The thermostat on the Mazda B2200 pickup truck is located at the top of the engine and needs to be replaced to prevent the coolant system from running hot. The thermostat will stick and cause the truck to overheat. The thermostat regulates the temperature and is set to open once the engine temperature gets too hot. The thermostat will close once the engine cools down. This will give the coolant a chance to dissipate the heat and repeat the cycle.
Open the bonnet to access the engine compartment. Place a drain pan under the radiator. Open the petcock valve at the bottom of the radiator with a crescent wrench to drain some of the coolant out of the radiator. Draining at least 2 quarts will be adequate. Tighten the petcock valve to secure the remaining amount of coolant in the radiator.
Follow the upper radiator hose to the side of the engine. Squeeze the hose clamp with a pair of pliers to loosen the clamp from the radiator hose. Pull the radiator hose off the thermostat inlet pipe.
Unbolt the thermostat housing with a socket wrench. The housing will separate and expose the head of the thermostat. Pull the thermostat out of the part of the housing still connected to the engine. The thermostat has a jiggle pin. Note that the pin is located towards the top of the thermostat.
Scrape the gasket material off the exterior of the thermostat housing with a razor scraper. Ensure there is no gasket material on the cover as well.
Slide the new gasket over the studs to secure it in place. The new gasket will prevent the thermostat housing from leaking coolant.
Deposit the new thermostat into the housing. Ensure the spring goes in first and the jiggle pin is on the top.
Bolt the housing back together with the socket wrench. Push the hose onto the housing inlet pipe.
Squeeze the hose clamp with the pliers. Slide the hose clamp over the inlet pipe and the hose, then release the hose clamp. The clamp will tighten the hose to the pipe.
Twist the radiator cap counterclockwise to pull it off the radiator. Start the truck and allow it to idle. Pour in coolant until it is visible at the neck of the radiator. Wait for the truck to warm up and pour in additional coolant until the radiator cannot hold any more coolant.
Tighten the radiator cap back onto the radiator. Turn the vehicle off.
Contact a local recycling centre to dispose of the coolant. Pour the coolant into a sealed container so there is no chance that animals and small children can get into it.