machines, block ice plants for ice carvings, aircraft ground units, boilers, auto, cascade systems to -180 degrees, warehouses that semis could drive into,
cooling towers, 200 ton chillers and more.
If it cooled I worked on it day or night as product would go bad if too warm. Some systems run at 450PSI. I have 2000PSI nitrogen tanks used for pressure testing lines and systems.

The engine was a 225 V6 bored .060 making the bore 3.810. Got it running, then went ahead and put a good cross hatch hone job, gapped and replaced the rings. This is just under the 3.820
that the 231 oddfire uses and has me questioning how much the 225 can be bored. I also have brain that never really turns off and stayed up late to catch up on "Yellowstone" and "1923".
I highly recommend both and they are written by Taylor Sheridan who had a bit part as a sheriff on "Sons OF Anarchy". Never was a Cole Hauser fan but he does a great job as Rip.

So, 1732 PSI on a piston. What do you imagine the explosions happening in a cylinder produce and do you have any other thoughts the idea for freeing a stuck engine? I felt I was running
out of options with out doing major damage and wanted to be sure the engine was salvageable before moving forward. TLDR.