COOLING SYSTEM LEAK TEST
WARNING: THE WARNING WORDS “DO NOT OPEN
HOT” ON THE PRESSURE CAP IS A SAFETY PRE-
CAUTION. WHEN HOT, PRESSURE BUILDS UP IN
COOLING SYSTEM. TO PREVENT SCALDING OR
INJURY, THE PRESSURE CAP SHOULD NOT BE
REMOVED WHILE THE SYSTEM IS HOT OR UNDER
PRESSURE.
With engine not running, remove pressure cap and
wipe the filler neck sealing seat clean. The cooling
system should be full.
Attach the Cooling System Tester 7700 or equiva-
lent to the pressure bottle and apply 104 kPa (15 psi)
pressure. If the pressure drops more than 13.8 kPa
(2 psi) in 2 minutes, inspect all points for external
leaks.
All radiator and heater hoses should be shaken
while at 104 kPa (15 psi), since some leaks occur only
while driving due to engine movement.
If there are no external leaks, after the gauge dial
shows a drop in pressure, detach the tester. Start
engine and run until the thermostat opens, allowing
the coolant to expand. Reattach the cooling system
tester. If the needle on the dial fluctuates it indicates
a combustion leak, usually a head gasket leak.
Fig. 1 Temperature Gauge Indications
7 - 10 ENGINE ZB
ENGINE (Continued)
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