How do I replace the thermostat?

The first step will be to drain the coolant from the engine and radiator on a cold engine. The fastest way to do that is to remove the lower radiator hose. Drain the coolant out into a container. Then use a ratchet to move the belt tensioner and remove the drive belt off the front of the engine. Then you need to remove the idler bracket assembly to get room enough to get at the thermostat housing bolts. With it out of the way remove the clamp to the hose and the small one that goes to the oil cooler. Then remove the thermostat and housing. Clean the sealing surface very well. Reverse the process to install the new housing and thermostat. Reverse the process and tension the belts as the diagram shows. Then refill the system with coolant. To do that pour the coolant into the radiator and reservoir. Fill it, then start the engine, now let it warm up and while it does step on the throttle and hold the engine at about 2400 RPMs for 10 seconds, then back to idle. Repeat that about 5 times. Check the coolant level and add if necessary so it is at the max/full level. Now shut it off and let it cool fully. Check that the level is now at the minimum level at least. While it cools it will pull coolant into the engine and you don't want it to pull air back in.