Installing a new thermostat in your Mazda 6 can be done at home but is different from many cars. The thermostat on the Mazda 6 is not on top of the motor but rather on the lower left side of the engine. The housing is mounted behind the water pump, not on the intake manifold as with most other cars. The housing is attached using three bolts and requires draining the coolant completely before removing it. The thermostat is available at Mazda dealerships and most auto parts stores.
Remove the negative battery terminal from the battery before starting any work. Isolate the terminal so it can not make contact with the battery while you are working. Position a drain pan under the centre of the radiator and remove the drain plug from the radiator with a wrench.
Drain the coolant from the cooling system into a bucket or drain pan. Open the radiator cap to allow air into the system. This will allow the coolant to drain faster.
Remove the drive belt from the front of the engine. Use a socket and ratchet to turn the bolt on the front of the tensioner pulley clockwise to release the tension on the belt and then remove it.
Remove the washer tank located on the side of the engine with a wrench or socket and ratchet. The thermostat housing sits behind it and cannot be reached with it in place.
Remove the power steering pump from the side of the engine with a wrench. Set it aside and locate the three bolts on the thermostat housing. Remove the bolts and pull the housing and old gasket off the block. Remove the thermostat from the block.
Install the new thermostat into the hole in the block, making sure it is oriented the same way as the old one. Install a new gasket and position the housing back on the block. Insert the three mounting bolts and tighten them with a socket and ratchet.
Reinstall the power steering pump on the engine and tighten the bolts with a socket and ratchet or wrench. Replace the washer tank with the original bolts and again, tighten with your socket and ratchet or wrench.
Reinstall the drive belt on to the pulleys and turn the bolt on the tensioner pulley counterclockwise to tighten the belt. The tensioner will apply the proper amount of belt tension so no further adjustment is needed on the belt.
Reinstall the drain plug in the bottom of the radiator and tighten until firm with a wrench. Refill the cooling system with new coolant. The system will need to be bled following the manufacturers recommendations to remove all the air from the system.
Reinstall the negative battery terminal on the battery and tighten it with a wrench or socket and ratchet.