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Cooling System
FAQ's
ANSWER:
An inoperative electric cooling fan motor. ( See Cooling
fan ), thermostat not opening, defective fan clutch ( RWD vehicles ),
coolant leaks, bad water pump, a bad head gasket or cracked cylinder head
( See Head
gasket ) and a restricted exhaust.
A thermostat regulates the engines temperature ( usually between
190-197 degrees F. ) and is generally located where the upper radiator
hose meets the engine. If the thermostat fails to open no coolant can
circulate from the engine to be cooled by the radiator.
A thermostat can fail mechanically or will not open properly if there is
an air pocket below it caused by a coolant leak or improperly filling and
bleeding the cooling system.
A fan clutch is belt drive fan that engages with engine RPM or engine
temperature to improve fuel economy. The fan clutch is engaged only when
needed and free spins the rest of the time. It is filled with a silicon
fluid that lubricates the clutch, if this fluid leaks out ( Oily streaks
radiating outward on the clutch. ) the clutch will no longer engage
properly and the engine will overheat.
Coolant leaks can be external or internal. External leaks can be found by
looking over the engine for traces of anti-freeze. Sometimes they can be
hard to locate if they are small and the anti-freeze evaporates before
leaving a trail anywhere. Internal coolant leaks cannot be seem because
the coolant is leaking inside the engine. The coolant is usually ends up
in the engine oil or is being burned by the engine because it is leaking
into the cylinders.
A bad water pump could be leaking, which can be hard to determine on newer
vehicles because they are located inside the timing belt cover, or not be
pumping anymore. The water pump has an impeller on the inside of the
shaft, this is what pumps the coolant. On some newer vehicles the impeller
is made out of a type of plastic and overheating the engine one time can
cause it to melt or fall off, but there is usually an underlying problem.
With steel and aluminum impellers they can fall off due to wear and age or
be corroded away by lack of maintenance. ( See Anti-freeze
)
In some cases the engine may overheat if the exhaust is restricted causing
excessive backpressure. You would most likely have other problems first,
like a drop in fuel economy, hard starting and poor performance. A
restriction in the exhaust is usually a plugged catalytic converter.
