Overflow bubbling

2002 SATURN SC2
245,515 MILES • 1.9L • 4 CYL • 2WD • AUTOMATIC
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CODYACK
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For some reason after driving my car just in town it gets a little hot, but every time i shut the car off the water is boiling in the reserve tank and comes out the overflow which it is not attached any where just hangs behind the engine and all the water comes out on the ground. why is this? someone help please.
Jun 11, 2017 at 4:29 PM
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SATURNTECH9
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You have a bad radiator cap and or the car is running too hot. Does the radiator fan come on when the temperature gauge is a little past the half way mark on the temperature gauge? Also, does the radiator fan come on with the A/C on?
Jun 12, 2017 at 12:40 PM
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CODYACK
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Yes it comes on then and not sure if it does when the A/C on.
Jun 12, 2017 at 12:44 PM
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SATURNTECH9
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The problem with that temperature gauge set up is there is only one sensor for the temperature gauge and to tell the computer the temperature of the engine. When the coolant temperature sensor goes bad they read colder coolant temperature then actual coolant temperature. So the radiator fan will not come on when it should and the temperature gauge will not show it is running too hot. Also, if you have a bad radiator and it is not holding the correct pressure it will let coolant come out of the cap even if it is not running too hot.
Jun 12, 2017 at 12:45 PM
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SATURNTECH9
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A bad radiator cap I was trying to saying not a bad radiator .
Jun 12, 2017 at 12:46 PM
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CODYACK
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My car does not have a radiator cap it just has the cap on the reserve tank.
Jun 12, 2017 at 12:46 PM
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CODYACK
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How can I fix this?
Jun 12, 2017 at 12:49 PM
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SATURNTECH9
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The cap on reserve tank as you call it is your coolant tank and it is under coolant pressure and the cap on it is your radiator cap. You can try replacing the radiator cap. Otherwise I would suspect a bad coolant temperature sensor which is pretty common for them to go bad on those cars. But to me it sounds more like a bad radiator cap.
Jun 12, 2017 at 12:52 PM
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SATURNTECH9
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The overflow bottles when cars have them are not directly tied into the cooling system and there not under pressure.
Jun 12, 2017 at 12:56 PM
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CODYACK
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Okay, the cooling fan does come on when I ran the A/C.
Jun 12, 2017 at 1:26 PM
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SATURNTECH9
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So I would start by replacing the radiator cap if it still leaks out the cap replace the coolant temperature sensor and inspect the inside of the connector if the terminals are green or blue instead of silver you will need to replace the connector as well.
Jun 12, 2017 at 7:52 PM