Question:
It’s a lovely site and easy to understand for people who are not mechanically inclined. My garageman said one of the pistons is cracked and therefore he must change all the pistons. Is that true? Why not just change the one that’s cracked?

Thank you,
Mrs. A

Answer:
It is general practice to change all the pistons at once. If one piston is cracked, there is a good chance the others will crack in short time. When replacing the piston, the cylinder walls sometime need to be remachined, and at least honed, to allow the new rings to seat. It is important for the rings to seat properly or your engine will not have good compression and may burn oil. The labor to replace one piston or all of them is not much more, and the pistons are generally purchased in sets, so his advice to replace all pistons is good.

Kevin