Thermostat

REMOVAL & INSTALLATION

NOTE: If the replacement thermostat is equipped with a jiggle pin, the pin must be install facing upwards toward the top of the engine (12 o'clock), and should be on the side facing the water outlet. When installing the thermostat gasket, the seal print side should face the cylinder head.

2.2L Engine

1. Drain enough coolant to bring the coolant level down below the thermostat housing. the thermostat housing is located on the left front side of the cylinder block.

   CAUTION
   When draining the coolant, keep in mind that cats and dogs are attracted by the ethelyne glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2. Disconnect the temperature sending unit wire.
3. Remove the coolant outlet elbow.
4. If so equipped, position the vacuum control valve out of the way. The vacuum control valve is not used on California trucks.
5. Disconnect the coolant by-pass hose from the thermostat housing.
6. Remove the thermostat and housing from the engine.
7. Note the position of the jiggle pin and remove the thermostat from the housing.
8. Remove all gasket material from the parts.

   Fig. 1: Thermostat installation

   To install:

9. Position the thermostat in the housing with the jiggle pin up. Coat a new gasket with sealer and install it on the thermostat housing.
10. Install the thermostat housing using a new gasket with water resistant sealer. Tighten the bolts to 14–19 ft. lbs. (19–25 Nm).
11. Install the coolant outlet elbow and vacuum control valve (if equipped).
12. Connect the by-pass and radiator hoses.
13. Connect the temperature sending unit wire.
14. Fill the cooling system with the proper coolant. Operate the engine and check the coolant lever. Check for leaks.

2.6L Engine

1987-88

The thermostat is located in a water box at the timing belt end of the intake manifold.

1. Drain the cooling system to a level below the thermostat.

   CAUTION
   When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2. Remove the hoses from the thermostat housing.
3. Remove the thermostat housing.
4. Remove the thermostat and discard the gasket. Clean the gasket surfaces thoroughly.

   To install:

5. Position the gasket on the water box. Center the thermostat in the water box and attached housing. Tighten the bolts to 15 ft. lbs. (20 Nm).
6. Connect the radiator hose to the thermostat housing. Tighten the hose clamp to 35 inch lbs. (4 Nm).
7. Fill the cooling system.

1989-93

The thermostat housing is at the end of the upper hose, on the cylinder head side, above the alternator.

1. Drain the cooling system to a point below the housing.

   CAUTION
   When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2. Remove the upper hose.
3. Remove the upper nut and lower bolt and remove the housing.
4. Remove the gasket and thermostat. Discard the gasket.
5. Thoroughly clean the mating surfaces of the head and housing.

   To install:

6. Position the new thermostat in the head with the jiggle pin on the upper side.
7. Coat the gasket with an adhesive sealer and stick it in place on the head.
8. Install the housing and tighten the nut and bolt to 19 ft. lbs. (26 Nm).
9. Fill the cooling system.

3.0L Engine

The thermostat housing is located at the engine end of the lower radiator hose.

1. Raise and support the front end on jackstands.
2. Drain the cooling system.

   Fig. 2: After moving the hose clamp away from the thermostat housing pipe, disconnect the lower radiator hose

   Fig. 3: Using a socket, remove the three thermostat housing mounting bolts

3. Remove the lower hose.
4. Unbolt and remove the housing and thermostat.

   NOTE: Some engines have a housing which incorporates an O-ring, eliminating the need for a gasket. On these engines, use no sealer when replacing the housing.On engines which incorporate a gasket, thoroughly clean the mating surfaces and use a new gasket coated with adhesive sealer.

   Fig. 4: After the mounting bolts are removed, remove the thermostat housing from the engine

   Fig. 5: Pull the thermostat down out of the opening in the engine

   Fig. 6: During assembly, make sure that the notch sticking out of the side of the housing is facing outward

5. Install a new thermostat in the housing and position the housing on the engine. Some housings are equipped with a location mark on the side, the mark should face the front of the engine when the housing is installed. Tighten the bolts to 19 ft. lbs. (26 Nm).
6. Install the lower hose.
7. Fill the cooling system.

4.0L Engine

1. Drain the cooling system.

   CAUTION
   When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2. Disconnect the battery ground.
3. Remove the air cleaner duct assembly.
4. Remove the upper radiator hose.
5. Remove the 3 thermostat housing attaching bolts.
6. Remove the thermostat housing. You may have to tap it loose with a plastic mallet or your hand.

   To install:

7. Clean all mating surfaces thoroughly. Don't use a sharp metal tool! The housing and engine are aluminum.
8. Make sure that the sealing ring is properly installed on the thermostat rim. Position the thermostat in the housing making sure that the air release valve is in the up (12 o'clock) position.
9. Coat the mating surfaces of the housing and engine with an adhesive type sealer. Position the new gasket on the housing and place the housing on the engine. Tighten the bolts to 7–10 ft. lbs. (9–14 Nm).