I'm not positive here, but I think you would need to change the radiator cap. With an overflow bottle the cap must seal on expansion to the desired setting and then allow the coolant to siphon back when cooling. I don't think that pre-overflow bag/botttle caps had this feature. They just sealed tight. You should fill themradiator full. the ottle is the expansion area. 4 - Toes On Sun, 14 Apr 2002 14:49:48 +0000 tntlucat@xxxxxxx writes: > Hey Bill, > An overflow should work, in theory. As your coolant heats > up it expands and will find any escape route,like your > drain tube to the street. If that drain tube went into a > reservoir it would keep all the environmentalists > happy first, and second as it cools it should siphon the > overflow back into the radiator. Try maintaining the > level of your coolant about an inch or two from the > bottom of the radiator fill neck when the motor is cold > to minimize overflow. Also check to see what the > recommended pressure rating of your radiator cap is for > your specific motor. The purpose of the radiator cap is > to control the boiling point of the coolant/water mix by > keeping it under pressure. Hence "NEVER OPEN WHEN HOT!" > If this condition persists you may want to replace your > thermostat. If it is defective, i.e. stuck open or > closed, the circulation and cooling effect through the > motor will be greatly compromised. > Good Luck > T.L.