Volvo: Volvo 850 s auto coolant, plastic tank, volvo 850

Question
HI,

My coolant seems to have fluid in it, but when i drive it, over heats, the water light comes on in the car, and then the pipes that connect to the coolant heading to the radiator pump air into the coolant

when i release the coolant lid/top, water quickly rises and pours out of the top and then the coolant basically empties?

any ideas what this could be?


thanks

Matt

Answer
there must be 50/50 mix of antifreeze to prevent boiling, otherwise it could be a faulty thermostat, siezed waterpump blocked radiator, blocked coolant passages in the engine, turn heat on to see if it blows hot air, before starting car there should be 50/50 mix in the whole system, if you have been adding just water this is a big no no, you must compensate by adding pure antifreeze , the coolant should be visible in the white plastic tank, if the heater blows hot air it is unlikely that anything is blocked and the water pump is turning.