The fan belt should be checked every time a vehicle
comes in for preventive maintenance (PM) to make sure
it is in good condition. A fan belt that has become
frayed, or has separated plies, should be replaced.
Replacement of a defective belt is usually made by
loosening the alternator or generator mounting bolts.
With the mounting bolts loose, push the alternator or
generator closer to the engine. This action provides
enough slack in the belt so it can be removed and a new
one installed. After installing a new belt, adjust it to the
proper tension and tighten the mounting bolts.
Radiator and Pressure Cap
When overheating problems occur and the system
is not leaking, check the radiator and pressure cap. They
are common sources of overheating. The pressure cap
could have bad seals, allowing pressure loss. The
radiator may be clogged and not permitting adequate air
flow or coolant flow.
Bent fins should he straightened and the radiator
core checked for any obstructions tending to restrict the
airflow. Radiator air passages can be cleaned by
blowing them out with an air hose in the direction
opposite to the ordinary flow of air. Water can also be
used to soften obstructions before applying the air blast.
In any event, the cleaning gets rid of dirt, bugs, leaves,
straw, and other debris which otherwise would clog the
radiator and reduce its cooling efficiency. Sometimes
screens are used in front of the radiator core to reduce
this type of clogging.
The radiator can be checked for internal clogging
by removing the hose connections and draining the
coolant. Use a garden hose to introduce a stream of
water into the top of the radiator. If the flow is sluggish,
the radiator is partially clogged. Another way to check
for this condition is to feel the radiator with your hand.
The radiator should be warm at the bottom and hot at the
top, with the temperature uniformly increasing from
bottom to top. Any clogged sections will feel cool.
Be sure the engine is not running when
making this test to avoid injury from the fan.
When the use of cleaning compounds and reverse
flushing fails to relieve a clogged core, the radiator must
be removed for mechanical cleaning. This requires the
removal of upper and lower radiator tanks and rodding
out the accumulated rust and scale from the water
passages of the core.
The radiator pressure cap should also be checked
for condition and proper operation. If it is dirty, the cap
can be cleaned with soap and water, then rinsed. The
seating surface of the vacuum and pressure valves
should be smooth and undamaged The valves should
operate freely when pressed against their spring
pressure and should seal properly when closed.
During the vehicles preventive maintenance (PM)
inspection, the radiator should be checked for leaks,
particularly where the tanks are soldered to the core,
since vibration and pulsation from pressure can cause
fatigue of soldered joints or seams. Neglect of small
leaks may result in complete radiator failure, excessive
leakage, rust clogging, and overheating. Thus it is
extremely important to keep the radiator mounting
properly adjusted and tight at all times and to detect and
correct even the smallest leaks.
A leak usually reveals its presence by scale marks or
watermarks below the leak on the outside of the core.
Permanent antifreeze does not leak through spaces
where water cannot pass. The antifreeze leak is more
noticeable, since it does not evaporate as quickly as
Stop-leak compounds can be effective to stop small
leaks at least temporarily. Stop-leak compounds harden
upon contact with the air, thus sealing off any small
openings. The main problem is that they give the
mechanic a sense of false security. For example, stop
leak may prevent seepage at a hose connection through
the inner lining, but finally the hose will rot and burst,
losing coolant and overheating the engine.
Stop-leak compounds can lead to radiator clogging
if water tubes already contain deposits that act as a
strainer. If coolant level gets too low, some stop-leak
ingredients may harden in the upper radiator and block
Before using stop leak, check your service
manual. The compound must be compatible
with the antifreeze and the inhibitors and must
be installed correctly and in the right quantity.
When large leaks or considerable damage is
present, removal of the radiator for extensive repair or
replacement is usually required.
What type of cooling system is the simplest?
In a liquid-cooled system, what component acts
as a heat exchanger?