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brandyv73's 1968 Firebird

2019 June
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Dan1

Grand Am Overheating

Question

Hello all, I'm the proud owner of a 1999 Pontiac Grand Am V6. Recently, the car has been experiencing a few issues that I can't figure out. For a while, the car would overheat and leak coolant whenever anyone tried to drive it. I noticed he radiator fans weren't coming on, so I replaced the two fan relays and that seemed to fix the problem. I also replaced the water pump, since it had begun to leak after the car overheated one day. The fans now come on, and the temp gauge stays right around 200 as usual. However, the coolant still boils over and the 'low coolant' light refuses to go away (even after I've just filled it). Why is the coolant still boiling over if the radiator fans work and the gauge reads normally? It doesn't seem like a thermostat issue to me? Please help!

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Have you replaced the radiator cap..???

If the cap is no good it will not allow the cooling system to pressurize and will boil over instead....( Very common overlooked problem)...Most the time you can't tell if the cap is bad by the way it looks....

As far as the low coolant light staying on when the system is full...It is more than likely the coolant level sensor ( located somewhere in the tank in the top of the radiator)..they're notorious for not reading the level correctly when they get some age on them...will have no adverse effect on the cooling system other than the light staying on... 

As far as the cooling fans the temperature sensors (thremal coupling) for the fans are designed to read liquid temperature not vapor or air temp...when the coolant level is real low and there is not enough water in the water jackets for the sensor to read.... The fans will not come on no matter how hot it gets.....(if everything is working properly the fans should come around 220 degrees with the secondary fan coming on around around 224 degrees) Also the fan should come on when the AC is turned on....No matter what the temp is.....

Edited by TWO LANE BLACK TOP

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Radiator cap seems correct for your issue. Also make sure to check your upper and lower intake manifold gaskets for leaking while you're at it. The cars are notorious for those going bad. 

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