I have a major over heating problem that just started up about a week ago. I replaced the water pump and low temp thermostat and finally the radiator. Filled with the correct fluids and let it come up to operating temp. Everything looked fine until I drove it down the road about 5 miles. The temp gauge kept climbing so I pulled over and let it cool. Here's the kicker... Sitting still and idling it cools back down to 150-160. Driving down the road...upwards to 240. Water has been drained 6-7 times and it still comes out brown rust color after running for a while. Do you think that the water ports in the block and/or heads are clogged? or limited flow? What is a good way to flush the block and heads without removing the heads? Is there a product that can clean the system? Any suggestions would be helpful. It's a 73 Mav 202
If you are not burping the air out after each fill up of the radiator, trapped air will still be in the engine, once it starts to circulate the steam will cause your temp gauge to rise very quickly, to answer your question, yes there are products designed for flushing the cooling system, you can get that and follow the directions listed on the label.
If you're sure it's full & didn't have a heating problem prior, I'd be sure the T-stat wasn't reversed and that the pump is OK... Maybe pump has a reverse rotation impeller??? Is the coolant circulating through the radiator as expected??? Upper hose getting hot when the stat opens??? If you're not sure it's full, pull the heater hose on intake and fill radiator till it comes out the open port...
when cleaning (flushing) the system, back flush...remove the heater hoses and back flush them. that way when you get the rad. clean you want gunk it back up when you turn the heater on. the new pump may have created more flow and washed the gunk out of the block.
One other thing to look at is the lower rad hose. Back in 2006 when I had the engine rebuilt I had the same problem. We couldn't figure out why it would idle at temp fine, but over head when driving. Turns out the old lower rad hose was collapsing when I was driving the car, at idle it was fine. I just happened to look down at the hose while revving the car and saw it suck shut. New hose fixed it... Also a spring in the old hose works too...
A good thought that does happen, it's why there is supposed to be a spring in the lower hose, but often they've rusted into pieces... May well have been OK until the hose was removed from old pump...
