Piston Ring: Service and Repair

Reconditioning

Replacing the piston rings
A corrective action is to replace the two lower piston rings (scraper ring and oil ring).

If the upper piston ring (compression ring) is undamaged it must not be replaced. Increased oil consumption may result if the compression ring is replaced.

Caution: Check that the upper piston ring (compression ring) is the correct way round (see below)!

It is important that the uppermost and centre rings are installed the correct way up.

The lower ring can be installed any way up.

Distribute the piston ring openings as follows.

Early version

A. Compression ring





This is marked with text or with a circle. The marking must be facing upwards! It may be difficult to read the text, a magnifying glass may be required.

B. Scraper ring
The cut out must be turned downwards. The text must be on the top of the ring.

C. Oil ring
Earlier versions of the oil ring are not marked and can be installed any side up.

Later versions of the oil ring are divided into 3 sections. These slotted rings can be installed with either side facing up.

Caution: New versions of the piston ring assembly cannot be combined with earlier versions of the piston!

Late version





Conclusions for corrective action

Replacing the piston rings
As a first corrective action the piston rings should be replaced. Normally only the scraper ring and the oil ring must be replaced. The compression ring should only be replaced if absolutely necessary.

Replacing valve stem seals
If traces of oil are found on the valve crowns, in the ducts or on the valve stems, the valve stem seals should be replaced.

Thoroughly check the cylinder head. Check for internal leakage.

Replacing the cylinder head
If traces of oil (described above) are found and faults are found on the cylinder head, internal leakage for example, the cylinder head must be replaced.

Replacing the cylinder block and pistons
If damage is found in the cylinder block (worn cylinder bore, deep scratches etc.) the cylinder block, pistons and piston rings must be replaced.

Replacing the engine
The engine must be replaced if the problem cannot be remedied using the above corrective actions.