Cleaning and Inspection
CLEANINGCAUTION: Do not use a caustic cleaning solution or a wire brush to clean pistons or damage may occur.
Using a gasket scraper, remove deposits from the piston surfaces. Clean gum or varnish from the piston skirt, piston pins and piston rings with solvent.
CAUTION: Do not scratch coating on piston skirt.
Clean the piston ring grooves with Piston Ring Groove Cleaner 303-D033 (D81L-6002-D) or equivalent or a broken piston ring. Make sure oil ring slots (or holes) are clean.
INSPECTION
Carefully inspect the pistons for fractures at the ring lands, skirts, oil ring slot corners, and pin bosses. Also inspect for scuffed, rough or scored skirts. If the lower inner portion of the piston ring grooves has a high step, replace the piston/rod/pin assembly. The step will interfere with piston ring operation and cause excessive piston ring side clearance.
Spongy, eroded areas near the edge of the top of the piston are usually caused by detonation or preignition. A shiny surface on the thrust surface of the piston offset from the centerline between the piston pin holes or a sideways wear pattern on the skirt, can be caused by a bent pistons. Replace the piston/rod/pin assemblies that show signs of excessive wear, wavy ring lands or fractures or damage from detonation or pre-ignition.
Check the piston-to-cylinder bore clearance by measuring the piston and bore diameters. Measure the outer diameter (OD) of the piston and check the piston ring side clearance following the procedure under Piston Rings-Fitting.
Replace the piston/rod/pin assemblies showing signs of fracture, etching or wear. Check the piston pin fit in the piston and connecting rod.