Mazda Training manual — part 253

6 – COOLING SYSTEM

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Piston Engine Fundamentals

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REVIEW EXERCISE 9

Fill in the words that correctly complete these sentences. Check your answers with the
answer key on page 98.

1.

A radiator that has side tanks, rather than top and bottom tanks, is called a
______________________ radiator.

2.

A coolant fan that is driven by the engine is called a _______________________
drive.

Use the pressure cap illustration below to complete the following two items.

3.

Item

in this illustration is the ________________________.

4.

Item

in this illustration is the ________________________.

5.

Which of these symptoms would you expect to find in an engine that has a faulty
thermostat? More than one answer may be correct.

A. leaking oil

B. fan not rotating

C. overheating

D. noisy engine

6 – COOLING SYSTEM

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Answers to Review
Exercise 9

1. crossflow

2. mechanical

3. vacuum valve

4. radiator

reservoir

hose

5. C — over- heating

7 – GLOSSARY

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anti-drainback diaphragm

— an oil filter

component that keeps oil in the filter when
the engine is shut off.

BDC

— See bottom dead center.

bearing cap

— a U-shaped component

used to attach the crankshaft, connecting
rod, or camshaft to its support surface.

bearing clearance

— the gap between a

main bearing and a main journal.

belt and chain drive

— a camshaft drive

in which a timing belt drives the intake
camshaft, and a timing chain drives the
exhaust camshaft.

blow-off valve

— See pressure valve.

bore

—the diameter of a cylinder, usually

expressed in millimeters (mm).

bottom dead center

— the position of a

piston at its lowest point in the cylinder;
abbreviated as BDC.

bushing

— a circular, sleeve-type bearing.

bypass valve

— an oil filter component

that “senses” back-pressure from a clogged
filter and allows some oil to bypass the
filter.

cam follower

— See lifter.

cam lobe

— an off-center bulge on a

camshaft that pushes against a lifter or
rocker arm to control the opening and
closing of a valve.

cam-ground piston

— a piston that is

slightly oval shaped to allow for heat
expansion.

camshaft

— a solid or hollow cast iron

shaft with offset lobes, or cams, that control
the opening and closing of the valves.

camshaft flange

— a raised surface on

the camshaft that matches a thrust surface
in the cylinder head to control front-to-back
movement of the camshaft.

combustion

— the process of controlled

burning of an air-fuel mixture in the
cylinders.

combustion chambers

— the spaces in

the cylinder head where the air-fuel mixture
is compressed and burned.

compression ratio

— the ratio of the

cylinder volume at bottom dead center to
the volume at top dead center.

compression rings

— the top two rings

mounted on the piston that seal, scrape,
and cool the cylinder.

compression stroke

— the part of the

four-stroke cycle in which the upward
stroke of the piston compresses the air-
fuel mixture into a very small volume at the
top of the cylinder.

connecting rod

— attaches a piston to the

crankshaft; the connecting rod transfers the
movement of the piston to the connecting
rod journal on the crankshaft.

connecting rod bearing

— a split circular

sleeve that wraps around a connecting rod
journal on the crankshaft.

connecting rod journal

— a smooth

round surface, offset from the center line of
the crankshaft, that is used to attach the
connecting rods from the pistons; also
called a crankpin.

coolant passage

— a passage cast into

the cylinder block or cylinder head to carry
coolant around the cylinders.

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cooling system

— the engine components

that circulate coolant to maintain proper
operating temperatures in and around the
cylinders.

counterweight

— a weight cast into the

crankshaft opposite a connecting rod
journal; counterweights help balance the
crankshaft and prevent vibration during
high-speed rotation.

crankcase

— the chamber at the bottom of

the cylinder block where the crankshaft
turns.

crankpin

— See connecting rod journal.

crankshaft

— the shaft that changes the

up-and-down motion of the pistons into
rotational motion.

crossflow-type radiator

— a radiator with

side tanks that allow coolant to flow through
the core from side to side.

cylinder

— See cylinder bore.

cylinder block

— the main supporting

member of the engine that contains the
cylinders, pistons, connecting rods,
and crankshaft.

cylinder bore

— a machined space in the

cylinder block where the pistons are
housed.

cylinder head

— a structural member of

the engine that is bolted to the top of the
cylinder block; the cylinder head seals the
tops of the cylinders, and contains the valve
train components and spark plugs.

cylinder head gasket

— seals the

connection between the cylinder block and
cylinder head; the gasket is usually made
of steel coated with a softer material.

dipstick

— a fluid level gauge used to

measure the level of engine oil in the
oil pan.

displacement

—the volume of a cylinder

between the top dead center and bottom
dead center positions of the piston; the
displacement of an engine is the total
displacement of all the cylinders in the
engine, usually expressed in cubic
centimeters (cc) or liters (L).

distributor

— directs electrical current to

the spark plugs as they fire in turn.

distributor groove

— a groove on the

exhaust camshaft that drives the
distributor.

DOHC

— See dual overhead cam.

downflow-type radiator

— a radiator

with upper and lower tanks that allow
coolant to flow through the core from top
to bottom.

dual overhead cam

— an engine design

in which the valves and two camshafts are
mounted above the cylinders; one
camshaft operates the intake valves and
the other operates the exhaust valves;
abbreviated as DOHC.

electric fan drive

— a radiator fan drive

that uses an electric motor to operate the
fan only when a thermoswitch senses that
the coolant has reached a preset
temperature.

end play

— movement of the crankshaft or

camshaft from front to rear.