Flushing; Cooling System Descalers; Reverse Flushing - PREVOST H3-41 Maintenance Manual

NOTE
If for any reason, the coolant level drops below
the surge tank level probe, the Check Engine
warning light will illuminate.
5. Stop engine and allow cooling.
6. Open the two heater line shutoff valves,
check the coolant level in the surge tank, and
then add as required.
CAUTION
Never pour cold coolant into a hot engine.
The sudden change in temperature may crack
the cylinder head or block.
If the entire system has been drained, redo the
previous steps while maintaining the two heater
line shutoff valves in the "Open" position. With
engine running, activate the driver's and central
heating systems to permit coolant circulation.
Complete the procedure by bleeding the heater
cores as explained in Section 22, under
"Bleeding Heating System".

9. FLUSHING

If the cooling system is contaminated, flush the
cooling system as follows:
1. Drain the coolant from the engine.
2. Refill with clean water.
CAUTION
If the engine is hot, fill slowly to prevent rapid
cooling and distortion of the engine castings.
3. To thoroughly circulate the water, start and
run the engine for 15 minutes after the
thermostats have opened.
4. Fully drain system.
5. Refill with clean water and operate for 15
minutes after the thermostats have opened.
6. Stop engine and allow cooling.
7. Fully drain system.
Vehicles without coolant filters:
Fill with a 50/50-antifreeze/water solution
and add required inhibitors.
Vehicles with coolant filters:
PA1615 Maintenance Manual All Series
SECTION 05b: X3 SERIES COOLING SYSTEM
Fill with a 50/50-antifreeze/water solution.
Replace coolant filter as per the Lubrication
and Servicing Schedule in section 24 if
required.
Dispose of spent fluids in an environmentally
responsible manner according to regulations in
effect in your area.
COOLING SYSTEM
(approximation)
Includes heating system: 24 US gal (91 liters)

9.1 COOLING SYSTEM DESCALERS

If the engine overheats and the fan belt tension,
coolant level and thermostat operation have
been found to be satisfactory, it may be
necessary to de-scale and flush the entire
cooling system.
Remove scale formation by using a reputable
and safe de-scaling solvent. Immediately after
using the de-scaling solvent, neutralize with a
neutralizing agent. It is important that product
directions be thoroughly read and followed.
After using the solvent and neutralizer, fully drain
the system, and then reverse flush the engine
and radiator (see "Reverse Flushing" in this
section) before filling the system with coolant
solution.

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.
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Section 05b revised September 2016
CAPACITY
Reverse flushing is
17