Reverse flush Procedure Explanations

The best procedure for reverse flushing a vehicle cooling system is as follows:

  1. Add bottle of Inter-Ject Coolant Flusher directly into the cooling system by removing the radiator pressure cap.  Please note the cooling system might have to be partially drained prior to adding the additive to ensure entire bottle will be used.  (Be careful not to remove the cap when the vehicle is hot as it can spray hot coolant and cause severe burns).  Start vehicle and run for a minimum of 20 minutes.  If cooling system is extremely dirty you can leave it in the system overnight before flushing.
  2. The engine should be off and not running while flushing.  Make sure the engine is not too hot (not more than 180 degrees) as you do not want to flush a hot engine as it can cause engine damage.
  3. Remove the thermostat to ensure we get the proper flow through the entire engine and heater core.  If the thermostat were left in it would most likely be closed and would not allow fluid to flush through it.
  4. Once the thermostat is removed, reinstall the thermostat housing with no thermostat in it.  The coolant hose that would normally attach to the housing needs to be left off and pointed downward because this is where the old fluid and flushed water will be coming out of.
  5. Place a garden hose into the opening of the housing and position a rag around the hose to seal it.  Turn the water on as high as possible (the higher the pressure and flow the better).  The heater should be turned on to the “hot” position so that water can flow through the heater core. Now the flush water should be flowing out of the coolant hose that was previously attached to the thermostat housing.  This fluid is considered toxic and should be properly disposed of.
  6. If you have an air compressor available, position an air blow gun between the garden hose and the rag and squeeze the handle on the tool to force compressed air behind the water to give it a high pressure flush.  Please note that the flush water flowing out of the coolant hose will be blasting out like a high pressured fire hose.  Nothing will flush a cooling system better than this method, however be aware that it is very messy and you will probably get wet.
  7. Don’t forget to flush out the coolant overflow bottle also. This can be very dirty and holds a lot of debris. You can take the hose and place it in the bottle and turn the hose on to flush it out or you might have to remove the bottle to do a better job of cleaning.
  8. Once the flush water comes out clean and clear turn the water off and drain out as much as possible.  If you used the compressor then blow the air through the system to remove as much water as possible.
  9. Install the thermostat and gasket.  We recommend always installing a new thermostat and gasket as they are generally very inexpensive and you have already gone to the trouble of removing it.
  10. Install the Ve-Labs Coolant Filter in the inlet hose to the heater core. To remove any small particles that was left behind in flushing.  It will also reduce any pressure surges to the heater. (We do not recommend the filter in a vehicle with dual heaters)
  11. Add a bottle of Inter-Ject Electrolysis Arrester to the system.  Then refill and bleed system to manufacturer’s specifications with new antifreeze and distilled water.  Pre-mixed 50/50 antifreeze is best.DO NOT USE TAP WATER IT CONTAINS MENERALS WHICH WILL PROMOTE ELECTROLYSIS!
  12. Start vehicle and run until thermostat opens to ensure there is no trapped air in the system. Then pressure test system to ensure there are no leaks
  13. Install new Ve-Labs Rad Cap with sacrificial anode.

Shows debris left on the ground after flushing

Please see “Products” page for a more detailed explanation on Ve-Labs and Inter-Ject products.