Exhaust System - Buzz/Rattle/Exhaust Noise

Article No.
03-19-9

09/29/03

^ ENGINE - 4.0L SOHC - BUZZ, RATTLE, OR
EXHAUST NOISE FROM UNDER THE BODY

^ NOISE - BUZZ, RATTLE, OR EXHAUST NOISE
FROM UNDER THE BODY - VEHICLES EQUIPPED
WITH 4.0L SOHC ENGINE ONLY

FORD:
1998-2001 EXPLORER

MERCURY:
1998-2001 MOUNTAINEER

ISSUE

Some vehicles equipped with the 4.0L Single Overhead Cam (SOHC) engine may exhibit a Rattle/Buzz sound from under the vehicle. The noise may come from either the front or rear of the vehicle and may be present during idle and/or in all driving modes.

ACTION

Refer to TSB 02-08-01 (Primary Timing Chain Noise between 2000-3000 RPM under acceleration/load), TSB 98-21-01 (Exhaust Y-Pipe Vibration/Moan at Idle), TSB 98-20-10 (Heat Shield Rattle) for possible sources of noise. If the noise is still present, refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual pinpoint tests HF7-HF12, appropriate sections of the Workshop Manual, and the Service Procedure below to rule out exhaust leaks or restrictions. If after referencing the suggested TSB's and following the Service Procedure below there are no leaks or restrictions detected, the noise is the normal result of exhaust gasses passing through the inlet cones of the catalyst and no repair is required.

NOTE
UNLESS THE DIAGNOSIS INDICATES A FAILED CATALYST, DO NOT REPLACE THE CATALYTIC CONVERTER.

SERVICE PROCEDURE

Diagnostic Procedures: Catalyst Noise, Vibration, Rattling, Buzz

1. Inspect the exhaust system for loose components such as heat shields, hangers, etc. and tighten as required.

2. Check exhaust system for misalignment and align as required.

3. Check for bent or damaged hangers and correct as required.

4. Check for any loose components such as throttle control cables. Noise caused by loose cables contacting the intake manifold can travel to the exhaust system and be misinterpreted as a catalyst rattle.

Diagnostic Procedures: Exhaust Leakage

1. Inspect the exhaust system for small areas of soot accumulation on the outside of pipes, mufflers, etc. Soot deposits often form at the site of an exhaust leak. If leakage exists repair as required.

NOTE
MUFFLERS AND RESONATORS OFTEN HAVE DRAIN HOLES TO REMOVE EXHAUST CONDENSATE. THIS ARE REQUIRED FOR EXTENDED COMPONENT LIFE.

2. Check all exhaust gaskets for evidence of leakage and repair as required.

Diagnostic Procedures: Exhaust Restriction

1. Inspect the exhaust system for obvious kinks or restrictions and correct as required.

2. Perform diagnostic procedures as outlined in the PC/ED Manual, pinpoint tests HF7-HF12 to determine if catalyst is plugged/restricted.

OTHER APPLICABLE ARTICLES: NONE

WARRANTY STATUS: INFORMATION ONLY





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