B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 008-013   Coolant Thermostat

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

• Drain the coolant. Refer to Procedure 008-018.

WARNING  Batteries can emit explosive gases. To avoid personal injury, always ventilate the compartment before servicing the batteries. To avoid arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

• Disconnect the negative (-) battery cable.
• Remove the drive belt.
• Disconnect the upper radiator hose. Refer to Procedure 008-045.

Remove the alternator mounting capscrew, loosen the alternator link capscrew, and lower the alternator.

Refer to Procedure 013-001.

Remove three capscrews, the thermostat housing, lifting bracket, thermostat, and thermostat seal.

Clean the mating surfaces.

NOTE: Do not let any debris fall into the thermostat cavity when cleaning the gasket surfaces.

Inspect the thermostat for obvious damage, such as obstructions caused by debris, broken springs, or stuck or missing vent pins.

Make sure the thermostat is clean and free from corrosion.

Suspend the thermostat and a 100°C [212°F] thermometer in a container of well-mixed water.

NOTE: Do not allow the thermostat or thermometer to touch the side of the container.

Heat the water slowly so the wax element in the thermostat has sufficient time to react to the rising water temperature.

Check the thermostat as follows:

Thermostat Requirements:

• Starts to open within 1°C [34°F] of 82°C [180°F]
• Fully open within 1°C [34°F] of 93°C [199°F]
• A full-open clearance between the thermostat flow valve and flange.

Position the rubber seal as shown for reassembly.

Install the thermostat, thermostat seal, thermostat housing, gasket, lifting bracket, and three capscrews.

Install the alternator. Refer to Procedure 013-001.

Install the drive belt. Refer to Procedure 008-002.

NOTE: After the belt tensioner has been raised to remove/install the belt, check the torque of the tensioner capscrew.

CAUTION  Always vent the engine during filling to remove air from the coolant system, or overheating will result.

Fill the cooling system. Refer to Procedure 008-018. Operate the engine, and check for leaks.