I have a 1993 Pontiac Sunbird, my radiator cap is spraying out coolant. Why?

First replace the cap, if that doesn't work take it to your local shop and have it checked for leaking head gasket. Compression getting into the water jacket will overpressurize the cooling system and the radiator cap will do it's intended job, and relieve the pressure as much as possible.

Been there done that.

dd

Make absolutely sure you replace the radiator cap with an AC Delco closed system radiator cap. The correct part # for this cap is listed in your glove compartment manual in the specification pages.

A closed system radiator cap has a large rubber gasket covering the inverted shell spring facing you as you look inside it. From your description the gasket is missing or the pressure rating is incorrect. Also, make sure the hose that run from the coolant recovery tank to the the small outlet at the top of the cap neck is free and clear. This allows the the radiator to push coolant back inside the reservoir when the pressure exceeds the pressure rating on top of the radiator cap. As the engine and cooling system looses heat when you turn off the motor a secondary check valve in the center of the radiator cap opens allowing the coolant to be pulled under vacuum back into the radiator, block and cylinder heads.

The whole plan of this system is to evacuate all air bubbles from the coolant making the system more efficient.

After replacing the radiator cap with a new one, there should be no coolant leaks when the engine is not overheating. If you have coolant leaks when the engine is operating normally, fix the leaks which can be in the radiator, hoses, water pump or anywhere in the coolant system. Make sure your coolant has been flushed and refilled with the proper coolant and the air bled from the system. It's assumed that you inserted the new thermostat like the old one came out and that it's not reversed in direction.

http://www.automedia.com/Keep_Your_Eye_on_the_Ther...

http://www.diynetwork.com/diy/ab_auto_cooling_syst...

http://www.aa1car.com/library/2004/cm60450.htm

http://www.aa1car.com/library/overheat.htm

Check the rad neck for a crack wipe clean but the cap on and make sure you push down and get it to all the way 2nd notch before you start this car check your oil if this is a blown head gasket some anti freeze may bleed into oil this will make the oil milky white and WILL lock up the engine if it looks this color or is overfull dont start car the thermostat will not fit in upside down and if it did it still opens at the same temp. If u dont see any of the above have a compression check done good luck.

When you put the radiator cap back on did you press down, I mean presss down hard and twist it all the way over in a clockwise direction.....the cap must be on tight to supress all the pressure from a radiator......if all else fails buy a new radiator cap - you might have a bad cap.....

check your engine and see if it overhead. it it does. than you need to check the fan. because sometime coolant spray because of engine overhead, other than that check the hoses, water pump. take it to mechanic if it get any worse. good luck.

replace your radiator cap, they are inexpensive and easy to replace. They do go bad...

either the cap is faulity or the rad neck is cracked

because it is a General Motors car. :)

Seriously though..take it in. I'm not sure.

YOU PROBABLY ONLY HAVE IT HALF WAY ON. GIVE IT A PUSH DOWN AND TWIST IT ANOTHER HALF TURN