Any leaks which are found must be corrected and the system re-
When the bubbles cease, read the pressure gauge. The gauge
reading is the pressure relief of the cap and should be within
11. If the system holds pressure, remove the radiator cap to
specifications. If the pressure reading exceeds the specified limit,
release the pressure; then, reinstall the cap.
replace the radiator cap.
12. Remove the adapter from the manifold or cylinder head and
7. If bubbles continue and the pressure drops below 10 psi for
reinstall the temperature sending unit. Check coolant level
engines with a 13 psi system, or below 5 psi for a 7 psi
and replenish, if necessary, with the correct coolant solution.
system, the radiator cap is not holding pressure. Release
pressure and wash cap in clean water to dislodge any
foreign matter from the valves. Check the rubber sealing
It is good practice to test new thermostats before installing them
surface of the cap and also the cap sealing surface in the
in the engine.
radiator neck. Inspect the cam lock flanges on both sides of
Remove the thermostat and immerse it in boiling water. Replace
the filler neck for maximum cap engagement.
the thermostat if It does not open more than 1/4 inch.
8. Re-check the cooling system as outlined in Step 6. If the
If the problem being investigated is insufficient heat, the
cap still does not hold pressure, the cap is damaged and
thermostat should be checked for leakage. This may be done by
must be replaced. Recheck system after a new cap is
holding the thermostat up to a lighted background. Light leakage
installed to assure that the system will now hold pressure.
around the thermostat valve (thermostat at room temperature) is
9. If the bubbles in the water container cease and the radiator
unacceptable and the thermostat should be replaced. It is possible, on
cap is within pressure specifications, observe gauge reading
some thermostats, that a slight leakage of light at one or two locations
for approximately two minutes. Pressure should not drop
on the perimeter of the valve may be detected. This should be
during this time.
10. If pressure drops, check for leaks at engine to radiator
hoses, by-pass hose, thermostat housing gasket, etc.
Do not attempt to repair the thermostat. It should be replaced if it
is not operating properly. Check the thermostat before installing
it, following the procedure under Thermostat Testing.
The fan drive belt should be properly adjusted at all times. A
loose drive belt can cause Improper alternator, fan and water pump
operation. A belt that is too tight places a severe strain on the water
1. Drain the radiator so that the coolant level is below the
A properly tensioned drive belt minimizes noise and also prolongs
the service life of the belt. Therefore, it is recommended that a belt
2. Remove the water outlet housing retaining bolts. Bend the
tension gauge be used to check and adjust the belt tension. Any belt
radiator upper hose upward and remove the thermostat and
that has been operated for a minimum of 10 minutes is
considered a used belt, and when adjusted, it must be adjusted to
the used tension shown in the specifications.
1. Install the belt tension tool on the drive belt (Figure 1) and
check the tension.
1. Clean the water outlet housing gasket surfaces. Coat a new
2. If adjustment is necessary, loosen the alternator mounting
water outlet housing gasket with water-resistant sealer.
bolts and move the alternator adjusting arm bolts. Move the
Position the water outlet housing gasket to the head
alternator toward or away from the engine until the correct
tension is obtained. Remove the gauge.
2. Install the thermostat in the intake manifold opening with the
copper pellet or element toward the engine and the
thermostat flange positioned in the recess. If the thermostat
is Improperly installed, it will cause a retarded flow of
3. Position the water outlet housing against the head. Install
and torque the retaining bolts to specifications. Install the
water bypass line and tighten hose connections.
4. Fill and bleed the cooling system. Operate the engine until
normal operating temperature is reached: then check the
coolant level and check for leaks.
Various types of flushing equipment are available. If pressure
flushing is used, make sure the cylinder head bolts are properly
tightened to prevent possible water leakage into the cylinders.
FIG. 1 Belt tensioning
Always remove the thermostat prior to pressure flushing.
CLEANING AND INSPECTION
A pulsating or reversed direction of flushing water flow will
loosen sediment more quickly than a steady flow in the normal
To remove rust, sludge and other foreign material from the
direction of coolant flow.
cooling system. use either FoMoCo Regular Cooling System Cleanser
or in severe cases use Heavy Duty Cleanser. Removal of such
material restores cooling efficiency and avoids overheating.
In severe cases where cleaning solvents will not properly clean
the cooling system for efficient operation, it will be necessary to use
the pressure flushing method.