You have air in the lines. Let the car cool and remove the radiator cap. Turn heat all the way to hot. Run car till it reaches operating temperature. Top off fluid. Look for foam in the coolant as that is sign of air in system.
Put cap on and drive car. With car running still, loosen the system bleed screw slowly and if fluid comes out in good stream, the air is gone. If not let the car cool and repeat procedure. If it happens again klet car cool and add coolant put cap on and bleed screw and continue to run and loosen bleed screw until it runs out in steady stream.
If this does not work then the leak sealant might have clogged something.
Monday, March 5th, 2012 AT 2:12 AM