How to replace thermostat in a 06 Pontiac G6 3.5L?

Here is a guide that will show you what you are in for when doing the job along with a diagram (below) of what it will be like on your car.

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

Here is the instruction from the book

THERMOSTAT HOUSING REPLACEMENT (3.5L )

Removal Procedure

Fig. 114: Thermostat & Housing Outlet
Courtesy of GENERAL MOTORS CORP.

1. Drain the cooling system. Refer to Draining and Filling Cooling System.
2. Remove the air cleaner outlet duct. Refer to Air Cleaner Intake Duct Replacement for the 3.5L engine.
3. Disconnect the surge tank hose from the coolant outlet.
4. Remove the thermostat housing to intake manifold bolts.
5. Remove the thermostat housing outlet and thermostat.

Installation Procedure

Fig. 115: Thermostat & Housing Outlet
Courtesy of GENERAL MOTORS CORP.

NOTE: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring
replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants or
corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may
damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the thermostat and housing outlet.

NOTE: Refer to FASTENER NOTICE .

2. Install the thermostat housing bolts.

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken

It depends on which one you have the 3.5L is on the end of the inlet manifold and the 3.9 is on the side by the water pump. Both have hoses going to them. You need to drain the cooling system down, remove the hose from the housings, remove the bolts and remove the thermostat. REverse teh procedure for installation. Torque bolts to 25nm or 18 ' lbs.

Remove the air cleaner housing and then remove house. Remove the bolts and to remove thermostat housing. When you fill, open bleeder valve on housing until coolant comes out. Re-tighten and warm up engine and open bleeder slowly until all air is out. Good luck.

It sounds like it may have a defective thermostat but I would take it back to the guy that installed it so he can at least check for a problem. You might want to insist that he use OEM parts next time.

Do you have a 3.5 3.6 or 3.9L engine?Let me know so I can get you the correct information.

Why is the engine light coming on. Usually wherever you go will have a package deal for the flush. 60 to 100 and depending on the price of the thermostat another 50 to 100 bucks