Block Heater; Thermostat - Jeep cherokee 2000 Service Manual

7 - 4 COOLING SYSTEM
DESCRIPTION AND OPERATION (Continued)

BLOCK HEATER

DESCRIPTION
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
An optional engine block heater is available for all
models. The heater is equipped with a power cord.
The cord is attached to an engine compartment com-
ponent with tie-straps. The heater warms the engine
providing easier engine starting and faster warm-up
in low temperatures. The heater is mounted in a core
hole of the engine cylinder block (in place of a freeze
plug) with the heating element immersed in engine
coolant.
BLOCK HEATER SPECIFICATIONS
• 2.5L 4-Cylinder Engine: 115 Volts 400 Watts
• 4.0L 6-Cylinder Engine: 120 Volts 600 Watts
Fig. 6 Engine Block Heater
1 – BLOCK HEATER
2 – CYLINDER BLOCK
3 – BLOCK HEATER POWER CORD
OPERATION
Connecting the power cord to a grounded 110-120
volt AC electrical outlet with a grounded, three-wire
extension cord activates the block heater.

THERMOSTAT

DESCRIPTION
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
A pellet-type thermostat controls the operating
temperature of the engine by controlling the amount
of coolant flow to the radiator. On all engines the
thermostat is closed below 195°F (90°C). Above this
temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warm-up and overall
temperature control.
An arrow plus the word UP is stamped on the
front flange next to the air bleed. The words TO
RAD are stamped on one arm of the thermostat.
They indicate the proper installed position.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: A 'check engine' light and a DTC
will eventually be set, longer engine warm-up time,
unreliable warm-up performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
Fig. 7 Thermostat and Housing
1 – LONG BOLT
2 – GASKET
3 – THERMOSTAT
4 – THERMOSTAT HOUSING
5 – SHORT BOLT
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