Subject: Water Pump Bearing and/or Shaft Failures
Model and Year: V-8 Engines with Fan Clutch
Source: Chevrolet Dealer Service Technical Bulletin
Bulletin No: 71-T-37
Date: June 23, 1971
TO: ALL CHEVROLET DEALERS
Investigation has shown that water pump bearing and/or shaft failures may occur if excessive run-out exists at the fan clutch.
Interim 1970, two (2) modifications were made in an effort to maintain total run-out within .006 inch.
For service, since excessive run-out could be induced when the water pump, pulley and/or fan clutch is replaced and randomly assembled, the following procedure has been developed. Use of this procedure will indicate run-out and provide a method of correction if it is excessive.
Chevrolet Motor Division
General Motors Corporation
During replacement of the water pump or related parts, the water pump pulley should be inspected to determine if the pulley has a reinforcement on the surface which contacts the water pump hub. Pulleys with a welded reinforcement should be replaced with a 1971 pulley (refer to chart). All mating surfaces (Water pump hub and fan clutch hub) should be inspected for smooth mating surfaces and reworked as necessary. Except for the fan belt, components should then be assembled to the engine as specified in Section 6K of the Chassis Service Manual. Check radial run-out according to the listed procedure below.
During replacement of the water pump on trucks, the pulley should be inspected for a loose reinforcement (cracked weld) and replace if necessary. Inspect for smooth mating surfaces (water pump hub and fan clutch hub) and rework as necessary. Except for the fan belt, components should then be assembled to the engine as specified in Section 6K of the Chassis Service Manual. Check radial run-out according to the listed procedure below.
Procedure for Indicating Radial Run-Out
Bolt Torque Sequence
F. Recheck total indicator run-out to verify that run-out is within .006 inch. Install fan belt and adjust.
Article ID: 1020
Created: November 29, 2014
Last Updated: November 29, 2014
Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article/1970-corvette-service-bulletin-water-pump-bearing-and-or-shaft-failures-1020.html