Piston rings

Before installing the piston rings, check the gaps in the locks of the rings. To check the ring lock clearance, remove the ring from the piston, insert it into the cylinder from above and push the piston into the lower part of the working area of the cylinder. Measure the gap in the ring lock with a feeler gauge. If the gap in the ring lock exceeds the allowable limits, then the piston ring must be replaced. If the gap in the lock of the ring is less than the required value, then it is necessary to file the end part of the ring with sandpaper or a file.

Check up backlashes in locks of piston rings for other rings.

Install piston rings to pistons. If rings are installed on the piston that used to be, then it is necessary to install them in their original places. When installing new piston rings, install them with the identification marks STD or TOP up the piston.

Attention. When installing the O-rings, do not interchange the top and middle O-rings. because they usually have a different profile.

When installing piston rings, the oil scraper piston ring is installed first, which usually consists of three separate parts.


On HCS and Endura-E engines, after installing the piston rings, position the piston ring locks as specified in the specifications.

On CVH and PTE engines, position the piston ring locks at a 120°angle.

On Zetec and Zetec-E engines, position the piston ring locks, including the oil scraper elements, evenly around the piston at an angle of 120°.