Hummer H1 Service Manual page 189

4-6 Cooling System
ENGINE COOLING SYSTEM SERVICE
Depressurizing/Draining
WARNING: To avoid injury, do not remove surge tank
filler cap before depressurizing cooling system when
engine temperature is above 190°F (88°C).
1. If engine is hot, place a thick cloth over surge tank filler
cap. Turn counterclockwise to first stop to release internal
pressure (Figure 4-8).
2. After pressure has vented, remove cap.
3. Open drain valve and drain system (Figure 4-7).
4. Close drain valve.
Replenishing
NOTE: Ensure surge tank coolant level is 3/4 full before se-
curing filler cap.
1. Ensure drain valve is closed and heater control valve is
open (Figure 4-7).
2. Fill system with proper antifreeze solution (Table 4-1).
3. Install filler cap on surge tank (Figure 4-8).
4. Start engine and run at fast idle (1500 rpm) until engine
temperature reaches 190° F (88° C). Stop engine.
5. Depressurize system.
6. Fill with proper antifreeze solution until surge tank is 3/4
full (Table 4-1).
7. Install filler cap on surge tank (Figure 4-8).
8. Start engine and run at fast idle (1500 RPM) until engine
temperature reaches 190° F (88° C). Stop engine.
9. Depressurize system. Use tester to ensure proper coolant
protection is provided.
10. Install filler cap on surge tank.
11. Start engine and check cooling system for leaks.
10 O'CLOCK
POSITION
8 O'CLOCK
POSITION
Figure 4-6: Fan Shroud Clearance Check Points
____________________________________________________________
2 O'CLOCK
POSITION
FAN
SHROUD
4 O'CLOCK
POSITION
DRAIN VALVE
Figure 4-7: Drain Valve
SURGE TANK
FILLER CAP
Figure 4-8: Surge Tank and Filler Cap Location
Expected Ambient
Temperature
120° to -32° F
(49° to -36° C)
Table 4-1: Antifreeze Preparation Guide
SURGE
TANK
Antifreeze/
Water Mixture
50% antifreeze/
50% water
®