bubbles and pressure in water cooled system

[brad]

I supposedly have an aluminum radiator, but I am not so sure anymore. I have a waterblock that I know is aluminum because I made it myself. Well, after my watercooling setup has been off for a while, bubbles seem to build up in the radiator. There are no leaks anywhere in the system. The setup is completely closed and includes a water resevoir. When I opened the resevoir, lots of air and water flew out because pressure had built up somehow. I think something is reacting with the metals and creating a gas, which built up the pressure. Does this happen when there is copper and aluminum in the same system? Is there something that I can put in my water to prevent this? Thanks.

[jordan]

you can get water pump lubricant from the autoparts store or water wetter or purple ice from dangerden and becooling respectively, any of these three should nix the problem if it is indeed a reaction, also, are you using distilled water? If not, changeout your water with distilled water

[TechnoFile]

I've got a 'filler tube' in the top of my resevoir. Besides letting me tweak the mixture, it also lets me vent that pesky air out of the lines. There is always a little air in the top of the resevoir, but the water level stays high enough that it isn't a problem. I can plug the hose(if I decide to) by simply sticking a 3/8" bolt into the end of it.