How to Replace a Thermostat in Toyota Cars

by Contributing Writer

The thermostat in a Toyota car regulates the amount of radiator fluid allowed to flow through the engine. Depending on the needs of the vehicle, the thermostat will allow or restrict the fluid. The thermostat is a mechanical part in the engine and not an electronic module. This means the thermostat can break or wear out. When this happens, the thermostat must be replaced. This may sound like a job for a mechanic, but it is absolutely possible to avoid the repair shop by completing the job yourself.

Under The Hood:

 How to Replace a Thermostat in a Toyota Echo

Place a drain pan under the petcock on the Echo's radiator and drain the contents of the radiator into the drain pan.

Place a second drain pan under the oil pan and drain the contents of the oil pan into the container.

Follow the lower radiator hose to the location where it connects to the water pump. The pump positions right behind the alternator.

Remove the oil filter with an oil filter wrench to gain access to the necessary bolts to remove the thermostat housing.

Disconnect the wiring harness from the inlet housing if equipped with one. The only engine that has one is the 7A-FE engine. If the housing has no harness, skip this step.

Disconnect the radiator hose from the inlet housing by squeezing the tabs on the clamp together with pliers and then pulling on the hose.

Remove the two bolts that secure the thermostat housing to the cylinder head with a socket. Pull the housing off the pump to expose the thermostat.

Pull the thermostat and gasket out of the head and wipe down the mating surfaces with a clean rag.

Place the new gasket onto the thermostat and then place the thermostat into the head with the spring side inside the head. Position the jiggle valve between the stud bolts of the thermostat housing.

Place the thermostat housing over the thermostat and bolt it back into place.

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

Reconnect the wiring harness to the water inlet if equipped.

Fill the engine with 4 qt. of motor oil

Drain the coolant back into the radiator.

Items you will need

  • Drain pans

  • Oil filter wrench

  • Socket set

  • Rag

  • 4 qt. of motor oil

  • Funnel

 How to Replace a Thermostat on a 1998 Toyota Camry

Locate the metal thermostat cover by tracing the radiator hose from the radiator to where the hose connects on the engine. Remove the cover by loosening the two bolts that hold it onto the intake manifold. Lift the thermostat housing off the engine and hold it vertically to drain the fluid back into the radiator. Push the hose and housing off to the side to gain access to the thermostat.

Pull the old thermostat out of the intake manifold and discard it. Place the new thermostat into the intake manifold. The thermostat is directional. The end marked, "up" sticks out of the intake manifold. This ensures the thermostat properly controls the temperature of the engine.

Lift the old thermostat gasket off the intake manifold and discard it. Wipe the surface of the intake manifold clean with a cotton towel and then place a new thermostat gasket onto the intake manifold.

Place the thermostat housing onto the thermostat gasket and bolt it back into place.

Items you will need

  • Wrench

  • Thermostat

  • Towel

  • Thermostat gasket

 How to Replace a Thermostat in a Toyota

Trace the top radiator hose to the intake manifold to locate the thermostat. The radiator hose is a band clamped to the housing that holds the thermostat. The location will differ, depending on the model of Toyota and the engine size you are repairing.

Disconnect the radiator hose from the thermostat housing by removing the band clamp that's around the radiator hose. Use a Phillips screwdriver. Once the band clamp is loosened, pull the hose off the thermostat housing.

Remove the two bolts that hold the thermostat housing to the intake manifold. Most thermostats are on the back of the engine and can be hard to get to with a wrench. Using a 12mm socket with an extender (often called a breaker bar) will make it easier to reach the bolts. Once the bolts are removed, lift the thermostat housing off the intake manifold.

Lift the thermostat out of the manifold. It is not bolted into place. Place a towel into the hole to block debris from getting inside the engine. Use a scraper and scrape the old thermostat housing gasket off the intake manifold. Clean all debris off the manifold and remove the towel.

Place the new thermostat into the intake manifold and place a new thermostat housing gasket in place. Bolt the housing back onto the manifold. Make sure the thermostat is placed back into the intake with the correct side up. This will ensure the thermostat works properly.

Items you will need

  • Thermostat gasket

  • Scraper

  • 12mm socket

  • Ratchet extender

  • Ratchet

  • Screwdriver

  • Cotton towel

 How to Replace a Thermostat in a Toyota Sienna

Allow the vehicle to cool for 2 to 5 hours prior to working on the radiator so that you don't burn yourself. Place the drain pan underneath the radiator and open the petcock at the base of the radiator to allow it to drain. Once it stops draining, tighten the petcock.

