Piston, Pin, and Piston Rings

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: View Of Piston & Connecting Rod Components

Courtesy of GENERAL MOTORS CORP.

IMPORTANT:

Replace pistons, pins, and connecting rods that are damaged or show signs of excessive wear.
The piston and pin are to be serviced as an assembly.
Do not wire brush any part of the piston.
Measurement of the components should be taken with the components at normal room temperature.

Clean the varnish and carbon from the piston (1) using cleaning solvent.

CAUTION: Refer to Safety Glasses Caution in Cautions and Notices.

Dry the components with compressed air.

Fig 2: Cleaning Piston Ring Grooves With Suitable Ring Groove Cleaning Tool

Courtesy of GENERAL MOTORS CORP.

Clean the piston ring grooves with a suitable ring groove cleaning tool.
Clean the oil lubrication holes and slots.

Fig 3: Identifying Piston Damage Inspection Areas

Courtesy of GENERAL MOTORS CORP.

Inspect the piston for the following conditions:
- Cracks in the piston ring lands, the piston skirt, or pin bosses
- Piston ring grooves for nicks, burrs, or warpage which may cause the piston ring to bind
  MINOR imperfections may be removed from the piston with a fine file.
- Scuffed or damaged skirts (2)
- Eroded areas at the top of the piston (1)
- Scoring to the full-floating design piston pin bore (3) or piston pin

Fig 4: Inserting Piston Ring Into Ring Groove

Courtesy of GENERAL MOTORS CORP.

Insert the edge of the piston ring into the piston ring groove.
Roll the piston ring completely around the piston. If binding is caused by distorted ring groove, MINOR imperfections may be removed with a fine file. If binding is caused by a distorted piston ring, replace the rings, as required.

Fig 5: Measuring Piston Ring Side Clearance

Courtesy of GENERAL MOTORS CORP.

Measure the piston ring side clearance with a feeler gage. If side clearance is not within specifications, try another piston ring. If the proper ring-to-groove clearance cannot be obtained, replace the piston and pin as an assembly. Refer to Engine Mechanical Specifications .

Fig 6: Measuring Piston Pin Diameter

Courtesy of GENERAL MOTORS CORP.

To determine piston pin-to-bore clearance, use a micrometer and measure the piston pin outside diameter (OD).

Fig 7: Measuring Piston Pin Bore

Courtesy of GENERAL MOTORS CORP.

To determine the piston pin-to-bore clearance, use an inside micrometer and measure the piston pin bore inside diameter (ID).
Subtract the piston pin OD measurement from the piston pin bore ID measurement to determine pin-to-bore clearance. Refer to Engine Mechanical Specifications .