My 2005 Volvo S60 has a problem of coolant water getting low. i filled up many times but after a drive, the coolant boils and flows out of the container through the cap.

 

Sounds like the Coolant Reservoir needs to be replaced.

 

You have a cooling issue. Few things could be your issue. 1st make sure your coolant fill cap is on tight , if not it won't allow proper PSI. Proper PSI prevents your coolant from boiling over as the PSI raises the boiling point. 2nd could be as simple as your coolant cap if the cap is bad it may release pressure to soon causing an over boil. 3rd check the cooling fan , if your fan does not come on you will over heat and cause a boil over. 4th hard to check, but a stuck thermostat can cause a car to over heat. 5th faulty or low flowing water pump. If the coolant is not flowing good your cooling system does not work like it should, most likely its not the pump though. I listed these in the order I would go about finding the problem, I like to check the easy things first until I find my problem. You may also want to pressure test your cooling system to see if its maintaining proper pressure.

 

When we had that issue I replaced the cap, the bottle, then the head gasket. It was a small head gasket leak, allowing combustion gases into the coolant passages.

 

Nice replies here above. I guess it resumes the checking list, and in order.

 

Rumor has it that you can get a test kit from an auto parts store to test your coolant for combustion gases.