Inspect or Replace Thermostat

Coolant Thermostat General Information

IMPORTANT: Never operate engine without a thermostat installed. Without a thermostat installed, coolant will follow the path of least resistance through the bypass back to the water pump inlet causing engine to overheat.

Only replace thermostat with one of the same part number. Thermostats may look similar and can physically fit but are application specific. Installing the incorrect thermostat can cause engine to run too hot or too cold causing engine damage.

The thermostat controls the engine coolant temperature. When coolant temperature is below operating range, coolant is bypassed back to the water pump inlet. When coolant temperature reaches operating range, thermostat opens sealing off the bypass forcing coolant to flow to the radiator.

Removing Thermostat

1. 
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   A - Water Outlet Connection

   B - Cap Screws (3 Used)

   C - Thermostat

   Shut off engine and remove key.

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2. Allow engine to cool and relieve pressure in cooling system.

3. Drain engine coolant into an appropriate container until level is below upper water outlet connection (A).

4. Remove cap screws (B) and water outlet.

5. Lift thermostat (C) from engine block.

Inspecting Thermostat

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   Inspect thermostat for external damage such as cracks, embedded debris, missing check balls or a damaged seat.

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2. If no external damage is found, check for proper operation using the following procedure:

   1. Note nominal operating temperature stamped on the thermostat.

   2. NOTE: Be sure thermostat does not contact container during test.

      Hang thermostat and a proper thermometer in a container of water.

   3. Heat water and check temperature when thermostat begins to open and when it reaches fully open position. Replace thermostat if not within the following specifications.

      82° C (180 ° F) Nominal Temperature Thermostat
      	° C	° F
      Initial Opening Minimum	79	175
      Initial Opening Maximum	83	182
      Fully Opened	94	202
      88° C (190 ° F) Nominal Temperature Thermostat
      Initial Opening Minimum	86	186
      Initial Opening Maximum	89	193
      Fully Opened	97	207

Install Thermostat

1. IMPORTANT:

   
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   A - Water Outlet

   B - Cap Screws

   C - Thermostat

   Debris falling into thermostat opening when removing gasket or seal material can cause damage to cooling system and engine. Place a rag in the opening or use an old thermostat as a plug when removing old material.

   Only replace thermostat with one of the same part number. Thermostats may look similar and can physically fit but are application specific. Installing the incorrect thermostat can cause engine to run too hot or too cold causing engine damage.

   If a previously installed thermostat is being used, make sure to install a new seal.

   Clean the mating surfaces of the engine and water outlet using and abrasive pad and a clean cloth.

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2. Align thermostat (C) into housing.

3. Install water outlet (A) using previously removed cap screws (B). Tighten cap screws to specification.

   Item	Measurement	Specification
   Water Outlet Cap Screws	Torque	10 N·m 89 lb.-in.

4. Refill coolant.

5. Operate engine to remove air from cooling system and top off with coolant meeting proper specifications.