How to Change the Thermostat on Cars

by Contributing Writer; Updated June 12, 2017

The Saturn car is a fuel-efficient car produced by General Motors. The high revolution engine in this car makes the coolant system a crucial part of the vehicle. The coolant system is controlled by a thermostat, which is set to open once the engine gets hot. At this point, the thermostat will release enough coolant to flow through the engine and cool it down. Once the thermostat starts to stick, it will need to be replaced. Draining the radiator will be required to prevent spilling the coolant during the replacement process.

Under The Hood:

 How to Change the Thermostat on GMC Sierra

Changing the Thermostat

Remove the thermostat from the engine by following the upper radiator hose to where it meets the thermostat housing. The thermostat housing is where the opposite end of the upper radiator hose mounts to the engine.

Drain enough coolant from radiator until it is below thermostat. Failure to do this will result in your antifreeze leaking out onto the ground.

Loosen clamp and remove radiator hose from thermostat housing. Some antifreeze will leak out: have some rags available. If your engine is a 4.8L, 5.3L, or 6.0L, remove the air inlet duct first.

Remove the bolts holding the thermostat housing on and pull the housing from the engine. The gasket might make it a little difficult, so do not be afraid to pull hard, but do not strike it with any tools as you can crack it.

Remove old thermostat and note its alignment.

Place a rag in the thermostat’s mounting hole so no gasket material can enter the engine and then scrape the gasket from the housing and the engine. Install the new thermostat in same position as old one.

Apply a sealant to the thermostat housing, the part you removed, and then the gasket as well.

Reinstall the housing and tighten down bolts snugly. Torque them with your torque wrench. If your engine is one of the following then toque them to 21 ft lbs: 4.3L, 5.0L, or 5.7L. If your engine is a 7.4L then torque the bolts to 27ft lbs. If your engine is a 4.8L, 5.3L, or 6.0L then torque the bolts to 11 ft lbs. Make sure you do not over tighten them.

Reinstall the radiator hose to thermostat housing and tighten the clamp.

Refill the radiator with coolant and start the engine, allowing it to reach normal operating temperature.

Check for any leaks at hose connection and thermostat housing. You can tighten them as necessary to stop any leaks.

Stop the engine and allow it to cool down completely then check the coolant level. Add coolant as required.

Items you will need

  • sockets

  • torque wrench

  • new thermostat and gasket

  • gasket scrapper

  • antifreeze

  • screwdriver

 How to Change the Thermostat in a Saturn Ion

Remove the Thermostat

Pull the negative battery cable from the terminal. Drain the engine coolant (see Warnings). Remove the bolts that hold the exhaust heat shield and then remove it.

Raise the vehicle on a lift or secure supports. Release the coolant from the water pump drain plug. Collect the coolant into a suitable container.

Loosen and remove the bolts that secure the thermostat housing. Lift off the thermostat housing and discard the O-seal.

Take the water pipe from the water pump assembly, then remove the water pipe seals and throw them away.

Remove the inner thermostat sleeve. Lift out the thermostat assembly.

Install the Thermostat

Position the thermostat cartridge into the housing. Align the cartridge tangs with the housing bolt holes to assure easy installation into the inner sleeve. Line up the notch on the inner sleeve and insert the sleeve into the housing.

Put a new O-seal on the water pipe. Use a bit of silicon gel to lubricate the seals as needed. Set the water pipe into the water pump assembly.

Fit the water feed O-seal by pushing it toward the water pump while twisting it gently so as not to damage or tear the O-ring.

Place the thermostat housing cover on the water pipe. Set the new thermostat housing cover seal into the recess groove.

Set the thermostat housing cover in place. Install the bolts to the cover and torque them to 89 inch pounds.

Lower the vehicle. Install the exhaust heat shield and bolt it in place. Torque the bolts to 17 foot pounds. Make sure to close the radiator drain valve and the water pump drain.

