Ford Explorer Quiz
Powertrain

Diagnosis and Testing - Exhaust System

In this manual: Powertrain
General Information — 41Chassis — 173Powertrain — 250Electrical — 303Body and Paint — 331
~6min read
0102030405075N·mlb·ft
Tightening torque found on this page

Symptom Chart

Symptom Chart: Symptom Chart - Exhaust System

Verify the customer concern. Inspect the exhaust system components for obvious signs of damage or other mechanical concerns using the following chart.


Visual Inspection Chart - Mechanical


  • Exhaust pipe pinched or crushed
  • Damaged muffler
  • Broken or damaged exhaust hanger brackets
  • Damaged catalytic converter
  • Loose or damaged heat shields

Verify the exhaust system is installed correctly, with the clamps properly positioned and tightened to specification. If the condition is not visually obvious, determine the symptom. GO to the symptom chart below.


Symptom Chart


Condition Possible Sources Action
Vehicle has low power or no power - vehicle performance concern
  • Exhaust pipe pinched or crushed
  • Damaged catalytic converter
  • Loose obstruction in the exhaust
 REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Restricted exhaust (possible frozen condensation in the muffler) CHECK the drain holes for foreign material. PARK the vehicle indoors to thaw. CHECK the vehicle for normal operation. If the condition persists, REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Burning odor - usually occurs at idle, smoke may be present
  • Foreign objects in the exhaust system
  • Missing heat shields
 CHECK the exhaust system for foreign material or missing heat shields. REPAIR or REPLACE components as necessary.
Odor - described as a sulfur or rotten egg smell.
  • Catalytic Converter
  • Excessive sulfur content in the fuel
 A slight sulfur odor is sometimes noticed. This is normal for catalytic converters. The cause is the sulfur content of the gasoline used. ADVISE the customer that no repair is required.
  • Rich fuel conditions
  • Misfire conditions
 REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Visible rust on the exhaust pipe surface Catalytic converter/exhaust system Surface rust is typical for materials used in exhaust systems. Exposure to heat or road salt can cause surface rust. CHECK for perforations. If there are no perforations, the condition is normal.

Symptom Chart: Symptom Chart - NVH

Symptom Chart


Condition Possible Sources Action
Scraping, squeaking or buzzing noise - underbody Loose or damaged heat shield CHECK the exhaust system for loose or missing heat shields or foreign material trapped between the shields and exhaust system components. If the heat shields are loose, INSTALL worm-drive clamp 7L5Z-5A231-AA and tighten to 7 N·m. If the heat shields are missing or the rattle, buzz or noise persists, INSTALL a new heat shield or component as necessary.
Loose or damaged exhaust isolators ENSURE the exhaust isolators are installed correctly. CHECK the exhaust isolators for wear or damage. INSTALL new isolators as necessary.
Damaged exhaust isolator hanger bracket CHECK the exhaust system components for damage or broken hangers. INSTALL new components as necessary. CHECK for loose or damaged exhaust system hanger brackets or fasteners. TIGHTEN the bolts to specification or INSTALL new components as necessary.
Loose or damaged catalytic converter or muffler MOVE the exhaust system to simulate vehicle bounce, check for exhaust contact with the body when the exhaust system is moved. Using a rubber mallet, tap the exhaust components to duplicate the noise concern. Apply light pressure to the muffler, then the catalytic converter. DETERMINE whether there are loose or broken baffles in the muffler or a loose or broken element in the catalytic converter. REPAIR or REPLACE components as necessary.
Exhaust contacting the chassis CHECK for signs of exhaust component contact with the body. REPAIR or REPLACE components as necessary.
Humming or clanking noise - underbody Loose or damaged exhaust isolators CHECK the exhaust isolators for wear or damage. INSTALL new isolators as necessary.
Exhaust contacting the chassis CHECK for signs of exhaust component contact with the body. REPAIR or REPLACE components as necessary.
Whistling, booming, droning or ticking noise - noise changes as the engine warms up. Noises are often accompanied by exhaust gases. Exhaust system leak CHECK the entire exhaust system for leaks. CHECK for holes, loose or damaged clamps/hangers, gaskets, sensors or torn welds. CHECK the chassis for grayish-white or black exhaust soot, which indicates an exhaust gas leak at that point. To amplify a small leak, have an assistant hold a shop towel over the exhaust tailpipe outlet while listening for the leak. REPAIR or INSTALL new components as necessary.
Catalytic Converter MOVE the exhaust system to simulate vehicle bouncing, check for exhaust contact with the body when moving the exhaust system. Using a rubber mallet, tap on the exhaust components to duplicate the noise concern. Lightly press on the muffler and catalytic converter. DETERMINE if there are loose or broken baffles in the muffler or a loose or broken element in the catalytic converter. REPAIR or INSTALL new components as necessary.
The muffler/resonator drain hole is enlarged due to corrosion. CONFIRM that the drain holes are the source of the noise. INSTALL new components as necessary.
Hissing or whistling noise — high-frequency sound that does not affect vehicle operation. Exhaust system – exhaust gas flow through pipes CHECK the exhaust system for leaks. Using a rubber mallet, tap on the exhaust system components to duplicate the noise concern. Lightly tap on the muffler and catalytic converter. DETERMINE if there are loose or broken baffles in the muffler, or a loose or broken element in the catalytic converter. REPAIR or INSTALL new components as necessary.
Rattling noise — occurs when the exhaust system is hot, engine off. Catalytic converter/exhaust system Cooling ping is the result of the exhaust system expanding and contracting when heating and cooling. This is a normal condition.
Vibration — occurs at idle and low engine speeds. Also accompanied by a clanking or buzzing noise. Loose or damaged exhaust isolator. CHECK the exhaust isolators for wear or damage. INSTALL new isolators as necessary.
Loose or damaged exhaust isolator hanger brackets. CHECK the exhaust isolator hanger brackets for wear or damage. INSTALL or REPAIR as necessary.
Exhaust system grounded to chassis REPAIR or INSTALL new components as necessary.
Engine drumming noise — usually accompanied by vibration. Damaged or misaligned exhaust system. CHECK the exhaust system for loose or damaged hangers or isolators. REPAIR or INSTALL new components as necessary.
Spray noise — noise is louder when cold, decreases or disappears when the vehicle reaches operating temperature. Damaged or worn exhaust system CHECK the exhaust system for leaks or damage. REPAIR as necessary.
Knocking — from underneath the vehicle, worse during acceleration. Incorrect exhaust system CHECK the exhaust system for chassis clearance. CHECK the exhaust isolators for damage. REPAIR as necessary.
Engine vibration — felt when engine speed increases and decreases. Load on the exhaust isolators. REPAIR or INSTALL new components as necessary.
Drumming noise — occurs inside the vehicle at idle or at high idle speeds, when hot or cold. Very low-frequency drumming is highly dependent on engine speed. Exhaust system vibration excites body resonances, causing interior noise. REPAIR or INSTALL new components as necessary.

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