blowing them out with an air hose in the direction
radiator slows circulation so that the suction of the
water pump creates a low-pressure pocket, which
opposite to the ordinary flow of air. Water can also be
permits the water to convert immediately to steam and
used to soften obstructions before applying the air
perhaps cause the engine coolant to boil over.
blast. In any event, the cleaning gets rid of dirt, bugs,
Therefore, all old, cracked, or spongy hoses should be
leaves, straw, and other debris that otherwise would
replaced as soon as the condition is discovered. The
clog the radiator and reduce its cooling efficiency.
lower radiator hose is particular suspect because it is on
Sometimes screens are used in front of radiator cores to
the vacuum side of the pump. When this hose becomes
prevent this type of clogging.
soft with age, it tends to collapse, with the result just
The radiator can be checked for internal clogging
described. You can check such hoses as well as others
by removing the hose connections and draining the
by squeezing them; if they are "mushy," they should be
radiator. Then, introduce a stream of water into the top
replaced. However, where spiral spring stiffeners are
from a garden hose and observe the flow coming out at
used to control the tendency to collapse, such a test will
the bottom. If the flow is sluggish, the radiator is
not work and the hose will need to be removed for
partially clogged. Another way to check for this
condition is to feel the radiator with your hand after the
engine has been operated for some time. The radiator
should be warm at the bottom and hot at the top, with
the temperature increasing uniformly from bottom to
Normally, the water pump requires little in the way
top. Any clogged sections will feel cool.
of maintenance in day-to-day operation. Nearly all
water pumps use sealed bearings, so that even
lubrication service has been eliminated. However,
where provided, the air vent at the top of the housing
To avoid injury from the fan, do not make this test
and the drain hole at the bottom should be checked to
while the engine is running.
make sure they are not plugged with grease or dirt.
Pumping failures are most often caused by a broken or
loose drive belt, which requires that the belt be
Where use of cleaning compounds and reverse
replaced or adjusted. Leaks, which are also quite
flushing fails to relieve a clogged core, the radiator
common, may sometimes be corrected by replacing the
must be removed for mechanical cleaning. This
pump gasket. However, after long service, the pump
requires the removal of upper and lower tanks and
may develop a leak around the shaft or become noisy
removing the accumulated rust and scale from the
due to worn bearings or other defects. It will then
water passages of the core.
require replacement or rebuilding. Pumping capacity
The radiator pressure cap should also be checked
can be reduced as a result of edge wear of impeller
for condition and proper operation. If it is dirty, the cap
blades and wear of the pump housing caused by
can be cleaned with soap and water and then rinsed.
abrasive action of sand or rust in the system.
The seating surfaces of the vacuum and pressure valves
Sometimes a pump may cease to circulate coolant
should be smooth and undamaged. The valves should
because of eroded impellers or vanes or a buildup of
operate freely when pressed against their spring
rust or mineral deposits on the impellers or vanes. The
pressures and should seal properly when closed. By
pump operation can be checked with the engine
using the pressure tester, you can quickly check the cap
running by squeezing the upper radiator hose to
for proper operation.
ascertain the presence of a pressure surge.
Whether a defective pump is replaced or rebuilt
depends on parts supply and cost. Repair kits are
All hoses and tubing should be checked frequently
sometimes available for rebuilding water pumps. In
for leakage and general condition. You can also correct
most cases, however, it is more economical to simply
the leakage by tightening or replacing the hose clamps.
replace the pump. In fact, there are some pumps for
Deteriorated hoses should be replaced to preclude
which repair kits are not made. In any event, the
future troubles. For example, hoses sometimes rot on
removal and installation procedures, as well as the
the inside, allowing tiny fragments to flow through the
rebuilding procedure (if applicable), will vary on
system and become lodged in the radiator, tending to
different pumps. Therefore, the applicable shop
manual must be consulted for the step-by-step
clog it and cause overheating. Any restriction in the