Replace cooling system thermostat

check the coolant level,thermostat may need replacing(stuck closed),the cooling fans may not be working,try jumping the electrical prongs on the cooling fan motor with the connector unhooked.it should run if not then the fan motor will need replacing,it could also be a head gasket problem you can have a block test on the cooling system to check this out.

Hello! Replace the thermostat, it is defective...I would suggest flushing the cooling system with the heat set to high...Your engine requires Dex-Cool anti-freeze...It, due to electrolysis, has a tendency to "clump" blocking proper flow...Drain the cooling system...Fill with plain water...Allow engine to heat up and when the thermostat opens shut down and drain...Do this three times or until water is clear...Replace thermostat and refill with Dex-Cool...Allow all air to escape before installing cap...

Guru............Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

the cooling systems consists of a radiator, radiator cap, water pump, thermostat, hoses, heater core and sometime a heater control valve that open water lines to heater core. You may need a cooling system flush if water pump, radiator have been replaced. flush the system.change the thermostat and have the heater core checked too if you can get to it.
does the cooling fan kick on to cool the radiator..check that too.replace radiator cap and check cooling fan yourself...let me know if need anything else.
Thanks for using fixya and please vote.

3.2L & 3.5L Engines

1. Disconnect negative cable
   
2. Drain cooling system.
   
3. Raise vehicle on hoist.
   
4. Disconnect electrical connectors from engine oil and power steering pressure switches.
   
5. Disconnect radiator and heater hoses from thermostat housing.
   
6. Remove thermostat housing bolts.
   
7. Remove housing, thermostat, and gasket.
   

To install:

1. Position gasket on thermostat and housing.
   
2. Install thermostat housing, gasket and mounting bolts onto block. Tighten attaching bolts to 105 inch lbs. (12 Nm).
   
3. Install radiator hose.
   
4. Install bypass hose.
   
5. Connect electrical connectors from engine oil and power steering pressure switches.
   
6. Connect negative cable.
   
7. Fill cooling system.
   
8. Inspect for leaks.
   
9. Lower vehicle on hoist.
   

For 1999 Oldsmobile Aurora 4.0L SFI DOHC 8cyl check thie how to replace a Thermostat:

Parts:
1. Thermostat

Tools:
1. 3/8 in. Drive Ratchet
2. Needle Nose Pliers
3. Screwdriver
4. Cooling System Pressure Tester
5. Socket Set
6. Radiator Hook Tool

Steps:
Step 1 Open the hood and locate the vehicle’s radiator.
o Tip: Make sure the vehicle has cooled down before inspection.
o Tip: Safety Tip:Always wear safety glasses when working on your vehicle. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or safety shoes.


Step 2 Remove the vehicle’s radiator cap and use a radiator pressure tester to check for leaks.

Step 3 Drain out some of the engine coolant in the radiator so the coolant level is below the thermostat housing to prevent leaking when replacing the thermostat.

Step 4 If necessary, remove the upper radiator hose.
o Tip: A twisting motion may help to initially break the upper radiator hose loose. You can also use a flathead screwdriver to help pry the hose off. Make sure not to damage the hose.

Step 5 Remove the thermostat housing bolts.

Step 6 Remove the thermostat housing.

Step 7 Remove the thermostat.
o Tip: Make sure to note the way the thermostat is installed. Installing the thermostat backwards will affect how the cooling system performs.

Step 8 Clean the mounting surfaces. Install the new thermostat as it was removed and always use a new thermostat gasket.

Step 9 Reinstall thermostat housing and tighten mounting bolts evenly. If applicable, reconnect the upper radiator hose.

Step 10 Refill the cooling system with coolant.

Step 11 Start the vehicle with the radiator cap off and allow the engine to run for several minutes. This allows the air bubbles to escape the cooling system.

Step 12 Reinstall the radiator cap.

Step 13 Run the engine until up to normal operating temperature. Remember to keep an eye on the temperature gauge to prevent overheating.


