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How to Change the Thermostat in a Mitsubishi Eclipse

by Contributor

The Mitsubishi Eclipse is one of the most popular sport coupes in United States. Powerful engines, stylish design and comfort are the hallmarks of the Eclipse throughout its 15 years on the market. Mitsubishi then designed the Eclipse for the American market.

Step 1

Pull the negative cable from the battery. Drain the engine coolant into a sealable container.

Step 2

Note the position of the upper and lower radiator hose with a matchmark to facilitate reinstallation. Disconnect the lower hose on the 2.0L turbo and 2.4L engines. Pull the upper hose on the 2.0L non-turbo engine.

Step 3

Remove the retaining bolts and then take out the water outlet fitting. Take out the gasket from the thermostat and lift the thermostat off the engine. Clean all the mating surfaces to remove any old gasket material, dirt and debris.

Step 4

Position the new thermostat so that the jiggle valve is oriented straight up. Align the jiggle valve with the mark on the case.

Step 5

Install the water outlet fitting. Torque the retaining bolts on the 2.0L non-turbo engine to 16 foot pounds; 9.4 foot pounds on the 2.0L turbo and 2.4L engines.

Step 6

Put the radiator hose in as far as the projection of the water outlet fitting. Align the marks on the radiator hose and the clamp, then connect the radiator hose.

Refill the cooling system. Start the engine and test for leaks. Recheck the coolant level and add coolant as needed.


  • The hoses slide onto fittings or connectors that grip the individual hose and hold it in place with a clamp.
  • No special tools are required to remove or reconnect hoses. Label the hose and its connectors before separating.


  • Keep in mind that dogs and cats are attracted to and will drink coolant left in open containers or puddled on the floor. Ingestion is often fatal.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers
  • Replacement thermostat, new or rebuilt
  • New gasket for thermostat

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