Thermostat Replacement On the 3.4 V6 Engine
2/20/2003

Alan (HaveBlue on the forums) shows you how he changed out his thermostat for a newer one.

For those of you who want or need to replace your old thermostat in your 3.4L engine.
Items you will need:
Thermostat
Thermostat gasket
1 gallon coolant (Toyota long-life is recommended)
1 gallon distilled water
Empty one or two gallon container
Pliers
Bucket or container to catch old coolant (minimum 2.5 gallon capacity)
Metric sockets (12mm, 17mm)
3/8” drive ratchet w/ 6” extension

If you have the TRD Supercharger with Dynamic Belt Tensioner, you will need to follow these instructions.
If you do not have the Dynamic Belt Tensioner, you can skip ahead to step 5.
Skid plate removal is not necessary, but it does allow for easier access to the lower radiator hose and drain valve.

1. Remove the radiator cap.
2. Locate the drain valve on the bottom of the radiator.

This is where it is beneficial to have the skid plate removed. Open the valve fully. Pliers may be required to break the seal and loosen the valve. Have your container ready to catch all the coolant as it drains.
3. Using a 3/8” ratchet, pull the Dynamic Belt Tensioner away from the belt and remove the belt from the supercharger pulley.

4. Using a 17mm wrench or socket, remove the bolt holding the belt tensioner and remove the tensioner.

5. After the coolant has stopped draining from the radiator valve, use a pair of adjustable pliers to move the spring clamp away from the radiator on the lower radiator hose. Pull the lower radiator hose away from the radiator. The pliers may need to be used to twist the hose and break the seal. Have a rag or container ready to catch the spilled coolant.
6. Use the 12mm socket and 6” extension to remove the three nuts holding the thermostat housing in place.

7. Place a rag under the thermostat housing and pull the housing away from the block.
8. Note the position of the jiggle valve (brass button). The new thermostat will need to be installed with the jiggle valve in the same location. Use a flat screwdriver to pry the old thermostat out of the block and be prepared for more coolant to spill out.
9. Clean out the housing and the block. Make sure you remove all remaining gasket material.
10. Apply the new gasket around the new thermostat. The gasket should have a groove that will fit around the outer edge of the thermostat.
11. Place the new thermostat in the block with the jiggle valve in the same location as the old thermostat. For reference, the jiggle valve should be within 15 degrees of the 12 o'clock position. Make sure the thermostat is seated and snug.
12. Place the thermostat housing on the three studs and secure it with the three nuts. DO NOT over tighten! The housing can fracture if over tightened. The torque setting on the nuts should not exceed 14 ft/lbs.
13. Secure the lower radiator hose to the radiator and seat the spring clamp on the hose.
14. Close the radiator drain valve completely.

If you have the Dynamic Belt Tensioner, use the following steps. Otherwise, skip to step 17.

15. Reinstall the belt tensioner.
16. Reinstall the belt under the tensioner and around the supercharger pulley. Make sure the drive belt is seated on the alternator pulley, supercharger pulley, and crank pulley.
17. Refill the radiator with 50/50 coolant (50% glycol, 50% water).
18. Leave the radiator cap off and start the engine. Let the engine come to normal temperature and turn the heater on. This will purge the system of any air that might be trapped within the system.
19. Fill the overflow reservoir about halfway with 50/50 coolant.
20. Continue to fill the radiator if the fluid level drops. Once it has stopped dropping, screw the radiator cap back into place and take it for a drive.

If you choose to do this task good luck, and if you have any questions  (HaveBlue) on the Yotatech Forum.

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