The purpose of the overflow bottle is to keep the header bottle full of coolant (no air). When the engine cools it draws coolant back in, not air. The other reason I use it is that with the metal bottle you can't see the level unless you remove the pressure cap when the engine is cool. Any generic plasic bottle works. I attached mine to a bolt on the left side of the engine compartment and ran a hose from the header bottle over the engine. The "trick" is that the hose must run from the tube under the pressure cap to the BOTTOM of the overflow bottle so it can pull the coolant back when the engine cools. The overflow bottle should also be as close to the same height as the header bottle. David Teitelbaum vin 10757 --- In dmcnews@xxxxxxxxxxxxxxx, "K. Creason" <dmc4687@xxxx> wrote: > >Install an overflow recovery bottle on the hose under the pressure cap. > > Interesting idea. Why? will it suck it back up if too low, or is it just to > keep it clean and earth friendly? > Do you know a small/perfect fit model number?