Thermostat Operation; Thermostat Replacement; Checking Thermostat; Coolant - PREVOST H3-41 Maintenance Manual

4

THERMOSTAT OPERATION

4.1

THERMOSTAT REPLACEMENT

1. Drain the cooling system.
2. Remove the bolts, the thermostat housing
and the thermostat. Carefully clean the
thermostat seat and all cylinder head-to-
thermostat housing mating surfaces.
FIGURE 13: VOLVO D13 THERMOSTAT HOUSING
3. Install the new thermostat. Make sure that the
rubber seal remains properly seated.
4. Position the thermostat housing to the
cylinder head, install and tighten the bolts.
TORQUE: 15-21 lb-ft (20-28 Nm)
5. Install the rubber radiator hose to the
thermostat housing. Position the clamp and
tighten to secure.
6. Fill the system with the recommended

coolant.

7. Start the engine, check for leaks and proper
operation. After shutdown, replenish fluids as
necessary.
4.2

CHECKING THERMOSTAT

A function check must be carried out before
installing a new thermostat.
NOTE
Check to be sure that the thermostat closes
fully. This can be done by holding it up to the
light to check that there is no visible gap at the
opening point. If the thermostat does not close
properly, replace it.
1. Warm up water in a receptacle to 75°C
(167°F) and immerse the thermostat in the
water. Use a piece of wire attached to the
thermostat.
PA1615 Maintenance Manual All Series | Section 05a revised September 2016
SECTION 05a: H3 SERIES COOLING SYSTEM
2. After at least 30 seconds, check that the
thermostat is still closed.
3. Now warm the water to 100°C (212°F). After
at least 30 seconds at the boiling point,
check that the thermostat has opened at
least 7mm (9/32in). If the thermostat has not
opened, it must be replaced. A good
thermostat starts to close at 95°C (203°F)
and is fully closed at approximately 85°C
(185°F).
5 COOLANT
5.1

COOLANT LEVEL VERIFICATION

Coolant level is correct when coolant reaches
the middle of the surge tank sight glass when
cold (ambient temperature). Fill the tank as
necessary with the same 50/50 water-antifreeze
mixture normally used. Do not mix two different
types of coolant.
FIGURE 14: SURGE TANK IN ENGINE COMPARTMENT
WARNING
Hot engine coolant is under high pressure.
Allow engine to cool down before adding
coolant.
5.2

COOLANT LEVEL SENSOR

This warning device consists of a fluid level
probe mounted on the surge tank. The probe
sends a signal to the engine control module to
indicate coolant level. If the coolant level drops
below the probe, the "Check Engine" light
flashes and a diagnostic code is registered (see
section 01" ENGINE").
05114_3
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