Since the weather has finally started getting warmer, the 6.2 in my '90 K5 has been running on the warm side and can get hot in a hurry when climbing long steep grades out on the trail. After draining the coolant I looked down into the radiator through the cap opening at there is a lot of the white colored corrosion/build-up along the edge of the core which is most likely the problem. I would like to try flushing it out before having to pull it out of the vehicle. Anybody have any good pointers are recommend any certain types of flush? The local auto parts store has some Preston brand flush that requires 3-6 hours of running and is intended for heavy buildup. I was planning on removing the thermostat to speed up circulation through the system and then trying to do a back flush of the system. If this doesn't work I might just get a new radiator. Anyplace, brand, ect...that you would recommend?