How to replace thermostat?

ENGINE COOLANT THERMOSTAT
DESCRIPTION
The thermostat on the 2.7L and 3.5L engines are located on the lower left side of engine, near the front (Fig. 7 ) and (Fig. 8 ). The thermostat on both engines are on the inlet side of the water pump. The thermostats have an air bleed located in the thermostat flange. The air bleed allows internal trapped air during cooling system filling to be released.
Fig. 7: Removing Bolts Of Thermostat And Housing - 2.7L
Courtesy of DAIMLERCHRYSLER CORP.
Fig. 8: Removing Bolts Of Thermostat And Housing - 3.5L Courtesy of DAIMLERCHRYSLER CORP.
OPERATION
The engine cooling thermostat is a wax pellet driven, reverse poppet type. The thermostat is located in the inlet side of the engine to provide fast warm up and to optimize a consistent temperature in the engine. The thermostat is designed to prevent leakage through it and to guarantee a minimum engine operating temperature of 82°C (180°F). They also automatically reach wide open at a temperature of approximately 95°C (203°F) so they do not restrict flow to the radiator as temperature of the coolant rises in hot weather to around 104°C (220°F). Above 102°C (215°F) the coolant temperature is controlled by the radiator, fan, and ambient temperature, not the thermostat.
DIAGNOSIS AND TESTING - ENGINE COOLANT THERMOSTAT
The thermostat is operated by a wax filled container (pellet) which is sealed so that when heated to a predetermined temperature, the wax expands enough to overcome the closing spring and water pump pressure, which forces the valve to open. Coolant leakage into the pellet will cause a thermostat to fail open. Do not attempt to free up a thermostat with a screwdriver.
The open too soon type failure mode is included in the on-board diagnosis. The check engine light will not be lit by an open too soon condition. If it has failed open, a DTC diagnostic trouble code will be set. Do not change a thermostat for lack of heat by gauge or heater performance, unless a code is present. Refer to SELF-DIAGNOSTICS for other probable causes. Failing shut is the normal long term mode of failure, and normally, only on high mileage vehicles. The temperature gauge will indicate this condition.
ENGINE COOLANT THERMOSTAT - 2.7L
REMOVAL
1. Disconnect negative cable from remote jumper terminal.
WARNING: DO NOT REMOVE PRESSURE CAP WITH THE SYSTEM HOT AND UNDER PRESSURE BECAUSE SERIOUS BURNS FROM COOLANT CAN OCCUR.
2. Drain cooling system. 3. Remove the engine oil dipstick and tube. To prevent coolant from entering engine, cover the dipstick tube opening in crankcase with a suitable plug. 4. Raise vehicle on hoist. 5. Support the engine and remove the left engine mount. Refer to appropriate ENGINE article.

6. Remove generator support strut. 7. Disconnect generator electrical connector. 8. Remove the transaxle dipstick tube bracket attaching bolt. 9. Remove the lower heater hose tube bracket bolt. 10. Remove the lower heater hose from thermostat housing. 11. Remove radiator lower hose from thermostat housing. 12. Remove thermostat housing bolts (Fig. 9 ). 13. Remove thermostat and housing.
Fig. 9: Removing Bolts Of Thermostat And Housing - 2.7L Courtesy of DAIMLERCHRYSLER CORP.
INSTALLATION
1. Clean gasket sealing surfaces.

NOTE: Install thermostat with the bleed valve located at the 12 o'clock position.
2. Install thermostat and gasket into the thermostat housing. 3. Install thermostat and housing to cylinder block. Tighten attaching bolts to 12 N.M (105 in. Lbs.) (Fig. 9 ). 4. Connect the heater return and radiator lower hoses to the thermostat housing. Install hose clamps. 5. Install the heater hose tube bracket bolt. 6. Install the transaxle dipstick tube bracket attaching bolt. 7. Install the generator support strut. 8. Connect the generator electrical connector. 9. Install the left engine mount. 10. Lower vehicle. 11. Inspect and replace dipstick O-ring as necessary. Install the engine oil dipstick and tube. 12. Refill cooling system. 13. Connect negative cable to remote jumper terminal.
ENGINE COOLANT THERMOSTAT - 3.5L
REMOVAL

tk49raceTip: slow overheating with a/c or with out at idle

WARNING: DO NOT REMOVE PRESSURE CAP WITH THE SYSTEM HOT AND UNDER PRESSURE BECAUSE SERIOUS BURNS FROM COOLANT CAN OCCUR.
1. Disconnect negative cable from remote jumper terminal. 2. Drain cooling system. 3. Raise vehicle on hoist. 4. Disconnect electrical connectors from engine oil and power steering pressure switches. 5. Disconnect radiator and heater hoses from thermostat housing. 6. Remove thermostat housing bolts (Fig. 10 ). 7. Remove housing, thermostat, and gasket.
Fig. 10: Installing Bolts Of Thermostat And Housing - 3.5L
NOTE: The OEM thermostat is staked in place at the factory. To ensure proper seating of replacement thermostat, carefully remove the bulged metal from the thermostat housing using a suitable hand held grinder. It is not necessary to restake the replacement thermostat into the thermostat housing.

INSTALLATION
1. Clean gasket sealing surfaces. 2. Install thermostat and gasket into thermostat housing. For ease of installation, install bolts in housing for thermostat and gasket retention. 3. Install thermostat and housing to cylinder block (Fig. 10 ). Tighten bolts to 12 N.M (105 in. Lbs.). 4. Connect heater and radiator hoses and install hose clamps. 5. Connect electrical connectors to engine oil and power steering pressure switches. 6. Lower vehicle and connect negative cable to remote jumper terminal. 7. Refill cooling system. 8. Connect negative cable to remote jumper terminal.