Car is running hot and the heater quit working. i have a thick oily substance in my radiator resservoir. this car is a 1999 Saturn sl. in the radiator reservoir it has a brownish thick liquid and when the car gets hot it oozes on the side and i have a puddle of thick brownish liquid on the ground.

Make sure the fan temp sensor is working, that is does the coolant fan come on when it gets hot.

Very carefully , Open radiator cap fill coolant , run engine with heater on hot and blower on , repeat 3 times .

Coolant is oil based. The oily mess in the overflow could be very old coolant. Or it could be engine oil from a leaking head gasket.
The rusty stuff on the floor inside the car could be from a leaking heater core.

For car running hot and overheating issues,i suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems :----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving? http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping? http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

you either have a closed thermostat or a blockage in the radiator

If you have check all the fluids and the water pump for operations, make sure your electronic fan is working then look in your radiator for a oily substance unfortunately that year and the 1998 had a head gasket problem which can result in a total engine rebuild if continued driving.

Look at your radiator from the front of the engine,

On the right side of the radiator you will see it's plastic, near the nut that holds the transmission lines going to the radiator you may notice it's cracked and leaking through there,

Let the car idle up to temperature and when it's hot race the engine and you may see that coolant is leaking from the plastic end of the radiator which means you will have to get a new radiator.

the oily substance you talk about is antifreeze, your heater core is damaged and leaking in the form of mist and going to your windshield you must replace your heater core in the dash generally behind the glove box.

Check your electric cooling fan is cutting in when stationary. Air flowing through your radiator whilst driving keeps your engine cool. There is no airflow when stationary, so cooling fan is used to compensate, sounds like yours isnt working.

There are generic block heaters available that fit in the radiator hose and keep the water warm thus heating the block as well.