Someone put oil in the cooling system,what should i do?

Are you sure its oil? If you bought it used someone probably added Bars Leak or some other cooling system sealer which can appear as oil. Cadillac Northstar engines are well known for cooling system problems, and that is usually the first step people take. If it is oil that could indicate an intake manifold leak or a head gasket leak, although it usually results in coolant in the oil, not the other way around.

Methods to trouble shoot
(1) check thermostat device. if thermostat is stuck - not working half the water used in cooling system is missing once engine heats up which can lead to over heating. (may need mechanic to check this)
(2) check radiator has water in it . if it is low there may be a leak in cooling system somewhere check rubber hose and radiator are not leaking.
(3) check fan belt is engaging fan in front of radiator
(4) if electric fan check if fan activates once car has heated up
(5) check oil level of engine on dip stick. If low oil add some oil and re check oil dip stick. DO NOT PUT whole oil pack in (don't laugh I know someone who did this and has to go to mechanic and get oil removed)
(6) if rubber hoses blow off connectors then you may have a broken head gasket seal. A pressure test of the radiator will confirm this.
(7) Possible water pump failure. Check by taking cap off radiator and run engine see if water is flowing in radiator and test if water is heating up in the radiator. Remember to put cap back on radiator when finishing test.
(8) check if bubbles or oil are in radiator water this could indicate a blown head gasket problem also.

Have you owned the car for a long time?? Could it be possible that someone has put a bottle or can of radiator "stop-leak" in your cooling system... in an effort to stop a leak?? You might consider having your cooling system flushed, and put new anti-freeze in it. BUT, if someone has put stop-leak in the system in the past, your radiator will likely start leaking again as soon as you clean the gunk out the cooling system..

You may have air in the cooling system, the air bubble or gas bubble in the case of the head gasket leaking creates a block to circulation of the coolant. Google how to bleed the cooing system

Dear,

please get the Head gasket replaced of the engien as it seems to have leaked.

thanx

No there is not a place to put gas when you run out of it under the hood.. You are using a fuel injection system and you are thinking carbeurator... If you ran out of gas you will be able to get fuel pressure back in the fuel rails by turning key on and off.. but not in the crank position. You will hear the fuel pump priming.. just make sure that the fuel rails are full of fuel... and water mixing with oil?? if there is water mixing with oil in your system i will assume it is coolant.. and i will say head gasket. It is fairly expensive so if you know someone i would suggest to get them to do it... You can do a oil pressure test and see if your oil pressure is in spec.. and pressurizing the cooling system with a pressure guage to see if the cooling system holds pressure.. my guess is is that it wont

Thoroughly flush out the coolant expansion tank and cooling system, radiator , engine block ect... with a commercially available cooling system flush (Prestone or any other brand). Oil will damage the rubber cooling system hoses. Refill the cooling system with the correct amount of fresh antifreeze and drive the car after the cooling fans have cycled on and off. When the cooling system has cooled down top up as required and keep an eye on the cooling system for a few weeks to see if the problem reoccurs or if someone had inadvertently put oil in the reservoir.If not I'm more leaning toward a blown head gasket. it will run fine but you will have to keep the water clean out. to fix it buy a head gasket and surface the head..you have a blown head gasket

either you havent flushed the cooling system out properly ,or the oil cooler has packed up ,their is a oil cooler radiator of sorts that the oil filter screws onto ,these often leak ,just remove the water pipes and join them together with a small piece of copper pipe ,then if you see oil coming out of the water pipes fit a new cooler

If a mechanic putting the coolant back in after arepair didn't do it then the oil cooler connection in the raditor can fail but the head gasket can be leaking too. Check for coolant in the motor oil tooas his will tell about the head gasket. The oil isundermorepresure than the coolant except then the car is shut off after fully warmed. No coolant in the engine oil. Flush the cooling system real good and install just water run the car and look for oil again if it's clean then put new coolant in it and don't ley the last person to work on it since this happened to work on it any more as someone could have added oil to the coolant not knowing about cars well enough or trying to cause problems on purpose.

The oil you find your antifreeze is probably transmission fluid. This is when the trans cooler built into the radiator leaks internally.