Exhaust System Introduction
An exhaust pipe is not simply a passage that directs exhaust gases toward the rear of a vehicle. Its shape and volume have a direct influence on the engine’s output characteristics since they determine the amount of back pressure that acts upon the combustion chambers. Consequently, the engine’s performance can suffer if exhaust gases leak from the exhaust pipe (leaks can be caused by damage to the pipe or by defective joints) or if the flow of exhaust gases is hindered by corrosion or deformation in the pipe.
On vehicles exported to certain regions, a catalytic converter is incorporated in the exhaust system to minimize the carbon monoxide, hydrocarbons, and nitrogen oxides in the exhaust emissions. Any defect in the catalytic converter or in the exhaust line upstream of the catalytic converter can allow these toxic, environmentally harmful substances to escape into the atmosphere.
Exhaust noise is minimized by the muffler at the back of the exhaust pipe and by the submuffler that is fitted before the muffler. Any defect that allows exhaust gases to escape before passing through the sub-muffler and muffler can therefore cause excessive noise.
The exhaust system is attached to the body with floating mounts, which accommodate engine movement resulting from acceleration and deceleration. Any deformation or other defect that causes the exhaust pipe to touch the body directly can greatly increase the perceived levels of engine noise and vibration and can itself become a new source of noise.
Since the exhaust system becomes extremely hot during vehicle operation, heat shields are fitted between exhaust line components and the body. Any damage to these shields can cause the body to be damaged by exposure to high temperatures.
The shape of the exhaust system differs from one vehicle model to another. However, the inspection and replacement procedures are basically the same for all models.
Exhaust System Inspection
- Heat shield
- Muffler
- Exhaust pipe tips
- Heat shield
- Gasket Replace.
- Replace, Tighten the flange nuts in steps, alternating side-toside.
- Exhaust pipe B
- Heat shield
- TWC
- Gaskets Replace.
- Heat shield
- Mid pipe
- Replace, Tighten the flange nuts in steps,alternating side-to-side.
- Self-locking nut Replace.
- Self-locking nut Replace.
- Exhaust pipe A
- Gaskets Replace.
- Heated oxygen sensor (HO2S)
- Gaskets Replace.
- Self-locking nut Replace.
- Heat shield
- The exhaust system is extremely hot immediately after engine operation. Wait for its surfaces to cool down before starting work.
- Before entering the area below the vehicle, make sure the vehicle is supported securely. For maximum safety, wear a helmet while working.
1. Raise the vehicle.
2. Visually and physically check the exhaust system-to-body mountings as follows:
- Check for looseness in the mounting bolts and nuts.
- Check the rubber hangers for deterioration, wear, damage, and hardening.
- Check for looseness in the heat shield mounting bolts.
3. Check all joints in the exhaust system as follows:
- Check for looseness in the joint fasteners.
- Check for gaps in the joints.
On some vehicle models, special joints are used to accommodate movement of the engine relative to the exhaust system.
4. Inspect all parts of the exhaust system for rust, corrosion, and other defects as follows:
- Tap along the exhaust system with a hammer or other implement, starting at the engine end. Any portion that gives a dull sound when tapped is probably rusty or corroded on the inside, so it should be removed, inspected, and, if necessary, replaced. Portions with rust on the surface are probably corroded right through to the inside.
- Look particularly carefully for rust on flanges and for rust and cracks in welds.
- The three-way catalytic converter treats dense gases at extremely high temperatures, so it is prone to deterioration. Check it closely for signs of soot and tar leakage.
- Water may condense and collect in the bottom of the muffler during engine operation. Therefore, check the muffler for corrosion.
- Check all chassis mounting stays for rust and corrosion.
5. Lower the vehicle, then connect an extractor hose and fan to the exhaust pipe.
6. Start the engine, then raise the vehicle again.
7. Visually and physically check that all joints are free of exhaust gas leakage.
Exhaust System Replacement
- The exhaust system is extremely hot immediately after engine operation. Wait for its surfaces to cool down before starting work.
- Do not work alone; an assistant must be present to support the exhaust system and prevent it from dropping.
- Before entering the area below the vehicle, make sure the vehicle is supported securely. For maximum safety, wear a helmet while working.
Exhaust System Removal
Rust may have formed on the exhaust system’s mounting bolts and flanges during exposure to the heat of the engine’s exhaust gases. If any bolts or flanges are rusty, spray them with penetrating oil and wait a while before starting work.
- Loosen all the mounting bolts.
- Remove all parts of the exhaust system starting at the engine end.
- Remove the exhaust temperature sensor and oxygen sensor.
NOTE:
- If removal is performed from the muffler end, the weight of the exhaust pipe may cause deformation of the exhaust pipe-to-exhaust manifold joint or create abnormal curvature in the exhaust pipe.
- To avoid damaging the sensors, place them on a rag or other soft surface. Do not place them directly on the floor.
Exhaust System Installation
- Non-reusable parts must be replaced with new ones.
- Before reusing bolts and other items, make sure they are free of rust and other contamination.
- Tighten all nuts and bolts to their specified torques. Excessive tightening can damage gaskets.
- Loosely fit the exhaust system together, starting at the muffler end. First, join the pipe sections together, then attach the pipe sections to the vehicle. Fit sensors (if any) before attaching the pipe sections to the vehicle.
- When all parts are in place, tighten the fasteners to the specified torque. Tighten each fastener a little at a time, not in a single action.