Engine - High Temperatures/Overheating
Number: 84-110Section: 6B (VI)
Date: April, 1984
Subject: POSSIBLE HIGH ENGINE TEMPERATURE
OR OVERHEAT CONDITION
Model and Year: 1980-84 SERIES 10 THRU 60 EQUIPPED
WITH MARK IV 366, 427, AND 454 ENGINES
TO: ALL CHEVROLET DEALERS
When diagnosing for a possible high engine temperature or overheat condition on Mark IV engines, refer to the Shop Manual Engine Cooling Diagnosis Section. If the condition cannot be resolved by normal diagnosis procedures, check the cylinder head coolant passages for possible blocked cavities.
To make this inspection, it is not necessary to remove the cylinder head from the engine. Only the removal of the intake manifold is required.
Casting flash on a Mark IV head may leave barrier or envelope through the middle of the head at the core parting line.
With the intake manifold removed, inspect the coolant passages at both ends of the cylinder head. If the passages are not clear and excessive casting flash or walls are observed, replace the cylinder head. This condition may be found on replacement cylinder heads so be sure to inspect the new cylinder head prior to assembly.