I think there is air in my Saturn SC2 radiator. I replaced the water pump, thermostat and hoses. The heater works fine, but the temperature gauge is not running as cool as before. since there is no cap on the radiator, I can't tell if there is air trapped in the top chamber or not.

sounds like the thermostat may not be opening.

heater hoses run from the rear of the block to the water pump. One hose into the heater should be hotter than the other because heat is transferred in the heater in the car. . The cooling system draws water from the bottom of the radiator ( water pump inlet)which is always cooler than the top hose and dispenses it throughout the engine and heads including the heater core. It is then pushed past the thermostat with all the heat from the engine to the top of the radiator where it is cooled down by the air passing through the radiator . Check that the air vent for the cabin is set to recirculated cabin air and not fresh air from the outside as it will require recirculated air to increase in temperature to work properly

There are other things to test before we have the engine spread all over the yard. Cooling fan operation. Yes the thermostat hot air in heater just means hot water. start with a cold engine then start and run at a high idle if heats quickly upper radiator hose hot lower cold good but reverse no flow. remove and test thermostat (not replace) put on stove boil water and watch it open once center piece is moving check with thermometer it should agree with stamp number on thermostat. if good check for slipping fan belt. check for air restrictions on radiator and water flow.

While it doesn't seem likely, if you've changed, or had the thermostat changed.... I'd say you got a faulty thermostat. I am curious as to what your temperature gauge says the temperature of the engine and coolant is.. If your gauge is showing hot, I can think of two more possibilities... the water pump isn't pumping right... and, if the water pump isn't working right, the problem can be a cracked head or block, which can cause an airlock in the coolant system. Check the coolant or radiator cap.

Faulty coolant temperature sensor and a faulty heater control valve.

how about the coolant temp sensor, they had alot of problems with that sensor and also the plug for it,some have two of these sensors side by side, one for the gauge and the other for the fan, i would replace these first and go from ther good luck,

It sounds like you have air in the Cooling system and the bars leak permanent seal does not help. The sealer creates restrictions through out the water jackets and can cause the thermostat to stick. Replace the radiator cap and run the truck with the radiator cap on the first click and keep an eye on the over flow tank, refill the over flow as needed and make sure you have the heater on the highest setting to work out all the air in the system. Once all the air has worked it's way out of the system, then you can close the radiator cap to the second click to ensure full pressure is built up in your cooling system. Good luck and keep me posted.

the temperature guge will be higher than normal. there may be a squealing sound which may indicate that the seals on the pump have perished. I am not sure if you have cold weather where you are, if you don't try running the car for a while to watch the progress of the temperature gauge. You may also have an airlock in your radiator??? The only real way to be sure if your water pump is fuctioning correctly is to remove it and check the seals.

Good luck

It sounds as if you may have an air pocket in the system, alot of your saturn and gm vehicles have air bleed on or near the thermostat housing. As you are filling the system you will need to have this bleeder open until a steady stream of coolant comes out.

you probably have air trapped in the system. Have dealer or radiator shop bleed system.

I assume your cooling fan is working.

what engine v6 or v8?

SECTION 303-03: Engine Cooling 2001 Lincoln LS Workshop Manual
DESCRIPTION AND OPERATION Engine Cooling The cooling system components include the:

• block heater (optional)
• cylinder head temperature sensor
• fan blade, fan motor and fan shroud assembly
• radiator
• pressure relief cap
• degas bottle
• radiator draincock
• water pump
• oil cooler (optional)
• water thermostat

The water thermostat:

• controls the engine coolant temperature.
• allows quicker engine warm-up.

The degas bottle:

• provides a location for system fill.
• contains coolant expansion and system pressurization.
• provides air separation during operation.
• replenishes the engine coolant to the system.

The fan blade draws air through the radiator to help cool the engine coolant.
The fan motor:

• operates only when the engine is running.
• will not operate when the engine is off.

The engine coolant flows:

• from the lower radiator hose to the water pump.
• from the water pump to the engine block and the cylinder heads.

A closed water thermostat returns the engine coolant to the water pump. An open water thermostat allows the engine coolant to flow to the radiator.
Unsatisfactory coolant materials:

• Alcohol-type antifreeze does not provide adequate water pump lubrication.
  • has lower boiling point
  • reduced antifreeze protection
• Alkaline brine solutions will cause serious engine cooling system damage.

The cylinder head temperature sensor provides a signal to the temperature gauge.

• will invoke failsafe cooling.

The optional block heater:

• electrical heating element is installed in the block cooling jacket.
  • uses a standard 110V (220V in Europe) electrical supply
• keeps the engine coolant warm during cold weather.

The auxiliary water pump (3.9L only):

• provides heater coolant flow boost.
• has a secondary function of providing engine-off cooling.