Replaced water pump, alternator, radiator, crank sensor and no coolant leaks and car has antifreeze, but why is low coolant dashboard indicator light keep flashing on 97 saturn sl2

the plastic jug is an overflow container when the vehicle gets warm excess coolant from the radiator flows to it there is a sensor somewhere on the jug or in it for coolant level if it doesnt hold coolant it is most likely cracked as it is only plastic and should be replaced

SOUND LIKE BAD WATER PUMP.IF BATTERY LOW CHARGE LIGHT ON WATER PUMP BEARING COULD BE LOCKING UP DRAGGING DRIVE BELT DOWN ENOUGH TO SLOW DOWN ALTERNATOR TO KEEP BATTERY FROM CHARGING.REPLACE WATER PUMP AND THERMOSTAT.CHECK COOLANT LEVEL SEE IF ANTIFREEZE IN RADIATOR IS LOW. IF SO FILL COOLANT SYSTEM BACK TO NORMAL LEVEL SEE IF WATER PUMP WEEP HOLE LEAKING WHILE ENGINE RUNNING IF SO WATER PUMP IS BAD.

IF YOU GOT TOO MUCH WATER IN COOLANT SYSTEM AND DONT HAVE 50 / 50 MIXTURE OF ANTIFREEZE AND WATER. WATER WILL EVAPORATE BOIL AWAY.CHECK FOR COOLANT LEAKS LOOK AT TOP AND BOTTOM RADIATOR HOSES LEAKS, CHECK FOR COOLANT LEAKS AROUND BOTH RADIATOR CONTAINER AND RADIATOR CORES LEAKING. CHECK WATER PUMP WEEP HOLE. IF LEAKING WATER NEED REPLACING, CHECK ENGINE CRANKCASE ANTIFREEZE WILL LEAK IN CRANK CASE OR LEAK IN THE INTAKE GASKET COOLANT WILL BURN WITH FUEL.MANY THINGS WILL CAUSE COOLANT LOST.

OVERHEATING CAN BE CAUSE BY MANY THINGS LIKE FAULTY THERMOSTAT AND FAULTY RADIATOR PRESSURE CAP,TOO MUCH WATER IN COOLANT SYSTEM NEED 50 / 50 WATER AND ANTIFREEZE.LOOK FOR WATER PUMP WEEP HOLE LEAK, IF COOLANT LEAKING OUT WEEP HOLE WATER PUMP BAD NEED REPLACING.CHECK FOR LOW COOLANT LEVEL, YOUR RADIATOR OVERFLOW JUG SHOULD HAVE COOLANT AT THE FULL COLD MARK IF NOT KEEP ADDING COOLANT INTO COOLANT OVERFLOW JUG UNTIL COOLANT STOP DROPPING AND FULL COLD MARK, IF OVERFLOW COOLANT JUG WAS EMPTY RADIATOR IS LOW ON COOLANT.WHICH CAUSE AIR IN COOLANT SYSTEM KEEPING THE ENGINE COOLANT TEMPERATURE SENSOR FROM BEING SUBMERGE IN HOT COOLANT WHICH TURN ON THE COOLANT FANS.WHEN ENGINE COOLANT TEMPERATURE GET CERTAIN SET TEMPERATURE LIKE 190 DEGREES THE PCM AND COOLANT SENSOR WILL TURN ON COOLANT FANS, IF VECHICLE OVERHEATING COOLANT FANS NOT WORKING EITHER YOU HAVE FAULTY ENGINE COOLANT TEMPERATURE SENSOR CHECK COOLANT FANS FUSE AND RELAYS. YOU CAN CODE SCAN CAR TO SEE IF YOU HAVE FAULTY PCM, FAULTY ENGINE COOLANT TEMPERATURE SENSOR OR FAULTY COOLANT FAN RELAY.IF COOLANT FAN AND ENGINE COOLANT TEMPERATURE SENSOR OKAY,YOU HAVE CORRECT COOLANT LEVEL IN COOLANT SYSTEM, THERMOSTAT AND RADIATOR PRESSURE CAP BEEN REPLACED, YOU COULD HAVE BLOWN HEAD GASKET CHECK ENGINE OIL LOOKS LIKE MILK SHAKE HEAD GASKET BLOWED ALSO WHEN HEAD GASKET BLOWED YOU CAN DRIVE CAR SHORT DISTANCE START OVERHEATING AND YOU LOOSE ENGINE POWER SUSPECT BLOWED HEAD GASKET.

