We actually do an engine flush every 1000hrs. along with the timing belt and water pump change, so we don't damage the new water pump bearing. Water pump failure would be very bad for these engines. We don't use vinegar but a acid cleaner used in restaurants to dissolve lime build up. What you use depends on the minerals that are building up. Yes we have lost engines due to lime blockage in the water jacket. Some areas to check for build up--thermostat, is the sensor covered with a white substance that you can chip away?(we clean the thermostat every year)--drain plugs, do you have to pock a hole through a membrane for water to run out? are there 'flakes' in the water that is draining from the block and manifolds? Places that block up first on the Toyotas are the oil cooler, remove both hoses and try to run water through, and around the throttle body, the thermostat on the bottom of throttle body gets plugged, also if you use a heater these veins will clog . This build up will only occur where water is being heated.
Hope the vinegar works(be careful of the water pump bearing) , I would rather not use the cleaner but have no choice because the ports would be plugged after 1200-1500 hrs. Good luck Joel
