1998 Oldsmobile Aurora Surge Tank Drain

The correct way to drain your cooling system is to unscrew the drain plugs at the bottom of your radiator. This won't get all of the coolant out of the system, but it will get most.

Now having said that, you can also just use a suction bulb (the one used to siphon gas from your fuel tank) to suck the coolant from the surge tank until it is completely empty. There will still be a bunch of coolant in your system, but the level will be below the surge tank. Then loosen the hose that exits your surge tank and let the rest of the coolant drain into a pan. It will be messy. But you won't have to drain the entire system, nor replace all of that fluid.

Once you have the hose removed, you can then unbolt the surge tank and the fluid level sensor that's located at the bottom.