Radiator and Pressure Cap
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.
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.
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.
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
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.
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 water.
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.
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 it.
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.
large leaks or considerable damage is present, removal of the radiator for extensive
repair or replacement is usually required.