Engine - Overheats During Heavy Usage: Overview

91CHEVY02

Number: 91-145-6B


Section: 6B


Date: December 1990


Corporate Bulletin No.: 066203


Subject: ENGINE OVERHEAT WHEN TOWING OR DURING HEAVY USAGE


Model and Year, 1988-91 C/K TRUCKS WITH 5.7L ENGINE


TO: ALL CHEVROLET DEALERS


Some 1988-91 C/K trucks equipped with 5.7L engines may experience an engine overheat condition (245 degrees F - 260 degrees F) while towing a trailer or under heavy usage, yet during normal operation, without heavy load or trailer, the engine operates at a normal temperature (210 degrees F - 235 degrees F).


If this condition is encountered and cannot be repaired using procedures in the service manual, a larger capacity cooling system may be installed. This larger capacity cooling system typically reduces engine operating temperatures by 20-25 degrees while towing a trailer or under heavy usage.


IMPORTANT: This larger capacity cooling system is not intended for correcting engine overheats that occur while idling or under normal operating conditions.


NOTE: Installation of this larger cooling system requires that the radiator core support opening be modified as outlined in Dealer Service Bulletin No. 88-338-6B.


It will be necessary to install new engine oil cooler hoses on models equipped with an internal (inside radiator) engine oil cooler.

On models with an externally (outside radiator) mounted engine oil cooler, the installation will require the removal of the external oil cooler and hoses. They will be replaced by the internal (inside radiator) engine oil cooler, which this larger capacity radiator features, and the required oil cooler hoses.