With the thermostat cover separated you can see the thermostat.

Note its orientation. The old thermostat, pictured, was installed incorrectly. The arrow on the thermostat should be facing up/towards the rear of the car. This one was facing the driver's side.

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Driver's side

However, it was installed in the correct orientation at least. The side with the large spring should be facing in towards the engine.

Remove the old thermostat and the rubber gasket from the cover.