Simple question. I bought some Red Line Water Wetter and want to add it to my S2 cooling system. I was thinking I’d add it directly to the radiator, rather than the bulkhead reservoir, to make sure it got circulated in the system. So I opened the petcock at the bottom of the radiator, drained a pint of coolant, only to find the fill neck at the top of the radiator still topped up. So… I think I’m stuck just adding it to the reservoir.