So my Van has been slowly loosing coolant and I've been slowly tracking down potential problems but have yet to find the cause and was hoping for some thoughts. Last fall I went through and replaced most of the coolant and heating lines (all that I could tell were leaking plus some) including the upper and lower radiator hoses. Last winter I replaced the thermostat with an OEM one as well. I didn't have any problems over the winter, but as temps warmed up I noticed that when I would drive for more than an hour or so I'd start to loose coolant. The Van would continue to run at normal temps unless I didn't catch the coolant and fill it up regularly enough (like on cross country drives). Sometimes it would be loosing coolant through the overflow tank, but other times the overflow reservoir would would stay right in the normal range but when I opened the radiator cap I'd still have to add coolant. I figured maybe I had a pinhole in my radiator, but I just talked to my radiator shop this morning and he said that after washing and testing the radiator three times he still couldn't get it to leak at all. I'm going to flush the system while I have the radiator out, but at this point have run out of ideas for what could be causing the problem. I'm hoping the flush and cleaned radiator will help, but was wondering if there is anything else I should do or check while I have the system taken apart.Thanks,Dusty