The most likely causes of a hot running engine are the following:

1. low antifreeze level in the radiator and cooling system.
2. fan not turning on at operating temperature.
3. restrictions in the cooling system such as sediment build up.

Water pumps usually leak when they are bad, and can cause an overheat because of low coolant level.
Check whether the water pump is leaking after topping off the coolant level and running at operating temperature, and then shutting off the car's engine.

You probably have air pockets in your cooling system. I have fixed a few of them by removing the Coolant Temperature Sensor just behind the Thermostat Housing. They can be kind of hard to get to on 3.3L Engines. Anyway, remove the sensor and pour antifreeze into the radiator until antifreeze pours freely out of the sensor hole. Then re-install the sensor. You may have to top-off the radiator after the sensor is re-installed.

If this does not fix the problem the you could have a bad water pump. Sometimes the stamped-steel impeller on the water pump gets corroded to the point where it cannot circulate the coolant properly.

it could easily be burning the antifreeze through a bad head gasket. if when warmed up the upper hose is quite stiff indicating the system is under pressureand you shut it off,even waiting until the radiator fan comes on and then right away turning of the key,wait and see iff anything runs out.the water pump would have to be looked at from below while the leak is ocuuring= reason must mechanics suffer a lot of burns. or with a sall extendable saft mirror. you could also loose antifreeze from a heater core leak but that would give a lot of steam on your windshield inside in the cold weather,or the carpet would be wet inside the car

SOUND LIKE RADIATOR HOSES AND RADIATOR.ONLY WAY TO CHECK IS FILL UP RADIATOR WITH COOLANT.CRANK UP CAR UNTIL WARMS UP.LET RADIATOR PRESSURE BUILD UP.THEN TURN OFF CAR.LOOK FOR WATER LEAKS AT RADIATOR HOSES AND AROUND THE RADIATOR.

CHECK ANTIFREEZE IN RADIATOR.IF LOW ADD COOLANT.CHECK FOR LEAKING RADIATOR HOSES AND WATER PUMP HOSE.ALSO CHECK RADIATOR FOR LEAKS.IF ALL GOOD NO RADIATOR LEAKS.REPLACE THERMOSTAT.IF STILL OVER HEATS AFTER REPLACING THERMOSTAT .CHECK COOLING FANS FOR OPERATION AND COOLANT SENSOR.ALSO CHECK TO MAKE SURE WATER PUMP WEEP HOLES IS NOT LEAKING.BECAUSE A BAD WATER PUMP CAUSES OVERHEATING ALSO.

1 Inspect Oil Pan Gasket - Performance Ruptured, cracked or leaking radiator hose. 2 Inspect Hose (Bypass) Ruptured, cracked or leaking bypass hose. 3 Inspect Hose (Heater) Ruptured, cracked or leaking heater hose. 4 Inspect Radiator Cap Worn or damaged radiator cap 5 Inspect Heater Core Heater core may be leaking antifreeze/coolant into the vehicle`s floor area. 6 Inspect Heater Control Valve Leaking or defective heater control valve. 7 Inspect Radiator Drain Plug Loose, damaged, or faulty radiator drain plug. 8 Inspect Radiator Rusted, corroded, or damaged radiator may be leaking antifreeze/coolant 9 Inspect Water Pump Damaged, worn or leaking water pump. 10 Inspect Cooling System Mix Coolant level low or flow is restricted. 11 Inspect Head Gasket - Performance Blown head gasket 12 Inspect Hood Brace Leaking, worn, or damaged intake manifold gasket 13 Inspect Freeze Plug Freeze plugs are cracked or leaking.