Why the car is overheating and when I check the raidator it overflowes and won't start until cools?

replace thermostat.then bleed coolant system, this is how you do it.fill the cooling coolant system with 50 / 50 dexcool and water to raise boiling point,straight water will evaporate boil away cause engine to overheat catch fire thats why you need 50 / 50 mixture antifreeze and water.to bleed coolant system first fill coolant system until coolant stay at the full cold mark on the the coolant overflow jug,then you start engine allow it to idle,place the heater and ac control in any ac setting except max and the temperature control to the highest setting,run engine until lower hose to water pump is hot. with the engine hot run the engine speed up to 3000 rpm and allow it return to idle, repeat this 5 times. slowly open the bleed valve on the thermostat housing or look for bleed valve at the water pump heater hose.open bleed valve for 15 seconds to expel any trapped air.then top off the coolant as necessary,and when top radiator hose hot thermostat open up.keep adding cooling to overflow until coolant level stop at full cold mark dont over fill coolant.if engine seem like overheating while looking at cooling gauge turn off engine wait a while until cool off add more coolant until coolant level stay stable and dont drop any.when open radiator overflow cap use large rag over the radiator cap to keep from getting scald open radiator cap a little at a time but dont open radiator cap until engine cool down first.replace the radiator overflow cap, thermostat,and engine coolant temperature sensor and check the cooling fans fuses and relays see what happens.

CHECK COOLANT LEVEL MOST NEWER VECHICLE DONT HAVE RADIATOR CAP YOU HAVE TO POUR COOLANT IN THE COOLANT OVERFLOW JUG THE COOLANT WILL GO TO RADIATOR. IF THE COOLANT OVERFLOW JUG EMPTY ADD COOLANT UNTIL COOLANT LEVEL STOP DROPPING AT STAY AT FULL COLD MARK.IF COOLANT OKAY,NEED TO REPLACE THERMOSTAT AND COOLANT OVERFLOW JUG PRESSURE CAP. IF ALL BEEN DONE. MOST OF THE TIME WHEN CAR OVERHEATING WHILE MOVING. RADIATOR CORES STOPPED UP OR RADIATOR GRILLE DIRTY OR RESRICTED.ENGINE BLOCK COOLANT PASSAGES CLOGGED AND HEATER CORE CLOGGED.CHECK WATER PUMP SEE IF WATER PUMP WEEP HOLE LEAKING IF SO REPLACE WATER PUMP.IF ENGINE OVERHEATING AT A LONG TRAFFIC LINE ENGINE COOLING FANS NOT RUNNING EITHER COOLING FANS FUSE AND RELAYS BAD.OR ENGINE COOLANT TEMPERATURE BAD. THE ENGINE COOLANT TEMPERATURE SENSOR TURNS ON COOLING FANS AT A CERTAIN TEMPERATURE IF SENSOR BAD FANS WONT TURN ON. MAKE SURE YOU HAVE 50 /50 MIXTURE OF COOLANT AND WATER IN COOLING SYSTEM.

YOU NEED BLEED AIR OUT THE COOLING SYSTEM.WAIT TO ENGINE COOL DOWN.YOUR VECHICLE YOU HAVE TO POUR COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STAY AT THE FULL COLD MARK.THEN START ENGINE LET IT IDLE A FEW MINUTES WATCH COOLANT IN THE OVERFLOW JUG WHEN IT DROPS ADD MORE COOLANT UNTIL COOLANT LEVEL STAY AT FULL COLD MARK.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW RADIATOR CAP BACK ON OVERFLOW JUG WATCH ENGINE COOLANT TEMPERATURE GAUGE AS COOLANT TEMPERATURE START CLIMBING TURN OFF ENGINE LET IT SET A WHILE KEEP FROM GETTING SCALDED.TAKE LARGE RAG PLACE OVER COOLANT OVERFLOW JUG CAP SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL PRESSURE RELEASE.REMOVE OVER FLOW JUG CAP.ADD MORE COOLANT UNTIL COOLANT LEVEL AT THE FUL COLD MARK ON THE OVERFLOW JUG.THEN SCREW CAP BACK ON THE OVERFLOW JUG.START ENGINE LET IT IDLE AGAIN WATCH ENGINE COOLANT TEMPERATURE GAUGE WHEN TEMPERATURE GAUGE START CLIMBING.TURN OFF ENGINE WAIT A WHILE.CHECK COOLANT LEVEL IN THE OVER FLOW JUG.DO THIS PROCEDURE UNTIL THE COOLANT LEVEL IN THE COOLANT OVERFLOW JUG STOP DROPPING AND STAY AT FULL COLD MARK,WHEN THE TOP RADIATOR HOSE GET HOT THERMOSTAT OPENING AIR IS OUT THE COOLANT SYSTEM. WHEN ENGINE COOLS DOWN.CHECK COOLANT OVERFLOW JUG COOLANT MUST BE IN THE COOLANT OVER FLOW JUG AT THE FULL COLD MARK WHEN ENGINE COLD. DONT .DONT OVERFILL COOLANT OVERFLOW JUG.KEEP COOLANT IN THE OVERFLOW JUG IF YOU LET COOLANT OVERFLOW JUG RUN DRY AIR WILL BE DRAW IN COOLANT SYSTEM CAUSE ENGINE TO OVERHEAT.

