2003 Pontiac Gran Prix GT 3.8L Thermostat replacement

Make sure radiator is full and that all hoses are ok. Then make sure that the thermostat is opening and that your water pump is circulating coolant through the radiator which must not be clogged. Till you find issue run your heater full blast with window open to add additional cooling to engine.

The answer to that question is TOTALLY different depending on which engine your Gran Prix is equipped with. The choices are:

> V6-3.8L VIN 2
> V8-5.3L VIN C
> V6-3.8L SC VIN 4

This is really must know information - especially if you are asking somebody for help with your engine, engine accessories, or engine control systems.

If you haven't replaced the thermostat yet, try that next.

Please see my tip at http://www.fixya.com/cars/r5929960-s_thermostat . These are generic instructions. If you get stuck or need specific instructions for your car, please get back to me with model, year and engine info.

this one? That is the check engine light.



Sounds like you may have a code for insufficient engine operating tempurature. This is usually caused by a bad thermostat. Its pretty common to see this problem on newer GM vehicles. A new thermostat will take care of it 99% of the time.

To find the thermostat follow the upper hose to the engine. The thermostat will be behind the metal housing that the hose attaches to on the engine.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Fig. The thermostat on this 3.1L is mounted horizontally and uses an offset housing/water outlet



Fig. Exploded view of the thermostat arrangement-3.8L engines




Fig. Thermostat arrangement-3.4L (VIN E) engine




Fig. The thermostat and water inlet assembly are combined in one assembly and must be serviced together-3.5L (VIN H) engine




It is usually possible to leave the radiator hose attached and simply remove the thermostat housing (also called a water outlet) and flex the radiator hose enough to service the thermostat. It is good practice, however, to remove the radiator hose so the thermostat housing can be given a thorough cleaning. Debris on the thermostat housing sealing surface can cause leaks.

Some applications may have electrical connections to sensors which mount in the thermostat housing. Use care when detaching these connectors.

Unfasten the thermostat housing bolts and remove the housing.





Remove the thermostat by simply pulling out; then remove and discard the gasket from the thermostat.



I really hope help with this. Good luck (remember rated this help).

The thermostat is located just under the exhaust manifold you will see that a metal pipe leads from the water pump to where the thermostat housing is. You must to remove two screws from where this pipe meets the housing and it is a pain to do unless you remove the exhaust manifold or have small hands.

If your talking about the cooling system some have two and some have only one, there will be one on the thermostat housing and there may be one by the water pump.

Mine usually runs right smack in the middle. If it's middle or under you are fine. If it's over half way, then you need to change your thermostat, or you cooling fan isn't kicking on when it should. There is a temp sensor that controls the fan.

Thermostat, cooling fans, water pump, rad (not plugged wirth scale)

check evap vent solenoid alot stick on these cars.