why do we NEED an expansion bottle?

[tillygti6]

not as stupid as it sounds really, most older cars dont run expansion bottles or big header tanks......

basically im wanting to use something larger in the rad department, but really dont want to run an expansion bottle if i can help it,
now a lot of jap stuff doesnt use bottles nor did all my old a-series stuff
so could i just plumb in a rad with its own small header and rad cap ?

ive got the option to aquire a nice ali rad off the ex missus evo4 (she does know lol)
just wondering the implications really....
would have put this in the track prep section but it wont let me yet.........
tommy

[atspeedracing]

usually if the radiator is not the highest point in the cooling system, then the expansion bottle will be placed higher up.

go back to a-series for example. the top of the rad is higher than the cylinder head, so did not use expansion bottle.

[tillygti6]

thanks atspeed!i was secretly hoping someone like yourself would answer, so thanks!
is that all it is then? obviously to stop potential airlocks and keep the system flowing. so if my rad cap is the highest point il be fine? how high up the head does the waterjacket flow as the standard rad doesnt exactly have much height? or am i missing the point completely?
tommy

[tillygti6]

anyone else have any opinions on this? :sweetheart:

[Gareth_R]

Once the system is bled of all air then as long as you keep the coolant topped up, no more air can get in. Thats why you have the expansion bottle on the side of the radiator. In order to properly bleed the system (on ax's, not sure about saxo's) you have to add height to the rad to get it to bleed properly

If you run a different kind of radiator to the standard one, with a header tank that you position higher up the bay, you no longer need to go through the process of selotaping an upsidedown bottle with the bottom cut off to the top of the rad and end up with it falling off halfway through

[tillygti6]

does anyone else run anything other than the standard rad? if so what? and how do you fill it?
tommy