Fill the engine with coolant. Attach the negative battery cable. Start the engine and test for leaks.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change the Thermostat on a Hyundai Elantra

Begin by sliding under the front of the car and locating the radiator drain plug on the bottom of the passenger's side of the radiator. Slide the catch container under the drain plug. Use the socket set to loosen and remove the plug. Allow all the coolant to drain out of the system.

Follow the coolant line that comes out of the bottom of the radiator and enters the engine block. Where the line enters the block, there is a small oval cover. Use the socket set to remove the two screws holding this oval cover on. Below the cover, you will find the thermostat.

Pull the thermostat out and then slide in the new thermostat. Replace the cover and tighten down the mounting screws. Unscrew the radiator cap and fill the system with a 50/50 mix of water and radiator fluid. Start the car and see if it cools down like it should.

Items you will need

  • Socket set

  • New thermostat

  • Coolant

  • Liquid catch container

 How to Change the Thermostat in a Mazda 6

Disconnect the battery ground cable. Drain the coolant from the system and store it in an appropriate container. Take out the drive belt.

Leave the pipe connected to the power steering pump and remove the pump with the pipe as a single unit. Push the power steering oil pump out of the way.

Take the water hose and the lower radiator hose from the thermostat. Remove the thermostat fasteners.

Lift out the thermostat housing, the thermostat and the gasket. Remove the gasket and discard it.

Install a new gasket to the thermostat and then set the thermostat in place. Set the thermostat housing in position and torque the fasteners to 71 to 101 inch pounds.

Fill the cooling system with the appropriate type and mix of coolant. Recycle the coolant when possible.

Reconnect the battery ground cable. Start the engine and test for coolant leaks.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Replace a Thermostat on a Polaris ATV

Locate the main coolant hose and follow it to the thermostat housing on the engine block, after allowing the engine to cool down completely.

Place a clean drain pan or bucket under the thermostat housing to catch any coolant that leaks out during the replacement.

Loosen the clamp that attaches the main coolant hose to the thermostat coupling with a screwdriver, then remove the hose. Make sure any spilled coolant goes into the drain pan.

Remove the two bolts holding the thermostat housing to the engine block with a socket wrench.

Note the position of the thermostat and pull it out of the opening.

Remove the old gasket from around the opening. Scrape off any that is stuck to the surface, making sure no pieces go into the opening.

Place the new gasket over the opening.

Insert the new thermostat into the opening. Make sure it is in the same position as the old thermostat. If the thermostat comes with a bell-like valve opening, make sure the opening is to the top.

Replace the thermostat housing, bolts and coolant hose.

Pour any spilled coolant back into the radiator or overflow reservoir.

Start the engine and check for leaking coolant.

Items you will need

  • Thermostat

  • Gasket

  • Phillips screwdriver

  • Socket wrench

 How to Change the Thermostat in a Hyundai Sonata

Allow the engine to cool completely before servicing the vehicle. Disconnect the negative battery cable. Drain the coolant in the radiator to a level that is below the thermostat.

Remove the coolant outlet fitting and its gasket. Discard the gasket. Clean any dirt or gasket material from the outlet fitting.

Lift out the thermostat, noting its orientation. Install the new thermostat in the same position as the old one. Replace the coolant outlet fitting with a new gasket.

Fill the cooling system with the appropriate type and amount of coolant. Reconnect the negative battery cable.

Start the engine and allow it to run until it is warm. Check for leaks and proper operation. Check the level of the coolant in the overflow tank and add coolant as necessary.

 How to Replace a Thermostat in a Saturn SL1

Draining the Radiator

Open the hood to access the coolant system. Twist the coolant reservoir cap off counterclockwise. Remove it and set it aside.

Set the parking brake to prevent the car from rolling backwards when raised. Chock the back wheels.

Place a jack under the front cross-member. Raise the front of the car high enough to place jack stands under the pinch points located under the front doors. Lower the car onto the jack stands.

Unbolt the splash guard at the bottom of the car with a socket wrench.