Unplug the engine coolant temperature sensors on the thermostat housing, which is in the center of the engine block, at the front by the radiator. Then unbolt the water inlet pipe from the water inlet on the engine block and pull it away from the block.

Unbolt the water inlet from the engine block using the 3/8-inch ratchet and socket. Pull it away and pull out the thermostat with it, as well as the thermostat gasket.

Set the replacement thermostat gasket, then the thermostat in the housing. There is a small valve on the thermostat called a jiggle valve. This must be pointing up toward the stud at the top of the water inlet to function correctly. Reinstall the water inlet using the ratchet.

Install a replacement O-ring--included with the thermostat kit--onto the water inlet pipe, then bolt the pipe to the water inlet using the ratchet.

Open the radiator cap and fill the radiator with the Toyota coolant. Once it's full, reinstall the cap.

Items you will need

  • Drain pan

  • Toyota coolant

  • Flat-head screwdriver

  • Pliers

  • Replacement thermostat kit

  • 3/8-inch ratchet and socket set

 How to Replace the Thermostat in a 1991 Toyota Previa

Follow the large hose at the top of the radiator, on the driver's side, down to the thermostat housing. The housing is located on this hose, just before it goes into the engine. Place the bucket on the ground under the thermostat housing.

Remove the two bolts that hold the housing together with the socket set. Coolant may leak out as you loosen the bolts so adjust the placement of the bucket to catch the coolant as it drains. Remove the thermostat, taking note of how it was positioned in the housing.

Remove the gasket from the housing. Use a flat head screwdriver to scrape the gasket off the housing if it is stuck. Remove all remnants of the gasket to prevent leaking.

Place the new thermostat into the housing so it points in the same direction the used thermostat was pointed. Spread the lubricant on the new gasket, and place it back in the housing.

Put the housing back together and tighten the two bolts. Start the car. Make sure no coolant is leaking from the housing. Fill the coolant reservoir up to the "full" line with a mixture that's half water and half coolant.

Items you will need

  • Thermostat with gasket

  • Socket set

  • Flat head screw driver

  • Gasket lubricant

  • Bucket

 How to Change the Thermostat in a 2003 Toyota Matrix

Pull the radiator hose off of the thermostat housing by releasing the radiator hose retaining clip with a screwdriver and then pull the hose off of the housing. Shove a towel into the radiator hose to prevent getting radiator fluid on the engine.

Remove the two bolts that hold the thermostat housing onto the intake of the 2003 Toyota Matrix. With the bolts removed, lift the thermostat housing off of the intake.

Pull the thermostat out of the intake and then remove the thermostat gasket. The thermostat gasket may stick to the intake. If this happens you must scrape the gasket off with a scraper. If you need to scrape the gasket off you can avoid getting anything into the intake by filling the hole inside of the intake with a shop towel.

Place the new gasket onto the intake manifold and then place the new thermostat into the intake.

Place the thermostat housing back on top of the thermostat gasket and bolt it back into place. If the bolts are over tightened it can crack the bolt tabs on the housing.

Place the radiator hose back onto the thermostat housing and secure it with the retaining clip.

Items you will need

  • 2003 Toyota Matrix thermostat

  • 2003 Toyota Matrix thermostat gasket

  • Wrench

  • Screwdriver

  • Towels

 How to Change the Thermostat in a Toyota Highlander

Drain the cooling system. Drain the coolant into a sealable container. Disconnect the battery ground.

Take the radiator outlet hose from the thermostat. Loosen the bolt and then move it to remove the water inlet pipe. Remove the bolts that secure the water inlet and remove it.

Lift out the thermostat. Pull the gasket and discard it. Clean the gasket mating surfaces thoroughly to remove any gasket debris, carbon deposits and dirt.

Set a new gasket on the thermostat. Set the thermostat in place, aligning the jiggle valve with the upper stud bolt. Place the thermostat into the water inlet housing.

Connect the water inlet. Torque the bolts to 71 inch pounds.

Lubricate a new O-ring with soapy water and then install it on the water inlet pipe. Set the inlet pipe bolt in place to secure the pipe to the cylinder head. Torque the bolt to 15 foot pounds. Connect the radiator outlet hose.

