95 cutlass supreme coolant circulates fine idleing than while driving loses heat and coolant goes in overflow

COOLANT LEVEL LOW---Check In Radiator, not in jug.

its time to change the head gaskets . DON'T drive it or you'll be putting in an entire engine

Check coolant level. As you increase rpms, coolant circulation increases, and vise versa.

hello anthony, several things could be causing your cutlass to overheat, The overall condition of your cooling system must be properly maintained for optimum cooling. The thermostat has to open fully at the correct temp. to allow coolant to be circulated through the block. Radiator fins, inside and must be clean and not restricted. The water pump and the fan clutch need to be fully operational. A clean mixture of 50/50 coolant to water filled to capacity is important. All cooling system hose in good shape and not kinked or restricted. Fan belts properly adjusted and not slipping---All this plays a part in keeping your engine running cool....If you haven't serviced your cooling system, i suggest you do so and replace the thermostat. I hope this information helps, good luck with your Cutlass.

coolant overflow tank low

This should not be a big deal. You can try a syphon tube but DO NOT SWALLOW ANY COOLANT. Or use a large turkey baster to **** up up coolant. It takes awhile though.
The car is fine to drive.

might not want to hear this but sounds like a head gasket,check the oil also if the oil is creamy like a light color this is probably the problem

Your engine is constantly warming and cooling. Your radiator cap has a set pressure release. As the pressure builds it allows coolant to flow out of the radiator into the makeup tank. As the engine cools it sucks coolant out of the makeup tank back into the radiator. If it overheats a lot then the makeup tank will overflow out of the overflow tube and it usually drips out under the car. If your radiator cap is bad or weak it can let coolant out when it shouldn't. This isn't a frequent problem but it can be a cause. The most likely cause is your thermostat is bad. The thermostat is closed when you start your engine and keeps the coolant inside of the block so it can't circulate through the radiator and cool until your engine is warmed up then at a set temperature (depending on thermostat), usually 195 degrees it starts to open and allow the coolant to circulate and cool. The thermostats can get bad and stick partial open or all the way closed and open. Yours is probably not functioning right and causing your makeup tank to overflow. When engine is cool look at makeup tank and you will see a minimum and maximum mark. Fill to maximum with coolant then start the car and let it warm up and monitor the coolant level and see if it is overflowing.

Your heater core has gone bad and needs to be replaced, If you go to Auto Zone you can pick up a new heater core and they will have the step by step instructions to doing the job yourself. If your lucky, may be the radiator hose to the heater core has failed at the cores pipes and it's only the hose that needs to be replaced but thinking not. You can get by pass the heater core for now so you can still get around till you pick up the new Heater core. Follow the two hose that goes to the fire wall and disconnect both of them from the pipe from the firewall, then with a pipe and two clamps, connect the two hose together and that's how you by pass the heater core. Good luck friend and hope this helps. 

Hello there.....

First things first: Is the temperature gauge showing normal as it is supposed to be? No contamination of oil & water on withdrawing the oil dipstick? Head gasket not the culprit here? No excessive steam on idling from the exhaust system? If these signs are not present than I suppose there could be an air lock within the cooling system - bleed the system - check if the radiator/coolant reservoir cap is satisfactory. Top up the radiator (if possible) with mixture of water & antifreeze whilst the vehicle is idling. Hope this helps.

Good luck