Thermostat Replacement - Hummer H1 Service Manual

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THERMOSTAT REPLACEMENT

1. Drain engine coolant below level of water crossover.
2. Remove bolts attaching thermostat cover to crossover
housing.
3. Remove thermostat cover and gasket (Figure 4-22).
4. Remove both thermostats (Figure 4-23).
5. Position new thermostats
(Figure 4-24). Be sure thermostat seals are seated in
counterbores. Wax pellet end of each thermostat goes
toward engine.
6. Apply Permatex no. 2 to both sides of thermostat housing
gasket. If gasket is not used, apply 3/16 in. (5 mm) bead of
Loctite 599, or Permatex Ultra Copper, or Ultra Black to
cover or crossover mounting surface.
7. Install thermostat cover and tighten cover bolts securely.
8. Fill and bleed cooling system.
THERMOSTAT
HOUSING
TWIN
THERMOSTATS
Figure 4-22: Thermostat and Cover
Removal and Installation
THERMOSTAT
WAX PELLET
Figure 4-23: Turbo Diesel Thermostat
05745159
in crossover housing
WATER
CROSSOVER
GASKETS
SEAL
Cooling System
THERMOSTAT SEATS
WATER
AND COUNTER BORES
CROSSOVER
Figure 4-24: Thermostat Location in Crossover
WATER PUMP AND ADAPTER PLATE
Removal
1. Remove hood with aid of helper.
2. Drain engine coolant.
3. Discharge A/C system refrigerant with equipment set on
recovery mode.
4. Remove radiator, shroud, coolers, and A/C condenser as
assembly.
5. Loosen and remove serpentine drive belt.
6. Remove fan and fan clutch (Figure 4-25).
7. Disconnect hoses at water pump.
8. Remove water pump and backing plate attaching bolts/
studs and remove pump and plate as assembly
(Figure 4-26).
9. Remove water pump and gasket from plate (Figure 4-27).
10. Clean all gasket material and sealer from plate.
8-BLADE FAN
FAN CLUTCH
Figure 4-25: Fan and Clutch Mounting
4-13
SERPENTINE
DRIVE BELT