Fill the cooling system to proper levels with the appropriate coolant. Start the engine, check for leaks 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 do I Change the Thermostat on 2.7 Liter Toyota Tacoma?

Drive the Toyota Tacoma onto a set of ramps to lift the front of the vehicle off the ground. Block the rear tire with a wheel chuck for safety.

Remove the radiator cap from the top of the radiator to relieve pressure on the coolant system. Do not remove the cap if the engine is hot. Wait until the engine cools to prevent serious injury from steaming hot coolant mist.

Open the petcock located on the bottom left of the radiator and drain the coolant into a drainage pan. Close the petcock once the fluid drains from the Tacoma.

Trace the lower radiator hose to the location where the hose connects to the water pump. Remove the hose by squeezing the pressure tangs on the radiator clamp together. Pull the hose off the water inlet tube.

Remove the two bolts that secure the inlet tube to the water pump with a 12 mm socket. With the bolts removed, the inlet tube easily falls off the water pump. The thermostat, o-ring and gasket are inside of the water inlet tube.

Discard the thermostat, gasket and o-ring. Place the new o-ring inside of the water inlet tube.

Put the spring end of the thermostat into the water pump and then place the gasket around the thermostat. Hold the two in place with your fingers while you adjust the water inlet tube over them.

Secure everything onto the water pump with the two 12 mm bolts.

Reconnect the lower radiator hose by sliding the hose onto the inlet tube. Squeeze the pressure tangs on the clamp and slide it approximately 1 inch from the end of the hose and let go of the tangs.

Pour a 50/50 mix of antifreeze, also known as coolant, and distilled water into the radiator.

Start the Tacoma for a period of five minutes with the radiator cap off. This circulates the fluid through the engine and dispels air trapped in the system. Stop the engine, top off the radiator with a 50/50 mix of coolant and distilled water. Place the radiator cap back onto the Tacoma.

Items you will need

  • Ramps

  • Wheel chuck

  • Drain pan

  • 12 mm socket

  • Ratchet

  • 2 gallons antifreeze

  • 2 gallons distilled water

 How to Change the Thermostat in a Toyota Tundra

Make sure the engine and radiator are completely cool before starting this procedure. Disconnect the battery ground from the terminal.

Drain the coolant from the cooling system. Store the coolant in a container that can be securely sealed or properly dispose of the coolant.

Loosen and remove the three nuts that old the water inlet in place. Take the water inlet from the water inlet housing.

Lift the thermostat out with its gasket. Remove the gasket and discard it.

Set a new gasket in the thermostat. Position the thermostat with the jiggle valve facing up.

Replace the water inlet and set the nuts in place. Torque the nuts to 14 foot pounds.

Fill the engine with the recommended type and mix of coolant. Start the engine and check for leaks. Add coolant as needed once it has had a chance to circulate.

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 Toyota Tercel

Removing the Old Thermostat

Open your hood, and disconnect the negative battery cable before you get started. Loosen the terminal nut with the pliers, and lift the cable from the terminal. If your engine has been running recently, let it cool for at least 30 minutes.

Place a drain pan or another suitable container underneath the front of the engine bay. Look closely underneath the radiator to find the radiator drain plug.

Use the flat head screw driver to remove the plug and let the coolant drain. Cover the coolant and keep it in a safe place.

Unhook the electrical connection attached to the water inlet hose. Remove the two mounting bolts with the pliers or the socket wrench to unhook the housing and access the thermostat.

Remove the thermostat and the gasket. Pay attention to the mounting position of the thermostat. If the new thermostat is installed backwards (It's possible.), you can cause serious problems.

Installing the New Thermostat

Insert the new thermostat into the housing in the exact position as the old one. Make sure the bleed valve is facing up.

Attach the new gasket and the water inlet hose. Tighten the mounting bolts to 43-inch lbs. of torque.

Reinstall the drain plug and refill the cooling system with the coolant you drained unless it is dirty. If it's dirty or contaminated, go ahead and replace it if it's convenient.

Reconnect the negative battery cable, and start the engine. Let the engine idle for about 10 minutes or until it reaches normal operating temperature. (Pay attention to your temperature gauge.)

Check underneath for leaks. Keep a close eye on your temperature gauge for the next few days to make sure everything is working correctly.

