Building air in radiator and water disappears

Hello,

If you are having excess air, or air bubbles in your cooling system this can be remedied by making sure that when you fill the cooling system with coolant it is done from the highest point of the cooling system. For example; when I fill the cooling system on my vehicle, I take the top radiator hose off of the engine and hold it up so that it is higher than the engine and fill with coolant until I see the coolant running out of the engine where the upper radiator hose goes that I just took off and I know for certain that all of the air that might have trapped is expelled. My concern here with your vehicle is where is the coolant going. I hate to say this but this sounds to me like you might have a blown head gasket. This would account for the missing coolant and the excess air pressure, which would come from leaking compression into the water jacket. Here is a link below for you to go to to check to see if your vehicle head gasket(s) are blown or not:

https://www.2carpros.com/articles/head-gasket-blown-test

Please go through this guide and get back to us with what you are able to find out and we can go from there.

Thanks,
Alex
2CarPros

When the water started disappearing, i checked for the head gasket but the engine is clean neither the water is going into the transmission. There is no misfire too. Might be radiator cap. What is your suggestion for changing radiator cap?

I doubt it's the cap or there wouldn't be pressure in the system when you remove it, however it won't hurt to change it if you wish. What test did you do for the head gaskets? Any moisture in the carpet or near any hoses? That could cause a leak and then the system can make steam and cause a higher pressure. What coolant blend are you using?

it has been a year i bought the car and until now the power is same. There is no any sign of moisture nor any leak from any pipes. I am using 50/50. 50% coolant and 50% normal distilled water.

Many head gasket leaks will show no power loss, just coolant and unless it is a larger leak you won't see any steam or moisture in the exhaust either. The water loss started before you replaced the radiator and is still there so I doubt that being the issue. I would probably start with the pressure test mentioned in the guide above. A trick on that is to put the tester in place, then start the engine while watching the pressure gauge. If the pressure starts to rise rapidly as soon as you start the engine you have a bad head gasket. That would be the only way that pressure could be in the system that fast.