Exhaust System: Testing and Inspection

DIAGNOSIS AND TESTING

WARNING: THE NORMAL OPERATING TEMPERATURE OF THE EXHAUST SYSTEM IS VERY HIGH. NEVER ATTEMPT TO SERVICE ANY PART OF THE SYSTEM UNTIL IT HAS COOLED. EXHAUST GASES CONTAIN CARBON DIOXIDE WHICH CAN BE HARMFUL TO HEALTH AND ARE POTENTIALLY LETHAL. LEAKS MUST BE REPAIRED IMMEDIATELY. NEVER OPERATE THE ENGINE IN ENCLOSED AREAS.

External leaks in the exhaust system are often accompanied by noises and exhaust fumes, therefore a visual inspection usually detects the location of the leak. When checking for exhaust leakage or noise, inspect the entire system for burned-out holes, loose or corroded clamps, muffler or exhaust inlet pipe.

Examine the under body for greyish-white or black exhaust soot which indicates the exhaust leakage at that point.

The effect of a small leak can be magnified by holding a rag over the tailpipe outlet while listening to the leak.

If this is carried out, ensure that gases are not inhaled - see WARNING.

When testing for a rattle or vibration condition it is helpful to use a rubber mallet. Tap on the exhaust components to simulate the bouncing action of the exhaust while watching for exhaust-to-body / chassis contact.

Also look for loose and rusted flange connections, loose or damaged exhaust shields or clamp and loose or broken exhaust outlet pipe brackets.

*The first catalyst in the exhaust system on all six cylinder models is made from a metallic substrate. The first catalyst is the one that always melts if persistent miss-fire is maintained at medium to wide throttle openings. When catalysts melt, they collapse and disintegrate.

Note: It is not possible to determine a catalyst melt down, by measuring the pressure in the exhaust at the oxygen sensor tappings, as these are positioned after the first catalyst.

If there is a suspected melt down:

- Remove the oxygen sensor and look for metal deposits on the sensor tip.

- Remove the under floor assembly and check the inside of the down pipe for metal deposits.

- Position the the under floor assembly on its outlet and tap lightly with a hammer.

- Check if loose metal beads fall out.

- Remove the down pipe and visually inspect for signs of catalyst disintegration.

Note: Position a small light up the back of the catalyst and look through the inlet face. If the catalyst is OK, you should see a regular pattern of tubes.





Symptom Chart




Test A, Exhaust Leakage or Noise




Test B, Restriction in Exhaust Systems