Engine - Knock, Rattle, or Tap Noise: Overview
File In Section: 6 - EngineBulletin No.: 77-60-01A
Date: July, 1997
Subject:
Knock, Rattle, or Tap Noise from the Engine Before the Engine Has Reached Operating Temperature or Under Light Load Conditions at Operating Temperature (Replace Piston and/or Rod Assemblies)
Models:
1994-96 Buick Century
1994-96 Chevrolet Beretta, Corsica
1994-97 Chevrolet Cavalier
1994-96 Oldsmobile Ciera
1995-97 Pontiac Sunfire
1994-97 Chevrolet and GMC S Models
with 2.2L Engine (VIN 4 - RPO LN2)
This bulletin is being revised to add plants to the VIN chart below for Cavalier and Sunfire, to add a "Notice" statement to step three (3) of the correction and to add coolant fill information. Please discard Corporate Bulletin Number 77-60-01 (Section 6 - Engine).
Vehicles Involved:
Involved are certain 1994 through 1997 A Car, J Car, L Car, S Trucks and Jimmys equipped with LN2 engines and built within the following VIN Breakpoints:
Important:
Canadian dealers must have PRIOR approval from their District Service Manager for each individual engine repair described in this bulletin.
Condition
Some customers may comment of a knock, rattle, tap, or tick noise from the engine before the engine has reached operating temperature. The noise may also occur at operating temperature under light load or deceleration conditions. This noise does not result in any damage but may be objectionable to some customers.
This noise should not be confused with other sources of noise such as accessory drive ticks, exhaust system rattles, clutch or flywheel noise, etc.
Cause
The cause is a rocking motion of the piston in the bore that can occur, under certain conditions.
Diagnosis
If possible, have the customer leave the vehicle overnight to allow the engine to stabilize at ambient temperature. Start the vehicle and as soon as possible, operate the engine between 2000 and 2200 RPM. If necessary, on automatic transmission equipped vehicles, shift the vehicle manually into 1st or 2nd gear to maintain the RPM range.
Caution:
In manual 1st or 2nd, the vehicle may not be able to maintain normal traffic speed within the range between 2000 and 2200 RPM. Be aware that other drivers may not be prepared for a vehicle traveling at a much slower speed. If possible, attempt to go to a rural area or to an area that has light traffic.
The noise may be louder if the ambient temperature is cooler and will be much less noticeable with the engine at operating temperature.
Warranty Information
For vehicles repaired under warranty, use the table.
Parts Information