is it normal to have both tanks to be only half full every time i check the coolent in the morning? its like its not sucking back in the coolent but its not blocked and the spring thing works as there is slugy brown stuff underneath it every morning.

 

Since you said "both tanks" I am assuming you have an FD and these are the overflow jug and the AST? The AST should stay full and after the car cools the overflow should stay at whatever level you have filled it to.

If the AST won't stay full then coolant is being consumed or it is not sucking back during cool down vacuum. Recently went through this. Mine turned out to be the flat cap not sealing. It wasn't leaking coolant but would leak air pressure and vacuum causing no return from the overflow jug. The flat cap is the coolant cap on the engine.

Check pressure cap with tester or replace - they are cheap.

Clean overflow jug. Mine had some green gel in the bottom. Clogging up the tube.

Check flat cap. When you put it on put some coolant around the seal with your finger to help it seal. After driving and cooling down remove it. If it is sealing well it will sort of stick on there even after the locking ears are disengaged and you will have to pull it off. If not try a new one.

 

Thanks heaps ai, I thought it was that. It makes sense if you haven’t got a closed system then the energy inside that system isn’t conserved lol. I.e. the vac and pressure meet equilibrium.
from the slugy brown stuff i saw underneath the cap with the spring valve in it slike it dosent seal prop when it shuts and thats how the slugy brown stuff builds up. one of my theorys lol.

 

I'm not entirely clear what you are asking but check out the 3rd gen FAQ thread stickied here and in the 3rd gen forum and read the links on the cooling system. Pretty much all you need to know about the cooling system is in there.