Place a drain pan under the radiator. Locate the drain plug at the bottom of the radiator on the passenger side. Turn the drain plug counterclockwise with a pair of pliers and drain the coolant. Tighten the plug back onto the radiator once the coolant has drained. Pull the drain pan out from under the car.

Tighten the splash guard back onto the bottom of the car with the socket wrench. Do not over-tighten the bolts as they are made of a hard plastic and could strip out.

Raise the car up and remove the jack stands. Lower the car to the ground with the jack.

Replacing the Thermostat

Locate the thermostat by tracing the lower radiator hose to the engine. This can be reached easier from the top of the engine compartment.

Unscrew the two bolts at the end of the radiator hose with a socket wrench. Pull the hose and the thermostat away from the engine.

Loosen the hose from the thermostat housing with a flat head screwdriver. Pull the thermostat housing out of the hose.

Place the new thermostat and housing into the hose. Tighten the hose clamp to secure it in place.

Apply RTV silicone around the ridge in the housing. Place a new O-ring onto the silicone. The silicone will hold the O-ring in place for mounting the thermostat housing.

Push the housing back together. Screw the two bolts into the bolt holes to secure the housing. Tighten the bolts with the socket wrench.

Pour pre-mixed coolant into the reservoir.

Start the car and let it idle. Once the car warms up, pour coolant into the reservoir until the level is full. Tighten the cap onto the reservoir.

Close the hood and turn off the car.

Items you will need

  • Jack

  • Jack stands

  • Pliers

  • Drain pan

  • Socket set

  • Socket wrench

  • Replacement thermostat

  • Replacement O-ring

  • 2 gallons of coolant

  • RTV silicone

 How to Change a Thermostat in a Jaguar

Raise your Jaguar off the ground with a jack and secure it on jack stands.

Place a bucket under the radiator and either open the drain plug or loosen and disconnect the coolant hose to allow the coolant to drain into the bucket. Disconnect the coolant hose with a flat head screwdriver by loosening the hose clamp.

Locate the thermostat housing by following one of the two large hoses at the top or bottom of the radiator that connects to the engine housing. If the piece that the hose connects to is one solid component and not bolted onto the engine, you will need to follow the other hose instead. The thermostat housing is secured to the engine block by three or four bolts.

Use a ratchet and socket set to loosen and remove the thermostat housing bolts. You may need to move or remove other components in the engine compartment to reach the bolts.

Lift the thermostat housing off of the engine block to access the thermostat. Note how the thermostat is positioned as you will need to install the new thermostat in the same position.

Remove the thermostat from its mount and discard it.

Scrape the remains of the thermostat gasket from the bottom of the thermostat housing and from the thermostat mount on the engine block, then scrub both clean with a scouring pad.

Apply a layer of gasket sealant to the bottom of the thermostat housing then press the thermostat gasket into the layer.

Place the new thermostat into its mounting area and replace the thermostat housing over it. Secure the housing with the bolts, then replace all the engine components you may have moved or removed.

Refill the radiator with coolant then lower the Jaguar off the jack stands with the jack.

Items you will need

  • Ratchet and socket set

  • Replacement thermostat

  • Flat head screwdriver

  • Gasket sealant

  • Jack

  • Jack stands

  • Bucket

  • Razor blade

  • Scouring pad

 How to Replace the Thermostat in an Audi A4

Raise the front end of your Audi A4 by driving up on a set of car ramps and placing your vehicle in park.

Place a 4-by-4 inch wood block behind one of the rear tires to keep the vehicle from rolling backward.

Use a socket wrench to remove the pan that covers the bottom of the engine.

Locate the red plastic cap that was behind the pan that you just removed. This red cap is your radiator drain plug. Remove the radiator cap from the top of the radiator and then place a drain pan under the red drain plug and turn it with a pair of pliers to allow the coolant to drain completely from the radiator. Once the coolant has completely drained, turn the drain plug to close it off. Be careful when using the pliers on the drain plug that you do not snap the plug off.

