Engine - Whirling Sound From Lower Rear

Bulletin No.:
00-06-01-001

File In Section:
06 - Engine/Propulsion System

Date:
February, 2000

Subject:
Engine Noise (Check/Replace Crankshaft Position Sensor)





Models:
1999 Chevrolet and GMC C/K Models (Silverado and Sierra) with 4.8 L or 5.3 L V8 Engine (VINs V, T - RPOs LR4, LM7) Built within the VIN breakpoints shown in image.

Condition

Some customers may comment on a whirling sound from the lower rear side of the engine. This occurs as the engine warms up, between 1500 and 2000 engine RPM. The sound may not be present on a cold engine.

Cause

The crankshaft position sensor may be making contact with the reluctor ring.

Correction

IMPORTANT:
Dealers may encounter a few vehicles, shipped from the vehicle assembly plants, which have a 2nd rubber 0-ring installed over the crankshaft position sensor, and a copper shim under the mounting tab.





1. Remove the crankshaft position sensor (1), and check for witness marks caused by contact with the reluctor ring. Reference the Service Manual procedure as needed.

2. If no witness marks are evident on the crankshaft position sensor (1):

IMPORTANT:
Do not place an additional shim washer (2) on the crankshaft position sensor (1), if one was not previously installed.

2.1. Reinstall the original crankshaft position sensor (1) with any 0-rings and shims that may have been previously installed.

Tighten

Tighten the mounting bolt (4) to 25 Nm (18 lb ft).

2.2. Continue with standard diagnostic procedures.

3. If witness marks are evident on the crankshaft position sensor (1):

^ If a shim washer and/or 0-ring had been previously installed: call Technical Assistance for additional instructions

^ If a shim washer and/or 0-ring is not present:

3.1. Place a shim washer (2) P/N 12565102 on a new crankshaft position sensor.

3.2. Install the new crankshaft position sensor (1) with the mounting bolt (4).

Tighten

Tighten the mounting bolt to 25 N.m (18 lb ft).

3.3. Perform the Crank Angle Sensing Error (CASE) re-learn procedure.

3.4. With the engine at operating temperature, verify the correction of the noise condition.





Parts Information

Parts are currently available from GMSPO.





Warranty Information

For vehicles repaired under warranty, use chart.