i just did it a month ago. I do it 2ce a year. in the fall and the spring time. But like i said no mech i've gone to can seem to find why they keep going. my entire coolant system is running perfect. pump, thermo, all hose or new. no leaks. the block isn't crack and no heads are warped. it's quite frustrating. i want a new engine totally so i don't have to deal with this anymore.