Slide under the vehicle and locate the thermostat housing that is sitting just above the oil pan drain plug. Pour the drained coolant from the drain pan into an empty plastic container and label the container so that you do not reuse the expelled coolant. Place the empty drain pan under the thermostat housing before you attempt to remove the housing to allow the coolant from the engine to drain into it.

Remove the 10 mm bolts that hold the thermostat housing on the engine block with a metric socket wrench. Do not lay directly underneath the thermostat housing as the coolant from the engine will begin to drain as soon as you loosen the bolts on the housing. Keep a towel or cloth with you to clean off any spilled coolant .

Remove the thermostat housing from the engine and lift the old thermostat out of the housing. Use a piece of emery cloth to clean the face of the thermostat housing and the engine block where the housing is mounted from any remaining gasket material or debris.

Spread a layer of gasket seal around the face of the thermostat housing and place the new thermostat on the housing, with the thermostat spring facing out from the housing. Position the housing back on the engine block and secure it to the block with the bolts.

Replace the pan the sits across the bottom of the engine of your Audi A4 and then refill the radiator with coolant and put the radiator cap back on the radiator. Remove the wood block from the back tire of your vehicle. Turn the engine on and drive the Audi A4 off of the car ramps. Allow the engine to run at idle for a few minutes to verify that the thermostat is working properly and then shut the engine off.

Items you will need

  • Car ramps

  • 4-by-4 inch wood block

  • Metric socket wrench set

  • Socket extension

  • Pliers

  • Drain pan

  • Empty plastic container

  • Black marker

  • Towel

  • Emery cloth

  • Gasket seal

 How to Change the Thermostat in a Mercury Villager

Disconnect the negative battery cable from the terminal. Drain the cooling system so that the level of coolant is below the level of the thermostat.

Remove the thermostat housing and set it aside. Lift out the thermostat.

Set the new thermostat in position. Make sure the jiggle valve is in the upright position. Replace the thermostat housing.

Refill the cooling system with the appropriate type and amount of coolant. Replace the radiator cap securely.

Reconnect the negative battery cable to the terminal. Start the engine and allow it to run for several minutes to warm up. Check for proper operation.

 How to Change the Thermostat in a Subaru Forester

Removing the Thermostat

Open the hood and place a drain pan under the radiator drain valve.

Remove the radiator cap.

Open the radiator valve and let the coolant from the radiator drain.

Close the radiator valve once the coolant has finished draining.

Raise the front of the vehicle using a floor jack and safely support it on two jack stands.

Remove the engine under cover using a wrench or ratchet and socket.

Disconnect the lower radiator hose from the thermostat housing on the engine side using a pair of rib joint pliers, Phillips screwdriver or ratchet and socket, depending on type of clamp used on your particular model.

Unscrew the two thermostat housing mounting bolts using a ratchet and socket.

Remove the thermostat housing and thermostat unit from the vehicle.

Installing the Thermostat

Clean the thermostat housing and engine mating surfaces using a soft brush to avoid damaging the surfaces.

Set the new thermostat in place along with a new rubber ring. Make sure the thermostat spring points towards the engine and the jiggle pin faces upward.

Install the thermostat housing and start the two mounting bolts by hand to avoid damage to the threads.

Tighten the bolts using a ratchet and socket.

Install the lower radiator hose on the thermostat housing and tighten the clamp using a pair of rib joint pliers, Phillips screwdriver or ratchet and socket, depending on type of clamp used on your particular model.

Replace the engine under cover using a ratchet and socket.

Lower the vehicle.

Refill the cooling system with 50 percent water and 50 percent new anti-freeze. Pour the coolant through the radiator neck using a funnel if necessary.

Replace the radiator cap.

Refill the coolant reservoir with coolant, bringing the level between the Low and Full marks.

Start the engine and let it idle for about three minutes to bring the engine to operating temperature.

Check the coolant reservoir level and add if necessary to bring the level between the Low and Full marks.

Turn off the engine.

