When you are working on your engine and replacing the head gasket and you will need to clean your deck surface before you install the new gasket this is a good time to clean up any carbon buildup that might be on the top portion of your cylinder walls and the top of the pistons.
While doing so you will also be able to inspect the cylinder walls and deck and know if you need some machine shop time.
The reason you really want to take the time to do this is that carbon buildup in these areas can cause hot spots in your combustion area. This is really all we are doing is cleaning the combustion area and you should be careful not to score, scrape or cause any damage to the area of your cylinder wall where the piston rings ride.
If the engine is pretty fresh then you should still see a cross hatch in the cylinder where the pistons ride. This crosshatch is put in the cylinder wall with a hone. If you are not disassembling the engine you really don’t want to hone the cylinder walls for any reason. If you cause a scrape in this area you are being way to aggressive during the cleaning process.
Carbon buildup is pretty easy to remove. It will probably be easier to remove than cleaning the deck surface or just about the same.
When you are working in this area you don’t want to use aggressive tools or sandpaper all you need to use is a scotch brite scrubbing pad without abrasive and some light oil like CRC or WD40.
Can Scotch Brite Pads Cause Engine Damage?
Some guys like to break out the scotch brite wheels and a die grinder to clean the deck and tops of the pistons but if you are not disassembling the engine completely and reinstalling new bearings after a through wash down then this is really not a good idea. The reason is that these pads and disks more often than not will contain an abrasive that can get in your bearings.
Some people can get away with this but often it will mean a shorter life of your engine. You can even void your engine warranty.
Additionally using a die grinder on these parts is really not smart because they are pretty aggressive and can cause divots and scratches that will require machine shop time to repair.
If you are going to use a scrubbing pad you want to use a Nylon Pad that has no abrasive and one that won’t easily fall apart and end up in your oil. Lightly scrubbing with a cheap household pad you can get at the dollar store in a 5 pack is not the worst idea when you compare it to everything else.
Using Scrapers To Clean Your Engine Deck
The use of razor blade and other scrapers on your engine should be done with the same care and precaution as scotch brite pads. They can cause gouges and problems instead of curing them.
Some mechanics use special plastic scrapers along with light oil or deck cleaner to remove particulate. Gasket Cleaner can do a lot. Other mechanics make scrapers out of soft metal like copper by taking a piece of copper pipe and shaping it into a scraper. This is not the worst idea to use a softer metal on a harder metal but you have to use care.
Cleaning after you Remove the Carbon and Gasket Buildup
After you remove all of the surface debris and buildup that you can you should take special care to wash down your parts with a non chlorinated cleaner and then apply a light oil until you are ready for assembly. You should also cover your engine with something to reduce the chance that debris from other areas can get into it. I personally like to use plastic wrap because it conforms to shapes well and will protect from debris and from liquids. A few sheets of plastic wrap that are then covered with a shop cloth will protect your work until you are ready to continue.
Final Note
There is a lot of conversation about the use of Scotch Brite pads on engine decks and combustion areas but you have to use some method. If you are in doubt take precautions and contact manufacturers about what products should be used.
There are many professionals that will even ball hone an engine cylinder while it is in the car to remove this build up on combustion areas and others that have no problems using aggressive methods of cleaning but they have been trained on what to do and how much they can get away with without causing damage.
The information provided in this how to should not be thought of as the only and best methods to perform work on your engine. It is up to you to do your research and ask questions from other sources.