Hope helps (remember rated)

Could be both your water pump and thermostat are faulty. Start with the simple and replace the thermostat and also did the engine over heat while you were stopped or in stop and go traffic, if you were then you may have a blown fuse or bad cooling fan relay that needs to be addressed. Check to make sure your Cooling fan is working, you can test this buy turning on your A/C on full and the fan should come one the same time your A/C clutch activates. If the fan does not function, inspect the electrical system to the cooling fans and replace the thermostat to ensure there will not be any issues in the summer time. Thermostat are know to go bad when they are over heated.
Thank you for using FIxya and good luck

The 2.7L engine lower radiator hose, connects to the thermostat housing.

To Remove:
1.Disconnect the Negative battery cable.
(Engine COLD!)

1. Drain cooling system.
2. Remove radiator lower hose from thermostat housing.
3. Remove nuts from heater tube flange studs.
4. Loosen starter bolt at heater tube bracket.
5. Pull heater tube out of thermostat housing and position out of the way.
6. Remove bolt and two studs.
7. Remove thermostat housing, O-ring and thermostat.
8. Remove thermostat housing bolts.

To install:
A.Clean gasket sealing surfaces.
B.Install thermostat with the bleed valve located at the 12 o'clock position, between tabs on seal.

1. Install thermostat and seal into thermostat housing .
2. If removed, install two studs.
3. Install thermostat, thermostat housing and O-ring and bolt. Tighten attaching bolts to 105 inch lbs.(12 Nm).
4. Lubricate new heater return tube O-ring with coolant.
5. Position heater return tube flange over two studs. Install nuts.
6. Tighten retaining nuts to 53 inch lbs.(6 Nm).
7. Tighten starter bolt to 40 ft. lbs. (54.3 Nm).
8. Connect the lower radiator hose to the thermostat housing. Install hose clamps.
9. Refill cooling system.
10. Inspect for leaks.
11. Connect negative cable.

3.2 and 3.5L engines:
Disconnect the battery cable. (Again engine COLD)

1. Drain cooling system.
2. Raise vehicle on hoist.
3. Disconnect electrical connectors from engine oil and power steering pressure switches.
4. Disconnect radiator and heater hoses from thermostat housing.
5. Remove thermostat housing bolts.
6. Remove housing, thermostat, and gasket.

The OEM thermostat is staked in place at the factory. To ensure proper seating of replacement thermostat, carefully remove the bulged metal from the thermostat housing, using a suitable hand held grinder. It is not necessary to restake the replacement thermostat, into the thermostat housing.

To Install:

1. Position gasket on thermostat and housing.
2. Install thermostat housing, gasket and mounting bolts onto block. Tighten attaching bolts to 105 inch lbs. (12 Nm).
3. Install radiator hose.
4. Install bypass hose.
5. Connect electrical connectors from engine oil and power steering pressure switches.
6. Connect negative cable.
7. Fill cooling system.
8. Inspect for leaks.
9. Lower vehicle on hoist.

From AutoZone Repair Guides

I feel this way, I can give you an accurate description, and have taken into account your safety.

After replacing the thermostat, you must bleed the air from the cooling system.

To bleed air from the 2.2L and 2.5L engines, remove the plug or sensor on the top of the thermostat housing. Fill the radiator with coolant until the coolant comes out the hole. Since the plug is made out of steel and the thermostat housing is aluminum, it is a good idea to apply an anti-seizing compound or Teflon® tape on the plug threads prior to installation. Install the plug and continue to fill the radiator. This will vent all trapped air from the engine.

Any trapped air in the heating system will have to be displaced by coolant. Once the cooling system is filled, with the radiator cap off, turn of the heater at it's highest setting. Start the engine and allow it to reach operating temp. You should see a drop in the coolant level as the air in the heating system is displaced by coolant. Add coolant to the proper level and replace the radiator cap.

Keep a close eye on the coolant level for at least the next couple of weeks. The cooling system is a "closed" system. Any significant decrease in coolant level indicates a problem.

If you have any questions, let me know.

Please take the time to rate this solution.

Drive safe and be warm.

clarkco

Have the cooling system flushed or remove the hoses from the firewall(when cool) and blow out heater core with compressed air-clogged heater core..