Logo
FAQ

Project.
How to Bleed
the
Cooling System
(External Thermostat)

by
"Brian Burke" bburke@wowway.com

 

  Cooling System Bleeding

 

TO AVOID OVERHEATING CAUSED BY COOLING SYSTEM AIRLOCK,
PLEASE EMPLOY THE FOLLOWING PROCEDURE
WHEN REFILLING THE COOLING SYSTEM:

 

  1. Raise front of car and support safely on jack stands. It must be high enough so that the radiator filler neck is the highest point in the cooling system.

 

  1. Place heater temp lever in the ""heat"" position.

 

  1. At cylinder head tee (see Fig. 1) detach the hose that runs down to the thermostat.

  1. Loosen the same hose at the thermostat, but do not remove. Rotate the hose on the thermostat 180 degrees, forming a filler spout (see Fig. 2).

 

  1. Pour coolant into the hose until it begins to run out of the cylinder head tee.

 

  1. Replace the hose on the tee and tighten the clamps.

 

  1. Continue slowly filling the cooling system through the radiator until it is full, periodically squeezing the upper hose to force the air out.

 

  1. Leaving the radiator cap off, start the engine and allow it to run at around 1500 rpm until the lower radiator hose is very warm and the temperature gauge reads near the center of the scale. This indicates that the thermostat has opened.

 

  1. Bubbles may come out at the radiator neck.  Add coolant as needed.  If the radiator overflows, let it.  This is due to trapped air that is expanding.  The air will work its way through the system until it bubbles out the radiator neck.

 

  1. If everything is working right, the upper and lower radiator hoses should get hot.  The radiator fan should come on a little above 190F and shut off a little below 190F.  Let it cycle on and off a few times.

 

  1. Keep a close eye on the temperature gauge.  If things start getting too hot, shut it down and find and fix the problem. 

 

  1. While the engine is running, fill the overflow reservoir with coolant.

 

  1. If everything looks good, then top off the radiator and replace the radiator cap.  Shut off the engine and lower the car.

 

 

Congratulations, you are done!