How to Polish a Crankshaft

A crankshaft is the part of a combustion engine that is responsible for converting the energy of the pistons. Crankshafts are made up of crankpins, main journals, crank webs and counterweights. Paying for crankshaft repairs can be pricey, which is where DIY crankshaft repairs come in handy. The better you take care of your crankshaft though, by polishing, the less frequent repairs will be.

Polishing your crankshaft is important for engine performance. Tackling a DIY crankshaft polish job is a balancing act. You want to get the shaft well polished and clean without interfering too much. In order to work, an essential function of the crankshaft is its ability to work with the journal. When you overpolish, the crankshaft risks skipping and a skipping crankshaft can be dangerous. After you polish the shaft, be sure to watch for signs of problems or a bad crankshaft sensor for a few days.

Clean a workspace in your garage or work area and gather up all of your supplies before you begin the process. You will need two-hundred grit sandpaper and a shoelace to start.

Removal

If you want to get a full clean and polish, you will need to take the crankshaft out of the engine. As you remove the shaft, look for grooves in the head and examine the shaft as a whole. Once the entire shaft is out, set it down on a clean workspace very carefully.

If needed, have someone help you measure the grooves in the head to determine the right size of sandpaper to use. Then, cut the two-hundred grit sandpaper to fit into the grooves on the head of your crankshaft and use that paper manually to shine and buff the space. Go slow and work carefully.

Sanding

Now take your shoelace and tie it around the head of the shaft. Make sure that the lace weaves back and forth over the head to give you the most secure hold. After everything appears to be woven in the right place, hold both ends of the shoelace and slowly pull each end in opposite directions. The more you pull at the shoelace, the easier it will be to tug it from side to side.

This is a good sign. As soon as you can feel that there is barely any resistance in the lace left, stop and examine the head of the crankshaft. If it looks good to you, then you are good to go.

If you’re looking for a little extra shine on the shaft though, take your shoelace and use it for this handy hack. Take a piece of your silicon carbide sanding paper—preferably cut wet/dry—and cut it into strips of the desired width. If you’re using this method to shine up the journal, cut them into strips the width of the journal. Then soak the strips in kerosene for about five minutes.

Take those strips and wrap them around the shaft. Secure the wrapped strips buy wrapping your shoelace over the top a few times. You will end up with one end of the lace in each hand. Then simply pull the lace from left to right and shine the shaft. It’s a simple way to get a great shine without having to pay for expensive power tools.

Reinstall

Details are your friend when you’re putting a crankshaft back into a car or motorcycle. The crankshaft is one spot where car detail is very important and if you don’t get the shaft back in just right, you can cause major problems. Measure the shaft and then measure it again.

Get a good measurement of the head to make sure that it’s going back into the right spot on the right side of the car. You risk grinding the gears and head when you place the shaft back in too quickly or wrong, which could ultimately result in the need for a new shaft.

After you’ve reinstalled the shaft, give the whole thing a test drive or start. You’ll know pretty quickly if your DIY crankshaft shining was a success.