1997 CHEVY EXPRESS CONVERSION VAN 5.7 ENGINE MARK III VAN OVERHEATED AND THEN I HEARD A KNOCK IN THE ENGINE. I GOT THE VAN HOME THE RADIATOR WATER WAS RED IN COLOR. AFTER IT COOLED DOWN I CHANGED THE WATER AND IT DIDNT OVERHEAT NO MORE BUT NOW I HAVE A KNOCK IN MY ENGINE ,,,,,,, HELP ( CHANGED THE KNOCK SENSOR LAST NITE)

SOURCE: 91 SL1 problem

the sensor is located at the rear side of cylinder head between transmission and engine under the thermostat hosing but make sure to have some one aply direct power to fan to se if fan still goos if not replace it, and the sensor all what you have to do to test it start the car unplug the sensor and if the fan come on then replace the sensor i will recomend to replace thermostat also and make sure is full of coolant

SOURCE: car overheats. have replaced radiator,thermostat.water

Question that I pose is:
Is the car overheating or are you assuming it is as the gauge is telling you that it is?
There are two cheap and simple things that are not mentioned in this post. There is an Engine coolant temp sensor which in all of their innane wisdom Saturn built with a plastic tip and we all know plastic melts fairly easily. This part is a simple fix as it needs a 13mm deep socket and that is it for tools to replace it and it is $10 - $15 for a new on with a copper tip. There is also an Engine coolant temp switch which sends information to the PCM to tell the gauge what the reading should be. Aslo $10 - $15 and a 13MM deep socket to replace. These are common issues with the S Series Saturns. I do however recomend that if you are going to replace them yourself that you empty the radiator of coolant as the sensor and switch are directly in the engine block coolant flow and will give you a nice little shower if you do not at least jack the drivers side up before replacing them.

SOURCE: overheating engine

Check your freon level on your AC system. If unit is low, it can actually put out more heat in front of the radiator. Does it overheat when the AC is off?

SOURCE: 95 honda civic lx overheating

COULD BE COOLANT SENSOR,HEAD GASKET,CHECK THE TIMING,THE PROPER MIXTURE OF COOLANT,WATER PUMP.DID YOU HAVE IT CHECKED OUT?ANY LEAKS?HEAT WORK WITH FAN?

SOURCE: overheating on stop and go traffic

I had the same problem on my SL1 2002 and my wifes SL2 2001. In both cases, the electric radiator fan motor needed replacing. It was not difficult but took me a full day of trying to figure out how to pull the plastic housing it is mounted in. Someone who knows what they are doing could have changed it in a half hour. Works great now.