Hello jonah! i need to replace a thermostat on my 2004 chevy colorado, 3.5 litre engine can you tell me where it is located on my engine?

Check this procedure for Canyon, Colorado 2004-2005 - Removal & Installation

1. Drain the cooling system.
   
2. Raise and support the vehicle only high enough to access the thermostat housing through the wheelhouse.
   
3. Remove the left wheelhouse liner.
   
4. Remove the radiator inlet hose from the thermostat housing.
   
5. Remove the thermostat housing bolts.
   
6. Remove the thermostat housing from the engine block.
   
7. Clean and inspect the thermostat housing.
   
8. Clean and inspect the sealing surface of the engine block.

1. Position the thermostat housing to the engine block.
   
2. Install the thermostat housing bolts and tighten to 89 inch lbs. (10 Nm).
   
3. Connect the radiator inlet hose to the thermostat housing.
   
4. Install the left wheelhouse liner.
   
5. Lower the vehicle.
   
6. Fill the cooling system.
   
7. Inspect all sealing surfaces for leaks after starting the engine.

1. Drain the cooling system.
   
2. Raise and support the vehicle only high enough to access the thermostat housing through the wheelhouse.
   
3. Remove the left wheelhouse liner.
   
4. Position the hose clamp pliers to the clamp to remove the radiator inlet hose from the thermostat housing.
   
5. Remove the thermostat housing bolts.
   
6. Remove the thermostat housing from the engine block.
   
7. Clean and inspect the thermostat housing.
   
8. Clean and inspect the sealing surface of the engine block.

1. Position the thermostat housing to the engine block.
   
2. Install the thermostat housing bolts and tighten to 89 inch lbs. (10 Nm).
   
3. Connect the radiator inlet hose to the thermostat housing.
   
4. Install the left wheelhouse liner.
   
5. Lower the vehicle.
   
6. Fill the cooling system.
   
7. Inspect all sealing surfaces for leaks after starting the engine.