Follow the upper radiator hose from where it leaves the radiator to where it enters the engine block on top of the engine. This is where the thermostat will be located. You’ll need to remove the hose and the housing (2-3 bolts) that covers the thermostat to replace it.

While there are a variety of reasons your Pontiac Grand Prix is overheating, the most common 3 are a coolant leak (water pump, radiator, hose etc.), the radiator fan, or a failed thermostat. Coolant leak (water pump, radiator, hose etc.)

2007 Pontiac Grand Prix Thermostat – from $6.49+ | AutoZone.com.

How to Change Coolant in a Pontiac Grand Prix

1. Raise the hood of the Grand Prix and make sure that the engine has cooled completely.
2. Place a bucket or drain pan under the drain plug on the radiator.
3. Raise the car enough to remove the jack stands.
4. Add a 50-50 mix of distilled water and anti-freeze to the radiator.

2006 Pontiac Grand Prix Thermostat – from $6.49+ | AutoZone.com.

The thermostat housing is located in the upper radiator hose.

The average cost for a Pontiac G6 thermostat replacement is between $244 and $280. Labor costs are estimated between $136 and $172 while parts are priced at $108. This range is based on the number and age of Pontiac G6’s on the road.

It is in the back of the water pump and you may have to remove the exhaust manifold to access it.

2009 Pontiac G6 Thermostat – from $16.99+ | AutoZone.com.