REPLACE THE THERMOSTAT AND RADIATOR PRESSURE CAP.IF COOLANT LOW, ADD MORE COOLANT THROUGH COOLANT OVERFLOW UNTIL COOLANT LEVEL IN THE COOLANT OVERFLOW STAY AT FULL COLD MARK.REASON POUR COOLANT THROUGH COOLANT OVERFLOW MOST GM CARS DONT HAVE RADIATOR CAP.WHEN YOU GET COOLANT LEVEL OKAY, CRANK CAR LET IT IDLE UNTIL ENGINE GET HOT BUILD UP PRESSURE THEN TURN OFF CAR.CHECK FOR COOLANTS LEAKS AT THE RADIATOR HOSES,CHECK FOR LEAKS AT THE RADIATOR, CHECK FOR LEAKS AT WATER PUMP WEEP HOLE IF YOU SEE COOLANT LEAKING FROM WEEP HOLE REPLACE WATER PUMP. IF CAR OVERHEATING WHILE IDLING YOUR COOLING FANS NOT WORKING CHECK COOLING FANS FUSE AND RELAYS.IF FUSE AND RELAYS OKAY THE ENGINECOOLANT TEMPERATURE SENSOR BAD.

ADD COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND COOLANT LEVEL STAY AT THE FULL COLD MARK.PLACE COOLANT OVERFLOW JUG CAP BACK ON JUG.CRANK VECHICLE UNTIL ENGINE START WARMING UP. STOP ENGINE WAIT FOR A WHILE UNTIL COOLANT COOL DOWN TO KEEP FROM GETTING SCALDED. USE A LARGE RAG OVER THE OVERFLOW JUG CAP OPEN OVERFLOW JUG CAP A LITTLE AT A TIME REMOVE OVERJUG CAP CHECK COOLANT LEVEL ADD MORE. COOLANT IN THE OVERFLOW JUG.THEN START VECHICLE AGAIN.LET ENGINE IDLE UNTIL TOP RADIATOR GET HOT.THEN THERMOSTAT WILL BE OPEN.WHILE ENGINE IDLING WATCH THE TEMPERATURE GAUGE IN VECHICLE IF TEMPERATURE GAUGE START CLIMBING IN THE HOT ZONE.TURN OFF VECHICLE LET IT SET A WHILE THEN USE LARGE RAG REMOVE OVERFLOW JUG CAP.ADD MORE COOLANT, PLACE CAP BACK ON START VECHICLE AGAIN KEEP DOING THIS PROCEDURE UNTIL TEMPERATURE STOP CLIMBING HOT ZONE.AND WHEN COOLANT LEVEL STOP DROPPING IN THE COOLANT OVERFLOW JUG.AIR IS OUT THE SYSTEM, BUT KEEP COOLANT LEVEL IN THE COOLANT OVERFLOW JUG AT THE FULL COLD MARK.DONT OVERFILL.DONT LET COOLANT OVERFLOW JUG RUN DRY IF SO AIR WILL ENTER COOLANT SYSTEM BECAUSE COOLANT LEVEL WILL BE LOW ENGINE WILL START OVERHEATING.

CAR OVERHEATING FIRST CHECK FOR LOW COOLANT IN THE RADIATOR COOLANT OVERFLOW JUG.IF COOLANT LEVEL IN OVERFLOW JUG LOW REFILL ADD COOLANT BACK TO THE FULL COLD MARK.PUT RADAITOR CAP ON COOLANT OVERFLOW JUG START ENGINE LET IT IDLE UNTIL IT OPERATING TEMPERATURE.MAKE SURE TOP RADIATOR HOSE GETTING HOT WHILE ENGINE WARM UP.IF TOP RADIATOR HOSE DONT GET HOT WHILE ENGINE IDLING YOUR THERMOSTAT COULD BE STUCK CLOSE CAUSING CAR TO OVERHEAT.IF TOP HOSE IS GETTING HOT.CHECK FOR COOLANT LEAKS CHECK TOP RADIATOR HOSE AND BOTTOM RADIATOR HOSE FOR LEAKS.CHECK FOR LEAKS AT THE RADIATOR CORES AND PLASTIC SIDE CONTAINERS.IF ALL IS GOOD ENGINE OVERHEATING WHILE IN A LONG TRAFFIC LINE, COOLANT FANS NOT COMING ON.COULD HAVE FAULTY ENGINE COOLANT TEMPERATURE SENSOR OR BLOWN COOLING FAN FUSE OR RELAY.COULD HAVE PCM FAULT.MAKE COOLING FAN ELECTRICAL CONNECTORS AND WIRING NOT DAMAGE OR BROKEN.

if its an overheating problem the cooling fans may not be coming on.this needs to be checked.it could also be a bad temperature sensor for the computer and its getting the wrong temp reading,thus not turning on the fans.there is also a cooling fan relay(not a problem that happens often).one other thing the impellers on the water pump may be worn out or not turning with the pump shaft.

Fill the water to the proper level with it cold. Start car and look inside overflow can. If as it warms up you see bubbles in the tank the chances are very good that you have a blown head gasket. Good luck and have a great day.

if you have a blown head gasket you would have a miss
the waterpump can look good and still be bad
after you replace the thermostate fill the radiator and leave the cap off start the car let it get too operating temp and check for flow if you have good flow shut the car off and and put a pressure terter on the raidator this will tell of and leaks

Remove the raidator cap while running or watch the overflow tank for bubbles. If you see bubbles either way, most likely your cause of the overheating is a leaking head gasket. If you have a cooling system pressure tester, pump up the cooling system and see if it looses pressure, if it doesn't hold pressure, again bad head gasket.