How to loosen stuck rings

[Old buicks 2]

Have 14 Overland with two cylinders that apparently have stuck rings.   Compression test showed 0 on these two holes.   I lapped the valves and now have 15 lbs of compression.   Really don't want to remove and rebuild if I don't have to.    The engine does run but has little power.   The other two cylinders show 50+lbs each

[edinmass]

Could be cracked rings……you can’t assume stuck. Usually stuck rings release quickly. Soak them for a week with your favorite concoction, and then run it. If they don’t free up in fifteen minutes, pull it apart. Unfortunately, there is no free lunch. You could also pump 180 degree water through the block while letting it soak…….thenheat helps.

[Rusty_OToole]

I was going to suggest filling it with thin oil (like 10W30) and going for a long drive. A shot of Rislone, Bardahl, MMM etc might help.

[Jim Bollman]

I use a 50:50 mix of kerosene and Marvel Mystery Oil.  Squirt some in and let it soak a few days,  crank it over and repeat till I have enough  compression to get it started.  Then run till warm and then squirt more mix in and let it set a few days and repeat.

[Larry Schramm]

I would squirt some 50:50 solution of acetone & automatic trans fluid and let it sit for several days.

[JustDave]

When I was a teenager my dad had a flathead ford with stuck rings my dad being an old country boy took out the spark plug of the offending cylinder he then started the motor let it run for about to minutes put the plug back in he said later in the week problem solved I can’t guarantee this. Is a good idea.        Dave

[wayne sheldon]

Several similar concoctions might work? Or not. Try one, then maybe another. Sometimes one will work, and others may not. Both flow characteristics and chemical interactions vary and affect which will or won't work from one car to another.

Allowing the concoction to sit for several days also might help.

 

One serious caution however. While various thinned penetrative oils might free up the rings? And running the engine might help speed up the process in freeing the rings? Do not run the engine long or hard with too little real oil in it. Those thinned concoctions do not cushion and protect the bearings enough. 

Operating temperatures will help. Putting warm, then hot water into the radiator and engine can raise the engines temperature to near operating range without damaging bearings, then the vibration and motion of idling the engine for a few minutes might be enough to free up the rings. 

 

If the first cycle doesn't do it? Try again, and maybe even again again.

 

On the other hand? Sometimes the only thing that might do the trick is a complete teardown.

 

If the rings do free up a bit, and compression gets better but not all the way up? An old trick is to blow some Bon Ami sink cleanser through the intake while running. Bon Ami is a very fine abrasive sink cleanser, and can break down the cylinder glazing once the rings have freed up.

 

Bon Ami is a good friend.

 

 

Edited August 18 by wayne sheldon
I hate leaving typos! (see edit history)

[Mark Wetherbee]

14 hours ago, Larry Schramm said:

I would squirt some 50:50 solution of acetone & automatic trans fluid and let it sit for several days.

I call this mix cough syrup and it does a good job. I put a quarter cup in each cylinder of the 13 Buick I  just bought and it definitely helped. I’ve also used ATF and carburetor cleaner mixed for things that have carbon buildup but it evaporates quickly so it works better if you can seal it in.

[60FlatTop]

LOng term stored cars seem to gravitate to me. On multi-cylinder car that have set idle for periods I find that stuck or compressed rings occur base on where the rings sat relative the the taper of the bore wear. Those pistons at the lower point of the stroke where the wear is less will have the rings  compressed into the ringlands. There is also a higher risk of scaly rust in these bores due to open valves a the entrance of airborne moisture. Even a slow revolution can embed that grit into the rings.

 

Well lubricated and careful initial revolution can prevent major damage but I have still found low compression on the group of cylinders at the low point of their stroke. Once spinning freely the car can be driven about 200 miles an the rings will free up. The compression will be equal. I have a friend who has repeatedly let his Hudson 8 sit over the past 50 years and always brings it to me to recommission. It does that.

 

Previous wear, unprepared storage, and uncontrolled condensation are the three big players with stored cars. Even if you gently work through the scale on the cylinder walls there can be pits that trap oil that will burn and smoke on the combustion stroke.

 

Low compression and low cranking vacuum may cause the need for the car to be fuel primed during the initial driving starts but it will recover. If it doesn't smoke that is great. Otherwise you will be honing those pit off the cylinder walls.

 

Last week my nephew stopped by to borrow my flywheel turning tool. I inherited a 1940 Buick Roadmaster stored since 2007 from his father-in-law. He left with lots of cautions to go with that tool.

[mechanician]

I don't think I have ever pulled apart a long-sitting brass era engine where I didn't find something that was going to bite me later.  Take it apart and clean it up. If there's nothing wrong its not a rebuild, just a cleaning, if there is it is easier than after the engine internals seek daylight...

[JFranklin]

34 minutes ago, mechanician said:

I don't think I have ever pulled apart a long-sitting brass era engine where I didn't find something that was going to bite me later.  Take it apart and clean it up. If there's nothing wrong its not a rebuild, just a cleaning..

In the mid 60s my mechanic mentor bought a factory new engine for a '36 Chevrolet I now own and completely disassembled the new engine. He showed me a piston ring that was installed upside down! So I agree to take a look on unknown mechanical parts.