I have sludge in the coolant in my l997 Olds Aurora/

Dirty throttle body, restricted injectors, bad engine coolant temperature sensor, weak ignition coil or coils .

Either the low sensor in the tank is stuck, you have not connected the sensor wire properly or you bought the wrong tank.

Could work its way into radiator and clog it up resulting in overheating.

It is located on the passenger side above cv axle, a few inches from the output speed sensor. Follow the coolant hose down below and you'll find it ( it may be covered in fluid)

There isn't one. The computer uses the engine coolant temperature sensor for both fuel delivery data and fan activation. If you turn on the A/C or pull the coolant temp sensor connector off while the engine is running, the fan(s) should come on. If not, you may have a bad relay or fan motor.

The coolant level sensor is inside the coolant bottle. It is not replaceable separately. You will have to replace the reservoir to replace the sensor.

The engine coolant temp. sensor(ect)is located at the
rear of the engine below the thermostat housing (3.8L
The 4.0L is at the rear of engine top of the manifold
firewall side. Hope this helps.

always buy the same color coolant as is in the car as in red/red green/green blue/blue or consult the dealer or your owners manual,mixing types/colors will get you a plugged radiator and an expensive cleanout of the system,because it turns to a jello type consistency

check the hoses going into the firewall. they goto the heater core on the inside of the car.

The coolant level sensor in the coolnat reservior is shorted out . The coolant level when driving is circulating fine . The coolant must be going just past the sensor and triggering it off.