Coolant-Adding Additional - Jeep Wrangler 1999 Electronic Service Manual

TJ
DIAGNOSIS AND TESTING (Continued)
WARNING: IF VEHICLE HAS BEEN RUN RECENTLY,
WAIT AT LEAST 15 MINUTES BEFORE REMOVING
RADIATOR CAP. WITH A RAG, SQUEEZE RADIATOR
UPPER HOSE TO CHECK IF SYSTEM IS UNDER
PRESSURE. PLACE A RAG OVER THE CAP AND
WITHOUT PUSHING
COUNTER-CLOCKWISE
ALLOW FLUID TO ESCAPE THROUGH OVERFLOW
HOSE INTO COOLANT
TANK. SQUEEZE RADIATOR UPPER HOSE TO
DETERMINE WHEN
RELEASED. WHEN COOLANT AND STEAM STOP
BEING PUSHED INTO TANK AND SYSTEM PRES-
SURE DROPS, REMOVE RADIATOR CAP COM-
PLETELY.
RADIATOR CAP—PRESSURE TESTING
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install the cap on pressure tester (tool 7700 or
an equivalent) (Fig. 14).
Fig. 14 Pressure Testing Radiator Pressure
Cap—Typical
Operate the tester pump and observe the gauge
pointer at its highest point. The cap release pressure
should be 83 to 124 kPa (12 to 18 psi). The cap is
satisfactory when the pressure holds steady. It is also
good if it holds pressure within the 83 to 124 kPa (12
to 18 psi) range for 30 seconds or more. If the pointer
drops quickly, replace the cap.
CAUTION: Radiator pressure testing tools are very
sensitive to small air leaks, which will not cause
DOWN, ROTATE
TO THE FIRST
RESERVE/OVERFLOW
PRESSURE HAS
cooling system problems. A pressure cap that does
not have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to tool. Turn tool upside
down and recheck pressure cap to confirm that cap
CAP needs replacement.
STOP.
INSPECTION
Visually inspect the pressure valve gasket on the
cap. Replace cap if the gasket is swollen, torn or
BEEN
worn. Inspect the area around radiator filler neck for
white deposits that indicate a leaking cap.
COOLANT—LOW LEVEL AERATION
If the coolant level in radiator drops below top of
radiator core tubes, air will enter cooling system.
Low coolant level can cause thermostat pellet to be
suspended in air instead of coolant. This will cause
thermostat to open later, which in turn causes higher
coolant temperature. Air trapped in cooling system
also reduces amount of coolant circulating in heater
core resulting in low heat output.
COOLING SYSTEM DEAERATION
As the engine operates, any air trapped in cooling
system gathers under the radiator cap. The next time
the engine is operated, thermal expansion of coolant
will push any trapped air past radiator cap into the
coolant reserve/overflow tank. Here it escapes to the
atmosphere into the tank. When the engine cools
down the coolant, it will be drawn from the reserve/
overflow tank into the radiator to replace any
removed air.
SERVICE PROCEDURES
COOLANT LEVEL—ROUTINE CHECK
NOTE: Do not remove radiator cap for routine
coolant level inspections. The coolant level can be
checked at coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining coolant level
without removing radiator pressure cap. With engine
idling and at normal operating temperature, observe
coolant level in reserve/overflow tank. The coolant
level should be between ADD and FULL marks.
COOLANT—ADDING ADDITIONAL
Do not remove radiator cap to add coolant to
system. When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene-glycol antifreeze containing
low mineral content water. Remove radiator cap only
COOLING SYSTEM 7 - 19