Where is the thermostat located at on a Chevy Trailblazer

Hi,

Removing the thermostat isn't too hard to do. This will also be a good time to flush and refill the cooling system with new coolant. Also, make sure to inspect cooling system hoses to make sure they are good.

To get you started, here is a link that shows how to flush the cooling system:

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

Also, here is a link that shows in general how the thermostat is replaced. You can use this as a guide.

https://www.2carpros.com/articles/replace-thermostat

The directions specific to your vehicle are in the pics located at the bottom. I included the directions and pics related to the procedure.

Make sure to use the correct type of engine coolant. If the vehicle is still using Dexcool (GM Coolant) make sure not to mix it with a different type.

I hope this helps. Let me know if you have other questions.

Take care,
Joe

Did you change the coolant temp. Sensor, or the thermostat? If the PCM sees that coolant temp is below thermostat regulating temp, it will set an error code. This means the PCM sees coolant temp. At say 177 degrees, while it should be at 195. This is caused by either the thermostat or the coolant temp. Sensor that is misreading the engine temp.

Engine Coolant Thermostat Replacement (4.2L Engine)
Tools Required
J 38185 Hose Clamp Pliers

Removal Procedure
Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .
Remove the generator. Refer to Generator Replacement .

Loosen the outlet hose clamp at the thermostat housing (1). Remove the outlet hose from the thermostat housing.

Remove the thermostat housing bolts.
Remove the thermostat housing from the engine block.
Clean all of the surfaces of the thermostat housing.
Clean the sealing surface of the engine block.
Installation Procedure

Install the thermostat housing to the engine block.
Notice: Refer to Fastener Notice in the Preface section.

Install the thermostat housing bolts.
Tighten
Tighten the bolts to 10 NÂ m (89 lb in).

Lubricate the inner diameter of the radiator hose with engine coolant.

Install the outlet hose to the thermostat housing (1). Secure the hose with the clamp.
Install the generator. Refer to Generator Replacement .
Fill the cooling system with specified coolant and concentration. Refer to Cooling System Draining and Filling .
Inspect all sealing surfaces for leaks after starting the engine.

Engine Coolant Thermostat Replacement (4.2L Engine)
Tools Required
J 38185 Hose Clamp Pliers

Removal Procedure
Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .
Remove the generator. Refer to Generator Replacement .

Loosen the outlet hose clamp at the thermostat housing (1). Remove the outlet hose from the thermostat housing.

Remove the thermostat housing bolts.
Remove the thermostat housing from the engine block.
Clean all of the surfaces of the thermostat housing.
Clean the sealing surface of the engine block.
Installation Procedure

Install the thermostat housing to the engine block.
Notice: Refer to Fastener Notice in the Preface section.

Install the thermostat housing bolts.
Tighten
Tighten the bolts to 10 NÂ m (89 lb in).

Lubricate the inner diameter of the radiator hose with engine coolant.

Install the outlet hose to the thermostat housing (1). Secure the hose with the clamp.
Install the generator. Refer to Generator Replacement .
Fill the cooling system with specified coolant and concentration. Refer to Cooling System Draining and Filling .
Inspect all sealing surfaces for leaks after starting the engine.

Well, I cut off part of the picture.

I did see a bulletin about the temp gage reading, higher than normal, the outside temp is up a little, with stop and go or slow moving traffic. There is a software update. I guess the calibration may turn on the cooling fan quicker and keep it on longer. I don't know if that bulletin has anything to do with your problem, I just saw it.

To add to great advice by jdl123:

The thermostat is an assy. That is, you buy the thermostat and housing, not just thermostat.

You have to remove alt. To get to it.

If you are getting an error code "coolant temp below thermostat regulating temp", then you may have a bad coolant temp sensor.

REMOVAL:
Remove the necessary coolant from the radiator.
Remove the alternator.
Loosen the outlet hose clamp at the thermostat housing.
Remove the outlet hose from the thermostat housing.
Remove the thermostat housing bolts.
Remove the thermostat housing from the engine block.
Clean all of the surfaces of the thermostat housing.
Clean the sealing surface of the engine block.

INSTALLATION:
Install the thermostat housing to the engine block.
Install the thermostat housing bolts and tighten to 89 inch lbs. (10 Nm).
Lubricate the inner diameter of the radiator hose with engine coolant.
Install the outlet hose to the thermostat housing. Secure the hose with the clamp.
Install the alternator.
Fill the cooling system with specified coolant and concentration.
Inspect all sealing surfaces for leaks after starting the engine.

Thanks for using 2CarPros.com!

Hello,

Here is a guide to walk you through the steps of changing the thermostat and diagrams below to show you how on your car

https://www.2carpros.com/articles/replace-thermostat

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.