How to Change Thermostat Radiator Valves

Updated February 21, 2017

A vehicle's thermostat acts as a doorway between the radiator and the engine. Engines run at their most efficient when they run at normal operating temperature. When a cold engine is started, it is imperative that the engine be allowed to warm up as quickly as possible. For this reason, the thermostat operates to prevent the antifreeze from reaching the engine until the engine is warm. When the engine reaches a specified temperature, the thermostat opens, thereby allowing the antifreeze to circulate through the engine to cool it. A defective thermostat is either stuck in the open position, significantly delaying the engine's ability to warm up, or stuck in the closed position, resulting in an engine that quickly overheats. In either event, the thermostat must be replaced.

Ensure that the vehicle's engine is cool, since hot antifreeze poses a serious burn risk.

Remove the radiator cap by twisting the cap in a counterclockwise direction while simultaneously pressing down on the cap.

Drain the radiator by turning the radiator's drain plug with a wrench. The drain plug is typically located on the bottom portion of the radiator on the driver's side.

Remove the upper radiator hose. Remove the end that is attached to the radiator first. Remove the radiator hose by first loosening the hose clamp on the end of the radiator hose with a flathead screwdriver, then pulling the hose away from the radiator.

Trace the upper radiator hose to where the hose meets the engine. This is where the vehicle's thermostat is located. Remove this end of the radiator hose.

Remove the thermostat's housing. The housing is located on the engine and is the piece that the upper radiator hose lead to. To remove the housing, remove the housing's bolts with a wrench, then pull the housing away from the engine to expose the thermostat.

Remove the thermostat by simply lifting it out of the engine.

Ensure that the thermostat's housing, as well as the housing's mating surface on the engine, is free from old gasket deposits and other debris. If deposits are present, scrap them off both surfaces with the blade of a flathead screwdriver or a gasket scraper.

Insert the replacement thermostat into the engine.

Install the thermostat housing. Coat one side of a new thermostat housing gasket with gasket sealer, then place the coated side of the gasket against the thermostat's housing. Coat the other side of the gasket with gasket sealer, then place the thermostat housing over the thermostat. Secure the housing into place by inserting the housing's bolts through the housing into engine, then tightening each bolt with a wrench.

Install the upper radiator hose. Slide the hose over the thermostat housing, then secure the hose into place by tightening the screw on the hose clamp. Attach the other end of the radiator hose to the radiator in the same manner.

Close the radiator's drain plug at the bottom of the radiator by turning the plug in a clockwise direction with a wrench.

Fill the radiator with antifreeze.

Install the radiator cap by twisting the cap in a clockwise direction while simultaneously pressing down on the cap.

Allow at least 2 hours to pass to ensure that the gasket sealer has dried to complete the replacement.

Things You'll Need

  • Wrench
  • Flathead screwdriver
  • Gasket scraper
  • Gasket sealer
  • Antifreeze
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About the Author

John Stevens has been a writer for various websites since 2008. He holds an Associate of Science in administration of justice from Riverside Community College, a Bachelor of Arts in criminal justice from California State University, San Bernardino, and a Juris Doctor from Whittier Law School. Stevens is a lawyer and licensed real-estate broker.