# Clean a rusty cylinder...



## daedwards0956 (Mar 1, 2016)

I have just pulled the cylinder from a gravely convertible hopefully in prep for getting an exhaust flange repaired.

What's the best way to try and remove rust from the cylinder for a general cleanup??

Thanks
dan


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## RC Wells (Dec 26, 2008)

If the rust is light and has not pitted the iron cylinder wall it can be easily cleaned with penetrating oil and a rag. Just clean it enough to make the surface slick, then let the engine clean the rest of it by running. If you have pulled the piston and the rings are frozen into the grooves, then it will be necessary to free them and to just make sure the piston walls are slick, they do not have to be shiny, just not covered with loose rust. If the piston is not pulled from the engine, and you have compression once the rust on the cylinder walls is slicked down, wobble the piston as much as you can to make sure the rings are free, then just let it run at a high idle, not full throttle, and it will clean out the remaining rust.

Change the oil frequently when cleaning out the rust by running the engine.

Heavy rust that has pitted the cylinder walls means the engine will need to be rebored and an oversize piston installed. The roughness will not allow the engine to hold compression and will erode the piston until it fails.


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## daedwards0956 (Mar 1, 2016)

*Should have been more specific*

The inside of the cylinder is fine.
It's external rust on the fins and around the intake and exhaust flanges, basically the whole outside.

Want to clean it up before I, hopefully, get the exhaust flange repaired.

I will hone the cylinder enough to smooth it and will measure to see if I need oversized rings for replacement before I reassemble.


dan


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## RC Wells (Dec 26, 2008)

Just get some Navel Jelly and brush it on the external rust, then let it work. Rinse off the results and then coat any remaining rust with a solution of phosphoric acid, generally sold as Rust Killer or such at most auto parts stores. Then when all is clean and dry, prime and paint with a heat resistant product.


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## jhngardner367 (Apr 5, 2011)

Are we talking of an engine cylinder,or a hydraulic cylinder,and inside,or outside?
Cancel that,....just saw the second post.


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