I bypassed my core this summer and plugged everything up with a good rubber seal (plugs) to keep the air out and coolant in the core, to detour corrosion. Im also replacing the valve because it leaks slightly while I do this. It shouldn't be detrimental as long as eventualy (this winter perhaps) the flow of coolant returns. Johan 65 LeBaron Washington DC _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.