Thanks for all your inputs. I did a compression test 2 weeks ago and came back around 150 on all 4 cylinders. I'v just flushed and empited out the radiator and looking down inside the rad, the fins are covered with that gunk. I'v added toyota red mix inside. Im waiting for a new rad cap to see if it resolves this lift of coolant up the expansion tank, and it dont syphon back into the radiator when cools down ! . (It started overflowing when it was on the rollers)