cooling problems

[deaf_rattle]

after a bit of a drive The overflow bottle keeps getting filled up and then once its full it pours out of the pverflow bottle.
why does it do this and how do i prevent it?

cheers

[fangsport]

is there air bubbles in the header tank of the radiator?

get a compression check, you could have a blown head gasket or a blocked radiator.

[JasonZE]

If you think about it for a minute you will realize there is only one way it can get water in there and thats via the radiator cap.
Replace the cap or get it tested and check the neck of the radiator as any build up or sometimes even an old seal from an old cap can be stuck in there.
If it continues with a new cap then the cooling system is over pressurising due to overheating (thermostat/fan fault) or blown head gasket causing combustion to enter the system and building up pressure.
But 9 times out of 10 its just a faulty cap that causes the bottle to overflow.

[deaf_rattle]

replaced cap, still does it.
Head gasket is fine i believe (no signs of a bhg anyway)
might have to get a new radiator i think, this one might be on its way out.

[fangsport]

does it appear to be flowing freely trough the radiator?

[JasonZE]

Is the temperature normal?

What cae is this in did you get the right cap for it there are quite a few different caps for japanese cars and from the top they all look the same but have different lengths and seal configurations as well as pressures ie 0.9,1.1 etc
Take it to a radiator shop most will check radiator and cap for free and give good advise
If its not overheating the cap cant be sealing so look further into it.

[RAZA]

im sure you've already taken this into account but how full are you filling the overflow bottle?
cause what you described will always happen a bit as water expands when it gets hot.

and if you've got your original overflow bottle and your new engine holds more water than your old engine that could be it.

as long as the water is returning through the radiator cap into the radiator when your engine cools down and theres no sign of gas / bubbles in the radiator then thats probably all it is.