Engine - Metallic Knock Noise When Cold, Piston Slap
Bulletin: 92-6-21Date: June '93
Ref.No.: 92-349-6
Corp.Ref.No.: 376004
SUBJECT:
METALLIC KNOCK SOUND WHEN ENGINE COLD (REPLACE PISTON/ENGINE)
MODELS AFFECTED:
1991-92 ROADMASTER WITH 5.7L (L05) ENGINE
CONDITION:
Some owners of 1991-92 Roadmasters equipped with 5.7L V8 engines (RPO L05 - VIN 7) may comment of engine cold "piston slap" noise. This bulletin covers all 1991 and 1992 production through May of 1992.
NOTE:
This noise will not result in engine failure, but may be a customer annoyance condition.
Engine cold "piston slap" may be described as:
A metallic "knock" sound that diminishes as the engine warms up. The knock sound is most noticeable at 1500 through 2000 engine RPM, with the engine at a light load. Duration of the "knock" varies depending on the engine block temperature. Temperatures of 40 degrees F or less may result in a knock duration as long as 5 to 8 minutes. Intensity of the knock will be dependent upon the piston/cylinder bore fit and block temperature.
CAUSE:
Improper piston/cylinder bore fit.
CORRECTION:
Verify that the "piston slap - engine cold" condition is correctly identified.
Two methods of resolving this problem are available.
Preferred Method:
A 5.7L V8 (VIN 7) "Goodwrench" Engine Assembly (for passenger car application only) has been released to address this concern:
Description Part Number
5.7L V8 Goodwrench Engine 12513151
Assembly (Passenger Car)
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
Use current published Labor Operation Numbers.