Piston, Pin, and Piston Rings
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Replace pistons, pins, and connecting rods that are damaged or show signs of excessive wear.
- The first design press-fit piston, pin, and connecting rod 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.
- Dry the components with compressed air.
- Clean the piston ring grooves with a suitable ring groove cleaning tool.
- Clean the oil lubrication holes and slots.
- 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
- 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.
- 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.
- Measure the piston ring side clearance with a feeler gauge. If side clearance is not within specifications, try another piston ring. If the proper ring-to-groove clearance cannot be obtained, replace the first design press-fit piston, pin, and connecting rod assembly. Refer to Engine Mechanical Specifications (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .
- To determine piston pin-to-bore clearance, use a micrometer and measure the piston pin outside diameter (OD).
- 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 (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .
IMPORTANT:
CAUTION:
Wear safety glasses in order to avoid eye damage.