Went to add coolant to reservoir there was oil in it! checked radiator only coolant disconected reservoir from radiator until i get it fixed. think previous owner added oil here. any other ideas?

no
as the coolant heats it expands and the radiator cap lets off into the reservoir that fills the reservoir
as the coolant cools down the radiator cap allows the low pressure in the cooling system to draw coolant back from the reservoir
To need to add coolant indicates that the draw back process is not happening possibly from the overflow hose not sealing off properly and allowing air back in and not drawing from the reservoir
check the reservoir for cracks as well

Cooling fans not turning on, check to make sure the cooling fans are running when overheating occurs. Not enough coolant in the cooling system, check the coolant reservoir make sure the coolant is at at the maximum level when combustion engine is completely cool,if your coolant is low add coolant to the maximum level. (1)Start combustion engine, let it warm up but not over heat. Turn off combustion engine, when it cools completely the coolant reservoirs level will be lower . Add more coolant and keep repeating (1) until the coolant level stays the same after combustion engine completely cools down.Sensor that tells the cooling fans to turn on defective. Non functioning thermostat. Broken impeller inside Water Pump. Clogged radiator. Clogged water jackets in combustion engine. Broken drive belt. Radiator has something blocking the cooling fins(possibly a plastic bag that went against the cooling fins when driving)

if you dont see radiator cap on radiator.you pour coolant in the coolant reservoir jug until coolant level stay on full cold mark.when adding coolant to coolant reservoir jug when coolant level stop dropping stay at full cold mark.you have correct amount antifreeze in radiator.

WAIT UNTIL YOUR ENGINE IS COLD,YOUR RADIATOR PRESSURE CAP IS LOCATED ON THE COOLANT OVER FLOW RESERVOIR, THATS WHERE YOU ADD COOLANT WHEN COOLANT LOW,YOU POUR COOLANT IN THE OVER FLOW RESERVOIR UNTIL COOLANT LEVEL REMAIN AT FULL COLD MARK DONT OVER FILL OVER FLOW RESERVOIR, WHEN COOLANT LEVEL STOP DROPPING WHEN ADDING COOLANT AND COOLANT LEVEL STAY AT COLD MARK ON THE RESERVOIR YOU RADIATOR HAS THE CORRECT COOLANT LEVEL IF COOLANT LEVEL KEEP DROPPING CHECK FOR COOLANT LEAKS AROUND RADIATOR AND THE TOP AND BOTTOM RADIATOR HOSES, LOOK FOR COOLANT LEAK AT WATER PUMP GASKET OR SEAL OR LEAK AT WATER PUMP WEEP HOLE IF YES REPLACE WATER PUMP.

• One is the radiator and the other is an overflow tank. Sometimes anti freeze will back pressure a bit and need somewhere to go and other times the antifreeze gets low in the radiator. That is the purpose of the radiator.
• Put the antifreeze in the radiator fist and then add to the reservoir. Pay attention to the cold/hot level fill on the overfill tank.
• You need to find out where all that antifreeze went to if the radiator was empth. Pull the dipstick and look for a chocolate milk look on the oil. This would be a head gasket or a cracked head.
• Otherwise keep an eye out for a leak and repair it soon.
• Hope this helps and thank you for using FixYa.

Regards, Tony

YOU NEED BLEED COOLANT SYSTEM.CHECK COOLANT LEVEL IN RADIATOR.ADD MORE DEXCOOL UNTIL COOLANT LEVEL IS CLOSE TO RADIATOR SPOUT.CRANK ENGINE LET IDLE UNTIL TOP RADIATOR HOSE GET HOT.WATCH TEMPERATURE GAUGE.IF TEMPERATURE GAUGE START RISING TO HOT ZONE.TURN OFF ENGINE.LET COOL DOWN.USE LARGE RAG SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL ALL PRESSURE RELIEVED.REMOVE RADIATOR CAP.ADD MORE COOLANT.CRANK CAR AGAIN LET IDLE UNTIL TOP RADIATOR GET HOT.KEEP EYE ON TEMP.GAUGE ALSO.WHEN TEMP.GAUGE STOP CLIMBING.YOUR COOLANT SYSTEM BLED.WHEN DONE LET CAR SET A WHILE CHECK COOLANT LEVEL.ALSO FIRST THING IN THE MORNING CHECK COOLANT LEVEL AGAIN.AND BESURE ADD COOLANT IN THE OVERFLOW JUG TO THE COLD MARK.DONT OVER FILL THE COOLANT RESERVOIR JUG.WORK SAFELY DONT GET SCALDED.

3.1 liter?

If so the level sensor is in the reservoir. Sometimes the level gets stuck if the coolant gets low. Some gentle whacking of the reservoir with a rubber mallet is usually enough to get the light to turn out.

3.8 liter?

When the car is cold remove the radiator cap on the passenger side of the radiator. Add coolant until full.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The overheating is caused by the sludge. It is very easy to correct this problem. Remove the radiator cap and open the drain valve at the bottom of radiator. If possible, remove the reservoir and flush out with water. Make sure to get all sludge out of reservoir, then reinstall. Once the radiator stops draining, insert water hose (without nozzle) and turn water on. Keep the drain valve open. Run water through radiator until it runs clear. Once it runs clear, start the engine and let it run while keeping the water running through radiator. Allow engine to run until the thermostat opens up. Continue running water through radiator with engine running until the water from drain runs clear. Once you have done that, turn off the engine. Close the drain valve and refill radiator with proper mixture of coolant and water. Once radiator is filled, start engine and let circulate through engine. Coolant level will drop as the coolant starts circulating. Shut off engine and top off radiator. Fill the reservoir with the required amount of coolant. Testing the coolant at least once a year will help prevent this from happening again. Coolant should be replace a minimum of five years, less if coolant bottle specifies.

either a leaky head gasket or someone put oil in the overflow, it happens, clean it out drain the coolant from the entire system and refill with new long life antifreeze, also add a can of good radiator sealer.

Your waterpump belt is broken.... or your radiator is block Check thermostat is working. If this 3 things is Okay your headgasket is blown or one of the heads is crack.