Items you will need

  • Drain pan

  • Floor jack

  • 2 jack stands

  • Soft brush

  • New thermostat rubber ring

  • New anti-freeze

  • Funnel

 How to Change the Thermostat in a Subaru Outback

Raise the vehicle and remove the engine undercover. Drain the cooling system (see Warnings).

Loosen the clamp and take the lower radiator hose from the thermostat cover. Take off the thermostat cover and the gasket. Lift the thermostat off the engine.

Clean the thermostat mating surfaces to remove gasket material, dirt and debris. Set the thermostat on the intake manifold. Orient the thermostat with the jiggle pin positioned upward on the 2.2L and 2.5L engines.

Install the thermostat cover and a new gasket. Connect the lower radiator hose to the thermostat cover. Tighten the clamp.

Replace the engine undercover and tighten the fasteners. Lower the vehicle.

Refill the cooling system with the proper amount and mix of coolant. Start the engine and check for leaks. Make the necessary adjustments.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change a Thermostat on a Cadillac DeVille

Remove the thermostat housing by removing the two bolts that hold it onto the DeVille's engine, then lift the thermostat housing off the engine to expose the thermostat. In the DeVille thermostat replacement, the radiator hose is still connected to the housing. Drain the hose onto a clean bucket, then push the hose and the housing off to the side so you can access the thermostat.

Pull the thermostat out of the DeVille's intake. It is not bolted into place; remove it by pulling up on it. It may stick if it's been in there for years, but pulling on it should break it loose. Pull the old gasket off the intake and wipe the machined surface off with a clean towel. Make sure every bit of the old gasket is removed; if necessary, scrape bits off with a putty knife or blade. Don't let any of the bits get into the intake.

Place the new thermostat into the intake manifold and place a new thermostat gasket on top of the manifold

Place the thermostat housing on top of the gasket and bolt both pieces back into place.

Replace the excess radiator fluid back into the radiator thorough the filler cap.

Items you will need

  • Cadillac DeVille thermostat

  • Cadillac DeVille thermostat gasket

  • Bucket

  • Wrench

  • Clean towel

 How to Change the Thermostat in a Mitsubishi Eclipse

Pull the negative cable from the battery. Drain the engine coolant into a sealable container.

Note the position of the upper and lower radiator hose with a matchmark to facilitate reinstallation. Disconnect the lower hose on the 2.0L turbo and 2.4L engines. Pull the upper hose on the 2.0L non-turbo engine.

Remove the retaining bolts and then take out the water outlet fitting. Take out the gasket from the thermostat and lift the thermostat off the engine. Clean all the mating surfaces to remove any old gasket material, dirt and debris.

Position the new thermostat so that the jiggle valve is oriented straight up. Align the jiggle valve with the mark on the case.

Install the water outlet fitting. Torque the retaining bolts on the 2.0L non-turbo engine to 16 foot pounds; 9.4 foot pounds on the 2.0L turbo and 2.4L engines.

Put the radiator hose in as far as the projection of the water outlet fitting. Align the marks on the radiator hose and the clamp, then connect the radiator hose.

Refill the cooling system. Start the engine and test for leaks. Recheck the coolant level and add coolant as needed.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change the Thermostat in a 2002 Oldsmobile Silhouette Mini Van

Remove the tension band clamp from the radiator hose by squeezing the tension tabs together with a pair of pliers. With the tension released, pull the hose off the housing. A small amount of fluid could drain from the hose. To minimize this, hold the hose vertical to drain the fluid back into the Radiator.

Remove the three bolts that secure the housing to the engine with a socket and a ratchet. Pull upward on the housing to remove it from the engine.

Pull the old thermostat O-ring gasket out of the mating surface of the thermostat housing and replace it with a new one.

Pull the old thermostat out of the engine. Take note of the its orientation. The end with the spring rests inside the engine. Place the new thermostat into the engine in the same manner.

Place the thermostat housing over the thermostat and secure it by tightening the three bolts.

Push the radiator hose back onto the thermostat housing and secure it with the tension clamp.

Items you will need

  • Pliers

  • Socket set

  • Thermostat O-Ring

  • Thermostat

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.