Cooling System Flush

You can flush the rusty coolant out of the engine permanently by the following steps. Before you start, you might want to source:

  • 5 or more gallons of distilled water
  • New thermostat and gasket
  • Acid based cooling system flush

  • Remove the thermostat. Careful, those bolts break easily so go gently. Put the housing back on without the thermostat. If it leaks a bit, that's ok.
  • Remove the upper radiator hose and divert it to the side.
  • Put a garden hose in the radiator inlet and turn it on so that water is overflowing out of the radiator.
  • Now, watch the hose coming from the thermostat. Run the water into the radiator until clear water emerges from the upper hose.
  • Remove the garden hose and reattach the upper hose.
  • Pour an acid based radiator flush in the radiator, there are many good ones out there, but it really needs to be an acid based flush.
  • Drive around for a while. (yeah, it takes a long time for it to heat up without a thermostat)(if the thermostat is leaking, don't drive too long)Hot acid flush is faster and does a more complete job.
  • Remove the lower radiator hose from the radiator and drain out as much as you can. Reinstall the lower hose.
  • Get a few gallons of distilled water. I find that 5 or 6 is enough for these small systems.
  • Remove the upper hose again and divert it to the side. Cover up the inlet with some tape. Remove the radiator cap.
  • Slowly pour 3-4 gallons of distilled water through the radiator cap fill neck and watch for the upper hose to have clean distilled water coming out. The system holds 1.5 gallons but you'll need a few gallons to flush the rust remover out.
  • Remove the lower hose and let as much clean water drain out as can. Reinstall the lower hose.
  • Clean the old gasket material from the thermostat tube and housing. Reinstall the thermostat using new gaskets. (I use a new 2 stage thermostat from OReillys).
  • Recheck all of the hoses to insure they are properly installed.
  • Add 1/2 gallon antifreeze for 33% or 3/4 gallon for 50% mix.
  • Top off with distilled water.
  • Drive the car until it gets up to temp and burp the radiator.
  • Top off with distilled water.
  • With the engine up to temperature, check for leaks around the thermostat and the hoses.