Perkins 4.99 - Water Pump and Thermostat Procedures; Refitting Water Pump and Seals; Thermostat Procedures

COOLING SYSTEM-M.4
To Refit the Water Pump
1. Fit the backplate followed by the water pump to
the cylinder block, using new joints lightly coated
with suitable jointing compound.
2. Secure the water pump assembly to the cylinder
block with the four setscrews.
3. Refit the fan belt and adjust to the correct tension.
4. Refit the fan using new lockwashers.
Water Pump Seals
Where 'Ceramic counter face water pump seals are fitted,
if the
engine is run without coolant, even for a few
seconds,
the heat build-up between the carbon seal and
ceramic counter face is very rapid, resulting in the
cracking of the ceramic. This often creates the mis-
understanding that the cause of leakage is due to the
incorrect assembly of the sealing arrangement of the
water pump.
THERMOSTAT
To Remove the Thermostat
1. Drain the coolant from the radiator.
2. Remove the water hose from the engine water out-
let connection at the front of the cylinder head.
3. Remove the two nuts and washers securing the
outlet connection to the thermostat housing.
4. Remove the outlet connection and joint.
5. Lift ouLthe thermostat as shown in Fig. M.6.
To Test the Thermostat
1. Immerse the thermostat in a suitable container of
water and slowly heat. An accurate thermometer
should be available to check the temperature of
the water as it rises.
2. Note the temperature at which the valve in the
unit commences to open. This temperature should
M6
be as stamped on the unit by the manufacturers.
3. If the unit does not function properly then a re-
placement thermostat will be required, as no
adjustment of these units is possible.
Certain engine applications have an external bypass
which incorporates a thermostat with a bypass blanking
valve. This valve closes the bypass port as the thermo-
stat opens directing the coolant through the radiator.
(see Fig.
M.7). When replacing a thermostat, the cor-
rect type must be fitted. Failure to fit the correct
thermostat may result in the engine overheating.
To Replace the Thermostat
Replacing the thermostat is a reversal of the removal
procedure. A new joint should be fitted between the
thermostat housing and the water outlet connection.
When the radiator has been refilled with coolant, check
that no leaks are visible.
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M7
1. Thermostat
2. Thermostat Bypass Valve
3. Bypass
Outlet
4. Outlet to Radiator