WD Catalog 2018

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Chapter 7 – Inspection & Maintenance
7-10 - -
B. Warm up engine – Next, let the engine warm up to normal
operating temperature and set both fan and temperature on high.
Feel both heater supply and return hoses. If there is a noticeable
difference in their temperature, it indicates a low flow of coolant
through the heater core (a partially closed or blocked heater control
valve). This could result in poor heating performance during cold
weather conditions.
HEATER CORE
FAN CLUTCH
WATER PUMP
CHECK WATER
VALVE FUNCTION
BLOWER
ASSEMBLY
DEFROSTER VENTS
HOT TEMPERATURE
CAB AIR DIRECTION
COOL
DEF
FAN
OFF
HEATER SYSTEM CONTROL PANEL
CLEAN RADIATOR
OF DEBRIS
RADIATOR HOSE
CHECK ALL HOSES
AND CONNECTIONS
FOR LEAKS, FRAYS,
AND WEAR
HEATER SYSTEM IN
CAB CONTROL
TEST PRESSURE
RADIATOR CAP
CHECK COOLANT
LEVEL AND
APPEARANCE
2. Inspect Other Functions
There are some things you can’t see or feel when you inspect the thermo-
stat, heater core, radiator pressure cap, electrical switch and control valve
functions. Some of these can be checked with the pressure and thermostat
testers as described in Chapter 6. Ahand pump pressure tester can also be
used to check for coolant leaks. This is done by using the pump to raise the
pressure inside the system above normal operating pressure to force
small suspected leaks to show up.
Heater/cooling electrical and valve component inspection is the same
as air conditioner inspection. The controls are operated to see if they
function correctly to maintain or vary cab temperature and air flow.
Preventive Maintenance Worksheet
Please feel free to modify or copy the worksheet in Figure 7-9. Actual vehicle
use, mileage, operating conditions and maintenance budget may influence
service frequency.
Figure 7-8
Heater/cooling system po-
tential problem areas and
checks are indicated in this
drawing.