Reverse Flushing; Spin-On Coolant Filter - PREVOST H3-41 Maintenance Manual

4. Drain descaling solution from the cooling
system.
5. Refill with clean water and carefully rinse the
cooling system to completely evacuate all
remaining descaling solution.
6. On heavily contaminated system, reverse
flush the cooling system to prevent remaining
dirt and scale deposits from clogging the
radiator tubes or being forced through the
water pump (refer to paragraph 9.2 Reverse
Flushing below).
7. Flush the system.
8. Refill system with appropriate coolant.
9.2

REVERSE FLUSHING

After the engine and radiator have been
thoroughly de-scaled, they should be reverse-
flushed. The water pump should be removed
and the radiator and engine reverse-flushed
separately to prevent dirt and scale deposits
from clogging the radiator tubes or being forced
through the pump.
accomplished by hot water, under pressure,
being forced through the cooling system in a
direction opposite to the normal flow of coolant,
loosening and forcing deposits out.
The radiator is reverse flushed as follows:
1. Remove the radiator inlet and outlet hoses
and replace existing radiator cap with a new
one.
2. Attach a hose to the top of the radiator to
lead water away from the engine.
3. Attach a hose at the bottom of the radiator
and insert a flushing gun in the hose.
4. Connect the water hose of the gun to the
water outlet and the air hose to the
compressed air outlet.
5. Turn on the water and when the radiator is
full, turn on the air in short blasts, allowing
the radiator to fill between blasts.
NOTE
Apply air gradually. Do not exert more than
138 kPa (20 psi) air pressure. Too great a
pressure may rupture a radiator tube.
6. Continue flushing until only clean water is
expelled from the radiator.
The cylinder block and cylinder head water
passages are reverse flushed as follows:
Reverse flushing is
SECTION 05A: H3 SERIES COOLING SYSTEM
1. Remove the thermostats and the water
pump.
2. Attach a hose to the water inlet of oil cooler
housing to drain water away from engine.
3. Attach a hose to the water outlet at the top of
the cylinder head (thermostat housing) and
insert the flushing gun in the hose.
4. Turn on the water until the jackets are filled,
and then turn on the air in short blasts. Allow
jackets to fill with water between air blasts.
5. Continue flushing until the water from the
engine runs clean.
If scale deposits in the radiator cannot be
removed by chemical cleaners or reverse
flushing as outlined above, it may be necessary
to remove the upper tank and rod out the
individual radiator tubes with flat steel rods.
Circulate the water through the radiator core
from the bottom to the top during this operation.
10

SPIN-ON COOLANT FILTER

The optional engine cooling system filter is used
to filter out impurities such as scale or sand from
the coolant. The filter is mounted onto the
cooling fan drive mechanism aluminum casting
(Figure 17).
To replace a filter:
1. Close the filter shut-off valve on the filter
mounting head and unscrew the old filter
from mounting.
WARNING
Failure to relieve cooling system pressure
may result in personal injury.
2. Remove and discard the filter. Recover the
coolant remaining in the filter with a suitable
container.
3. Clean the filter adapter with a clean, lint-free
cloth.
4. Coat surface of gasket with clean antifreeze,
tighten 2/3 to 1 turn after gasket makes
contact with head.
5. Open the filter shut-off valve.
6. Start engine and check for leaks. After
shutdown, replenish fluid as necessary.
PA1621 Maintenance Manual All Series | January 2017 19