REMOVAL & INSTALLATION
NOTE: It is a good practice to check the operation of a new thermostat before it is installed in an engine. Place the thermostat in a pan of boiling water. If it does not open more than 1?4 in. (6mm), do not install it in the engine.
4.9L Engine
Fig. 1: Thermostat location - 4.9L engine
- Drain the cooling system below the level of the coolant outlet housing. Use the petcock valve at the bottom of the radiator to drain the system. It is not necessary to remove any of the hoses.
CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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.
- Remove the coolant outlet housing retaining bolts and slide the housing with the hose attached to one side.
- Remove the thermostat and gasket from the cylinder head and clean both mating surfaces.
- To install the thermostat, coat a new gasket with water resistant sealer and position it on the outlet of the engine. The gasket must be in place before the thermostat is installed.
- Install the thermostat with the bridge (opposite end of the spring) inside the elbow connection.
- Position the elbow connection onto the mounting surface of the outlet, so that the thermostat flange is resting on the gasket and install the retaining bolts. Tighten the bolts to 15 ft. lbs. (20 Nm).
- Fill the radiator and operate the engine until it reaches operating temperature. Check the coolant level and adjust if necessary.
5.0L, 5.8L and 7.5L Engine
Fig. 2: Unbolt the thermostat housing
Fig. 3: Pull away the thermostat from the housing
Fig. 4: Scrape the gasket material taking care not to gouge the aluminum mating surfaces
Fig. 5: Thermostat spring always faces down in all engines
Fig. 6: On gasoline engines, turn the thermostat CLOCKWISE to lock it into position on the flats in the outlet elbow
Fig. 7: Thermostat positioning
Fig. 8: Thermostat installation for the V8 engines
The gasoline-powered 5.0L and 5.8L engine thermostat is mounted vertically on the front of engine, the 7.5L engine thermostat is positioned vertically.
- Drain the cooling system below the level of the coolant outlet housing. Use the petcock valve at the bottom of the radiator to drain the system. It is not necessary to remove any of the hoses.
CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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.
- Disconnect the bypass hoses at the water pump and intake manifold.
- Remove the bypass tube.
- Remove the coolant outlet housing retaining bolts, bend the hose and lift the housing with the hose attached to one side.
- Remove the thermostat and gasket from the intake manifold and clean both mating surfaces.
To install:
- For 5.0L and 5.8L engines, coat a new gasket with water resistant sealer and position it on the outlet of the engine. The gasket must be in place before the thermostat is installed. Install the thermostat with the bridge (opposite end of the spring) inside the elbow connection and the thermostat flange positioned in the recess in the manifold.
- For the 7.5L engine, install the thermostat in the recess, then coat the gasket with a water resistant sealer and position the gasket on top of the thermostat.
- Position the elbow connection onto the mounting surface of the outlet. Tighten the bolts to 18 ft. lbs. (24 Nm) on the 5.0L and 5.8L engines; 28 ft. lbs. (38 Nm) on the 7.5L engine.
- Install the bypass tube and hoses.
- Fill the radiator and operate the engine until it reaches operating temperature. Check the coolant level and adjust if necessary.
6.9L and 7.3L Diesel Engines
NOTE: The diesel engine thermostat is on the front side of the intake manifold
1987-93 ENGINES
CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by 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.
WARNING The factory specified thermostat does not contain an internal bypass. On these engines, an internal bypass is located in the block. The use of any replacement thermostat other than that meeting the manufacturer's specifications will result in engine overheating! Use only thermostats meeting the specifications of Ford part number E5TZ-8575-C or Navistar International part number 1807945-C1.
- Disconnect both negative battery cables.
- Drain the coolant to a point below the thermostat housing.
- Remove the alternator and vacuum pump belt(s)
- Remove the alternator.
- Remove the vacuum pump and bracket.
- Remove all but the lowest vacuum pump/alternator mounting casting bolt.
- Loosen that lowest bolt and pivot the casting outboard of the engine.
- Remove the thermostat housing attaching bolts, bend the hose and lift the housing up and to one side.
- Remove the thermostat and gasket.
To install:
- Clean the thermostat housing and block surfaces thoroughly.
- Coat a new gasket with waterproof sealer and position the gasket on the manifold outlet opening.
- Install the thermostat in the manifold opening with the spring element end downward and the flange positioned in the recess in the manifold.
- Place the outlet housing into position and install the bolts. Tighten the bolts to 20 ft. lbs. (27 Nm).
- Reposition the casting.
- Install the vacuum pump and bracket.
- Install the alternator.
- Adjust the drive belt(s).
- Fill and bleed the cooling system.
- Connect both battery cables.
- Run the engine and check for leaks.
1994-96 ENGINES
- Disconnect both negative battery cables.
- Drain the coolant to a point below the thermostat housing.
- Remove the drive belt.
- Disconnect the upper radiator hose.
- Remove the thermostat housing, its O-ring and the thermostat.
To install:
- Install the thermostat and the thermostat housing O-ring in the hose connection.
- Place the outlet housing into position and install the screws. Tighten the screws to 15 ft. lbs. (20 Nm).
- Install the upper radiator hose.
- Install the drive belt.
- Fill and bleed the cooling system.
- Connect both battery cables.
- Run the engine and check for leaks.