How to Change a Mitsubishi Thermostat

by Michael Ryan

The thermostat on your Mitsubishi is a device that controls the flow of coolant into the engine. When the car starts, the thermostat is closed, allowing the engine to warm up. As the engine gets near its operating temperature, the thermostat opens, letting coolant enter the engine and maintain the operating temperature. When a thermostat fails, it can happen in the open or closed position. If a thermostat fails while open, it will keep the engine from warming up properly, which can lower fuel economy. If a thermostat fails while closed, it will keep coolant from entering the engine, which eventually causes the engine to overheat.

Step 1

Loosen the upper radiator hose. This is the hose that connects to top of the radiator to the engine. Loosen the hose on the end that connects to the engine by using a flat-tip screwdriver to loosen the circular clamp.

Step 2

Remove the hose. Pull the upper radiator hose off the end that connects to the engine. Have a drain pan underneath the hose to catch any coolant that remains in the hose.

Step 3

Loosen the thermostat housing. Use your ratchet and socket set to loosen the bolts that hold your Mitsubishi's thermostat housing in place. The number of bolts and their locations vary based on your Mitsubishi model.

Step 4

Remove the thermostat housing. With the housing loose, pull it off of the engine.

Step 5

Remove and replace the thermostat. Pull the old thermostat out of the engine. Scrape the old gasket off of the thermostat housing and thermostat. Replace it with the new thermostat; be sure to align the new thermostat in the same orientation as the old one you removed.

Step 6

Insert the new gasket. Put a new gasket on the end of the thermostat housing that comes in contact with the thermostat. If necessary, you can use an adhesive to hold the gasket in place while fitting the thermostat housing.

Step 7

Fit the thermostat housing. Reconnect the housing to the top of your new thermostat. Secure it by re-tightening the bolts that you removed in Step 3.

Step 8

Re-attach the upper radiator hose. Put the upper radiator hose over the inlet on the thermostat housing. Tighten it using the the clamp you removed in Step 1.

Step 9

Top off the coolant. With the new thermostat, thermostat housing and upper radiator hose in place, use the coolant collected in the drain pan to top off the coolant overflow bottle once service is complete.

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