Overheating fan will not run ! I change cooling sensor, fan relay,new radiator, thermostat, fan motor, check all fuses, tank low coolint sensor, put fresh coolant in also. (1998 achieva SL 3100 V6 SFI ) The only time i get fan to run is when i pull connector off cooling sensor. change this sensor twice to be shure. sensor has voltage on it about 5 v bench test fan also works fine. When coolint sensor is disconected the fan will run and keep running until i connect it back to sensor then it shuts off. Guage in car reads pass the half way mark and engine get pretty hot at this point and starting to steam and our boil over. At this point i shut engine down in fear of brusting something everything is new. HELP I RAN OUT OF PARTS THANKS !

Check and see if the cooling fans are coming on. Check fuses and relays for them.

check fans --cooling sensor --relays--check oil for coolant possible intake or head gasket leak

Only overheating at idle while standing still is most probably a cooling fan problem. If you have the electrical cooling fan, then first check its fuse. If ok, than there are two separate relays (high speed and low speed) in the power distribution center under the hood. (this is for 2004 model only). Swap both relays, it can be that the low speed relay is bad. If this helped, than you will have to replace the bad relay. If this didn´t help, then put 12V directly on the fan motor (watch hands and loose clothing) to be sure the motor is not bad.

first check coolant level in radiator coolant level sound low.if coolant overflow jug empty.coolant sysyem low, when add coolant to coolant overflow jug coolant level should stay at full cold mark.if coolant level okay,engine overheat while sitting or moving in slow traffic either coolant fan relay or fuse could be bad.or engine coolant temperature sensor could be bad. coolant sensor turn on cooling fan at certain temperature.hot wire check to make sure cooling fan motor not bad or short in wires.if all is good have pcm check it controls fan relay to through the coolant temperature sensor signal when coolant get hot.

OVERHEATING CAN BE CAUSED BY LOW COOLANT,TOU COULD HAVE TOO MUCH WATER IN COOLANT SYSTEM YOU NEED 50/ 50 MIXTURE OF ANTIFREEZE AND WATER TO RAISE BOILING POINT.IF COOLANT OKAY, IF VECHICLE OVERHEATING DURING SHORT DRIVE COULD HAVE BAD THERMOSTAT AND FAULTY RADIATOR PRESSURE COOLANT CAP. IF THERMOSTAT OKAY CHECK WATER PUMP IF WATER PUMP WEEP HOLE LEAKING.YOU NEED NEW WATER PUMP.IF VECHICLE OVERHEATING WHILE VECHICLE SITTING IN A LONG TRAFFIC LINE.CHECK TO SEE IF COOLANT FANS RUNNING IF NOT CHECK COOLING FANS FUSE AND RELAYS.IF ALL IS GOOD. YOU COULD HAVE ENGINE COOLANT TEMPERATURE SENSOR CODE SCAN FOR FAULTY PCM. HOT WIRE TO SEE IF COOLANT FANS WORK IF NO FAN MOTOR BAD IF YES COOLANT FANS WHEN HOT WIRED. FAULT COULD BE IN THE COOLANT FANS WIRES MAKE COOLANT FANS RECEIVING POWER IF NOT YOU HAVE BLOWED FUSE OR BAD RELAYS.

FIRST OF ALL I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP THEN CHECK SEE IF COOLING FAN RUNNING.WHILE CAR OVERHEATING. IF NOT CHECK COOLING FAN FUSE AND RELAY.IF ALL IS GOOD THE ENGINE COOLANT TEMPERATURE SENSOR COULD BE FAULTY.HOT WIRE SEE COOLANT FAN WORKS IF NOT, COOLING FAN MOTOR BAD NEED REPLACING.IF COOLING FAN MOTOR WORKING PROBLEM COULD BE IN FAN MOTOR WIRING OR PCM FAILED.

WHEN CAR STARTING OVERHEATING MAKE SURE COOLANT LEVEL DIDNT GET TOO LOW. IF NOT I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP IF OVERHEATING WHILE SITTING IDLING COOLING FAN NOT COMING ON.CHECK COOLING FAN FUSE AND RELAY IF ALL IS GOOD.CHECK COOLING BY HOTWIRING IT.IF RUNS YOU HAVE A BAD COOLANT TEMPERATURE SENSOR OR FAULT IN WIRE CIRCUIT.IF FAN DONT RUN WHEN HOTWIRED REPLACE FAN MOTOR.IF CAR STILL KEEP OVERHEATING CHECK ENGINE OIL LOOKS LIKE MILK BLOWN HEAD GASKET.IF OIL LOOKS OKAY YOU NEED RADIATOR AND ENGINE FLUSHED OUT.

SOUND LIKE COOLING FANS NOT RUNNING CHECK AND SEE DOES COOLING FANS TURN ON WHEN ENGINE OVERHEATS IF NOT CHECK COOLING FANS FUSE AND RELAY IF BOTH CHECKS OUT GOOD HOT WIRE COOLING FAN.IF IT WORKS.PROBLEM COULD BE COOLANT TEMPERATURE SENSOR- PCM- AND OPEN OR SHORT IN WIRES.IF COOLING FAN DONT WORK WHEN YOU HOT WIRE IT PROBLEMS THE FAN MOTOR.

check the hoses, check the radiator, check the fan, fuse and relays, check the thermostat. check to make sure the head gasket is good, by check for oil and water mixture on the dipstick, same will appears brown

If the cooling fans do come on, replace the radiator. It has probably plugged with deposits from coolant that has not been changed every 2 years as recommended. Radiators.com has real good (low) prices and excellent quality all metal radiators--do not get 'plastic tank' unit.

IF the fans are not turning on, it is either the temperature sensor for the cooling fans, the relay, the fuse, or the fan motor-or a loose connection in those circuits.