35. Piston, Connecting Rod, and Bearing Cleaning and Inspection
PISTON, CONNECTING ROD, AND BEARINGS CLEANING AND INSPECTIONPISTON AND PIN AND PISTON RINGS
IMPORTANT:
- Replace the pistons and the pins that are damaged or show signs of excessive wear.
- The piston and the pin are a matched set. If service is required, replace the piston and the pin 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.
1. Clean the varnish from the piston and the pin with cleaning solvent.
CAUTION: Wear safety glasses in order to avoid eye damage.
2. Dry the components with compressed air.
3. Clean the piston ring grooves with a suitable ring groove cleaning tool.
4. Clean the oil lubrication holes and slots.
5. Inspect the piston and the pin for the following:
- Cracks in the piston ring lands, the piston skirt, or the 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 piston pin bore (3) or the piston pin
6. Identify the NEW upper and lower compression rings. The upper compression ring can be identified by a paint mark (3) located 180 degrees from the end gap. The lower compression ring can be identified by a paint mark (3) located 90 degrees from the end gap. Both rings should be installed with the orientation marks (1, 2) facing the top of the piston.
7. 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 a distorted piston ring groove, MINOR ring groove imperfections may be removed with a fine file. If binding is caused by a distorted piston ring, replace the piston ring.
8. 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, pin and connecting rod assembly. Refer to Engine Mechanical Specifications (LQ4 VIN U).
9. To determine piston pin-to-bore clearance, use a micrometer and measure the piston pin outside diameter (OD).
10. To determine piston pin-to-bore clearance, use an inside micrometer and measure the piston pin bore inside diameter (ID).
11. Subtract the piston pin OD measurement from the piston pin bore ID measurement to determine pin-to-bore clearance. Refer to Engine Mechanical Specifications (LQ4 VIN U).