[astikhossw]

You can put about a gallon of cleaning vinegar in the radiator and let it circulate for 5 or so minutes and let it sit over night and then water hose it out then fill the system with fresh water and circulate that for 5 or so minutes and dump it. It will clean out the rust and scale in the block and radiator, you just to flush it ienough to get the water back neutral.