How to Install the Thermostat on a 1981 Toyota Supra

It is common for the thermostat on your Toyota Supra to fail and become stuck in the open or closed position after years of service. This will adversely affect engine operation. If the thermostat remains open, the engine will not be able to reach operating temperature. If the unit remains closed, the engine will overheat, causing severe and costly damage. Fortunately, you can replace the bad thermostat on your Supra model using some simple tools.

Tools Used: Drain pan, Slip joint pliers, Ratchet, ratchet extension and socket, Plastic scraper, New O-ring seal for 22R-EC engine models, New thermostat gasket for all other engine models, Distilled water, Antifreeze

Install Thermostat

Remove the Thermostat

Place a drain pan under the radiator drain valve, open the valve and remove at least 2 quarts of coolant to bring the level below the thermostat housing. Then close the drain valve.

Locate the thermostat housing on your Toyota Supra model. Follow the upper radiator hose towards the engine. The hose is attached to the housing. If you have a 22R-EC engine model, you will see the housing attached to the side of the engine. All other models have the thermostat housings sitting on top of the engine.

Remove the clamp securing the upper radiator hose to the thermostat housing using a pair of slip joint pliers.

Detach the upper radiator hose from the thermostat housing by carefully twisting the hose right and left as you pull it off the housing fitting.

Remove the thermostat housing from the engine block using a ratchet, ratchet extension and socket.

Withdraw the thermostat from its seat on the engine block.

Clean the thermostat housing and engine block mating surfaces of any gasket material left on them using a plastic scraper to avoid damaging the surfaces. This applies to the 8R-C, 18R-C and 5M-GE engine models.

Install the Thermostat

Install new O-ring seal on the new thermostat if you have a 22R-EC engine model.

Set the new thermostat on the engine and make sure the thermostat spring points towards the engine.

Place a new thermostat gasket on the mating surface of the engine block if you have an 8R-C, 18R-C or 5M-GE engine model.

Install the thermostat housing on the engine block and start the two mounting bolts by hand to avoid damage to the threads. Then tighten the bolts using the ratchet, ratchet extension and socket.

Attach the upper radiator hose to the thermostat housing.

Secure the upper radiator hose to the thermostat housing with the clamp using the pair of slip joint pliers.

Add a 50/50 mixture of distilled water and antifreeze to the radiator and bring the level to about an inch below the radiator neck. Add coolant to the reservoir and bring the level between the Low and Full marks.

Start the engine and check for coolant leaks on the upper radiator hose at the thermostat housing.

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