Campaign - Engine Cylinder Head Coolant Passage Blockage: Overview
NUMBER: 86-C-14GROUP: 6A-ENGINE
MECHANICAL
Date: OCTOBER, 1986
SUBJECT: ENGINE CYLINDER HEAD COOLANT PASSAGE BLOCKAGE
MODELS: 1986 S/T TRUCK AND M15 SAFARI VAN WITH 2.5L L4 GAS ENGINE (RPO LN8)
General Motors has determined that some 1986 GMC S/T15 Light Duty Truck and M15 Safari Van Models equipped with 2.5L L4 gas engines (RPO LN8) may have been produced with blocked cylinder head coolant passages. This condition can cause audible spark knock and/or engine overheating. To prevent the possibility of this condition occurring it will be necessary to inspect all involved vehicles for coolant passage blockage, and if a blockage is found, replace the cylinder head.