Jeep 1997 Grand Cherokee Service Manual page 250

COOLANT TEMPERATURE SENSOR
7 - 22 COOLING SYSTEM
SERVICE PROCEDURES (Continued)
Fig. 21 Drain Plug—4.0L 6-CylinderEngine
Fig. 22 Drain Plugs—5.2/5.9L V-8 Engines
(1) With engine cold, slowly remove the radiator
cap. Raise vehicle on a hoist and locate radiator
draincock.
• 4.0L Engine: Radiator draincock is located on
the right/lower side of radiator facing to rear of vehi-
cle.
• 5.2/5.9L Engines: Radiator draincock is located
on the left/lower side of radiator facing to rear of
vehicle.
(2) Attach one end of a hose to the draincock. Put
the other end into a clean container.
(3) Open draincock and drain desired amount of
coolant from radiator.
REFILLING COOLING SYSTEM
(1) Tighten the radiator draincock and the cylinder
block drain plug(s) (if removed).
BLOCK DRAIN PLUG
BLOCK DRAIN
PLUG
(2) Fill system using a 50/50 mixture of ethylene-
glycol anifreeze and low mineral conent water. Fill
radiator to top and install radiator cap. Add suffi-
cient coolant to the reserve/overflow tank to raise
level to FULL mark.
(3) With heater control unit in the HEAT position,
operate engine with radiator cap in place.
(4) After engine has reached normal operating
temperature, shut engine off and allow it to cool.
When engine is cooling down, coolant will be drawn
into the radiator from the reserve/overflow tank.
(5) Add coolant to reserve/overflow tank as neces-
sary. Only add coolant to the reserve/overflow
tank when the engine is cold. Coolant level in a
warm engine will be higher due to thermal
expansion. To purge the cooling system of all air,
this heat up/cool down cycle (adding coolant to cold
engine) must be performed three times. Add neces-
sary coolant to raise tank level to the FULL mark
after each cool down period.
COOLING SYSTEM CLEANING/REVERSE FLUSHING
CAUTION: The cooling system normally operates
at 97 to 124 kPa (14 to 18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
CLEANING
Drain cooling system and refill with water. Run
engine with radiator cap installed until upper radia-
tor hose is hot. Stop engine and drain water from
system. If water is dirty, fill system with water, run
engine and drain system. Repeat until water drains
clean.
REVERSE FLUSHING
Reverse flushing of the cooling system is the forc-
ing of water through the cooling system. This is done
using air pressure in the opposite direction of normal
coolant flow. It is usually only necessary with very
dirty systems with evidence of partial plugging.
REVERSE FLUSHING RADIATOR
Disconnect the radiator hoses from the radiator fit-
tings. Attach a section of radiator hose to the radia-
tor bottom outlet fitting and insert the flushing gun.
Connect a water supply hose and air supply hose to
the flushing gun.
CAUTION: The cooling system normally operates
at 97 to 124 kPa (14 to 18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
Allow the radiator to fill with water. When radiator
is filled, apply air in short blasts allowing radiator to
refill between blasts. Continue this reverse flushing
until clean water flows out through rear of radiator
ZG