Items you will need

  • Pliers

  • Floor jack (optional)

  • Jack stands (optional)

  • Drain pan or sealable container

  • Flat head screwdriver

  • Socket wrench

  • Replacement thermostat

  • Replacement gasket

  • Torque wrench

  • Funnel

 How to Change a Thermostat in a 2001 Toyota Tacoma V6

Drain Radiator

Wait for the engine to cool down to prevent burns caused by hot coolant. Open the hood and use a socket wrench to disconnect the negative battery cable.

Open the radiator cap. Place a container beneath the radiator drain plug located at the front passenger's side of the radiator. To prevent spillage, attach a piece of 3/8-inch tubing to the drain plug.

Turn the drain plug counterclockwise to open it. The valve may be tight require the use of pliers to open it. Open the radiator cap to allow air to enter the system, making the coolant drain faster.

Move the container underneath the engine block drain plug, just below the oil filter. If coolant doesn't drain when you remove the plug, insert a screwdriver into the hole to break the seal.

Close the radiator drain plug and replace the engine block drain plug when the coolant has completely drained.

Replace Thermostat

Locate thermostat housing by following the lower radiator hose to where it connects to the engine.

Unscrew the two nuts that hold the housing to the engine with a socket wrench. Pull the housing off the engine. The housing will likely be stuck to the engine so you will need to gently tap it with a rubber mallet to break it free. Once you detach the housing, some coolant will spill so be prepared for that with a drip pan.

Remove the thermostat and ensure the attaching surface of the thermostat housing is clean. If traces of the old gasket are stuck to the housing, use a flat head screwdriver to remove the residue.

Insert the new thermostat into the engine with the spring facing towards the engine. Ensure that the small pin attached to the outer rim of the thermostat is positioned at the top.

Reattach the housing and replace the two nuts.

Replace the coolant. Fill the radiator then fill the overflow reservoir to the full mark. If the drained coolant is in good condition, you can reuse it.

Reconnect the negative battery cable. Start the vehicle and let it run with the radiator cap off until the thermostat opens. Turn on the truck's heater and set it to the hottest temperature. You can tell when the thermostat opens by touching the top radiator hose. Once it feels hot to the touch, the thermostat is open, and coolant is flowing.

Turn off the engine and add coolant to the radiator until the fluid reaches the rim of the radiator filler neck. Squeeze the top radiator hose to push air out of the system and add more coolant if necessary. Replace the radiator cap.

Start the engine and let it run several minutes while you check for leaks.

Items you will need

  • Container

  • 3/8-inch tubing

  • Socket set

  • Pliers

  • Rubber mallet

  • Flat head screwdriver

  • Drip pan

 How to Change the Thermostat in a Toyota Corolla

Remove the cover on the right side of the under-engine. Drain the engine coolant into a sealable container.

Take out the fan and the V-belt on the generator, then remove the generator assembly. Remove the two nuts that hold the water inlet in place and then pull the water inlet.

Lift out the thermostat and remove the gasket. Clean the gasket mating surfaces thoroughly of dirt and old gasket material.

Put a new gasket on the thermostat, then install the thermostat so that the jiggle valve is on top. Make sure the thermostat is set within 10 degrees to either side of the prescribed position.

Connect the water inlet and set the two nuts in place. Tighten the nuts to 8 foot pounds.

Set the generator assembly in place. Refill the engine with coolant. Start the engine and check for leaks. Replace the right side cover under the engine.

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 Toyota Tacoma

Make sure the engine and radiator are completely cool, then drain the coolant from the engine. Store the coolant in a suitable container.

Take off the lower radiator hose, then remove the two nuts as well as the water inlet. Lift the thermostat and its gasket from the water pump.

Remove the used gasket from the thermostat and discard it. Clean the gasket mating surfaces of any gasket material or dirt. Set a new gasket on the thermostat.

Line up the jiggle valve on the thermostat with the protrusion of the water inlet housing. Set the thermostat in position in the water inlet housing.

Put the water inlet in place and secure it with the two nuts. Torque the nuts to 20 ft. lbs. Reconnect the lower radiator hose.

Refill the engine with coolant to the recommended levels. Use the recommended coolant and mix.

Start the engine and allow it to run for a few minutes. Check for leaks and make the necessary adjustments. Turn off the engine 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