I have a 99 S70 Turbo AWD with 99K+ Miles on it. Lately my low coolant light has been coming on. The first time when i checked the car, the coolant was low, so i filled it up to in between min and max with 50/50 coolant. Then a few days later the light came on again. So i checked to see if the car was leaking, but no leaks that i can see. i checked the hoses to and from the radiator and the coolant reservoir. So then i added coolant.
Then the other night, i got the light again and i pulled up to a gas station and popped my hood to add coolant. i slowly opened the coolant reservoir to let the pressure out slowly, then all of a sudden coolant came rushing back into the bottle fromt he return hose and the main hose.
I think this means my thermostat is broken or not working properly. But my car temp. guage has not indicated that the car is overheating.

So i am not sure if its the thermostat or something else.
Please help and thanks in advance.

 

Replace the thermostat and reevaluate. It's a cheap part.

 

I will do that and let you know. I got the part from autozone yesterday evening.

 

Ok. i Changed the thermostat yesterday evening. Not hard to do at all. The old one looked fine, but i put the new one in. I put back some coolant in the car. I let it warm up and looked for leaks. i could not find any. So then i went for a drive. When i came back. My coolant had gone down. But then i noticed my coolant bottle was dripping near by the hose on the bottom of the bottle. I tried to tighten the hose clamp and it started to leak more. i think this maybe where the leak is coming from the whole time.
I am going to loosen out the hose today or tomorrow, check it or cut hte tip and retighten it.

 

I would say you either have a pin hole leak and its evaporating as its coming out or your your heater core is bad. The cooling system is tied into the heater core. Turn your heater on and see if you smelll coolant....