Lesson 3
WARNING
EXHAUST GASES CONTAIN POISONOUS CARBON MONOXIDE
As you know, exhaust gases contain carbon monoxide, which is a deadly, poisonous gas. Carbon monoxide
is especially dangerous because it is colorless and odorless. The driver and passengers of a vehicle can inhale
a fatal dose of carbon monoxide without knowing it. Death can result from an improperly repaired or
defective exhaust system.
Also, the exhaust gas leaving the engine is very hot and contains corrosive substances. It can ruin flexible
hoses, insulation on wiring, and the paint on the vehicle--as well as start fires. In addition, the exhaust gas
leaves the engine under high pressure and creates a loud, undesirable noise.
The exhaust system must therefore direct the exhaust away from the operator's and passenger's
compartments and away from electrical wiring and other materials that the exhaust can damage. The system
must include a means of muffling the noise of the escaping gases.
EXHAUST SYSTEMS
A typical exhaust system consists of the exhaust manifold, exhaust pipe, muffler, tailpipe, and clamps.
Often, the exhaust and tailpipe are made up of several pieces, and the tailpipe may have several sections.
EXHAUST MANIFOLD
The exhaust manifold collects the burned gases expelled from the engine cylinders and directs them into the
exhaust pipe.
Manifolds may be made of cast iron or be assembled from steel tubing. Usually, flanges are made on the
manifold where it connects to the engine and to the exhaust pipe. The mating surfaces of the flanges are
machined to a smooth finish for an airtight seal against the engine and the exhaust pipe to prevent exhaust
gases from leaking. Sometimes metal-to-metal contact provides the seal, but most of the time asbestos
gaskets are used. Nuts made of brass are used to secure the manifold flanges because brass does not rust.
The extreme heat causes steel nuts to rust very rapidly and then they are hard to remove.
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