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I have a 97 Saturn SL2. My car was overheating, temp gauge does not get hot. So the fan never goes on Why
The car overheats so much the water is coming out of the overflow bottle cap. The temperature never goes higher than the center. And the fan never comes on, at all. Could it be a sensor? The water pump? Thermostat? Do I need a new radiator? What?

there's a serpentine belt driving the power steering, alternator and water pump. If you may be able to turn the wheel, your water pump is working.

The fan does not come on, because you have overheated the car usually enough there is not much coolant left in the system.

The root because is the thermostat. Change the thermostat, put on a new radiator cap, flush the radiator, and install non phosphorous long life coolant.

I used to be a GM engineer before I defected to Chrysler.

I could say it's the thermostat.

Yes, it may be any of them. 1st, I'd do the radiator cap, or coolant fill cap, as they're supposed to hold pressure. Next, I'd get the cooling fan tested, to be sure its not bad. If its good, then check your hoses to see if they're in good condition. Then also you may want to check the thermostat, and be sure its working properly. Also be sure there's a belt driving the waterpump. Sounds silly, but maybe could happen. Hope these help a bit.

check your thermostat, if that does not work, be sure your temp sensor wire is connected and of course that the fan relay is working. if the car is sluggish or running rough, it may be your head gasket or clogged radiator.i do not think water pump because you could have water leaking from the pump area

It may be that the fan is broken or maybe the thermostat isn't working so isn't sending the signal to the computer when the engine is to get hot to begin the fan.
Take care of that ASAP because remember that could damage the engine.

If your guage is reading cool.and your fan is activated by the guage.your guage / sensor can be bad..if the fan has it is own sensor.then it can be bad also.not common.if it WAS the thermostat.the guage should read hot..check your anti freeze/ anti boil mixture.should be @ 50 / 50 mix W distilled water ..any other mix will rely on weather where you're.tester is available for @ $5.00 at any auto parts store.good luck

air is trapped inside the engine follow Saturn information for coolant bleading there may this brass bleader some where on the engine to let the air out or small hose at the top of the engine you have to take off to let the air out of the cooling system, OH YES it's overheating inside the engine block the boiling over but the air around the water temp sender isn't reading real coolant temp just 230 degree air or normal operating temp. that's why the fan sensor is being fooled too. generally use correct coolant mixture 50/50 water blended in orange or green see holders manual dexcool orange color or glycol green.

before spending money do both radiator hoses get hot? if not coolant isn't flowing. thermostat or plugged radiator. if both hoses get hot ouch to touch
go to a parts store and ask for a block check kit. I know NAPA carries them. lower radiator about a half gallon or so we do not want it to spout. remove rad. cap and take block check has a tappered stopper and fill it to the line with blue solution and cram it in the radiator. start cold engine and let it to warm up if the blue solution turns green or yellow exhast gasses are present in coolant. blown head gasket or cracked head is probably. if you're low enough on coolant that air is present inside engine temp sensor may not really be to get touched by hot coolant hence false reading. also if you overheated bad sensor may failed. sensor is a wax pellet inside if brass case stretches throughout really bad overheat sensor will never be correct again and needs to be replaced.the block check tester is cheap in comparison to spending money on a whim.

the water pump is chain driven, its possible that the chain broke and the water pump is turning... beleive me it drove me nuts