I HAVE A 2000 ALERO.. MY HEATER IS NOT WORKING AND MY CAR IS OVER HEATING.. WHEN MY CAR IS COLD AND I FILL IT WITH WATER, WITH THE CAP OFF, I THEN TURN MY CAR ON AND THE WATER DOES NOT PUMP UP AND THEN I PUT MY HAND OVER THE COVER AND I DO NOT FILL THE PRESSURE OF THE PUMP WORKING... WOULD THAT BE MY WATER PUMP NOT WORKING OR MY THERMOSTAT? OR BOTH?...BUT WHY IS MY HEATER NOT WORKING AS WELL???

Turn the heat control to max and remove radiator cap - add coolant as much as possible. Make sure overflow container is filled to correct level - then Start car and run - after the thermostat opens water level may go down some - keep adding coolant till it is totally full. Turn engine off and put radiator cap back on tight.

-Make sure the radiator is full of coolant (water) ?
A: No. fill it then try again.
Yes it's full.
-Check the heater valve is working or not (When slide from cold to hot)
or hot to cold the valve shold turn. If not the cable is broken or unhook.
Yes the valve is working but still no heat.
-The heater hose is clog. Disconnect both heater hose (Inlet & outlet) from the engine and flush w/garden water hose from both direction for coulpe minuites
**This will flush from the one end to the heater core and out at the other end .
-Reconnect all hose then fill radiator to full. run the car, turn on heater in hight. You should be good to go.


Mai Lor

I've had this problem. 2000 GMC uses a closed coolant system. Meaning takes and returns coolant from and to the Reserve Bottle and has little air in the engine and heater systems.
If everything appears ok but no heat. "Air Lock" is the most likely cause. (With interior heater set to full heat) Solution; 1. Make sure water pump works. 2. Drain about 1/2 engine coolant into container. 3 Remove both heater hoses from engine side and flush heater core in both directs through heater hoses with garden hose. 4. Reattach heater hoses in correct locations. 4. Refill engine with coolant. 5 Start engine and run for 2 min., use caution when topping up coolant.
6. Most 2000 GMC have twist off caps with plugs located mid way on heater hoses. with engine cold, start engine these caps may be loosened to allow trapped air to escape. Do not attempt with engine hot due to hot coolant injuries. This may take more than one attempt to remove all air from heat system. 7. Lastly most 2000 GMC water pumps have a bleeder plug,( 3/8" square driver plug) located on the water pump. With egine cold this plug should be removed to remove any air. Reinstall plug with thread sealant.
Hope this helps cheers

You did not BLEED the radiator and it's over heating.

Take off radiator cap when engine is COLD

Start engine

Let it idle until it's HOT

As it heats up you will notice air bubbles coming out of the radiator filler neck.

Let car run until you don't see any more bubbles

Fill radiator coolant to keep it topped up to the hot mark.

Put radiator cap back on once you hear the fans kick on.

Done

You should now have tons of heat

Providing your water pump is working

TAKE RADIATOR CAP OFF WITH ENGINE COLD AND CHECK WATER ..MAKE SURE RADIATOR NOT BLOCKED,,PLASTIC BAG ETC. THIS SOUNDS LIKE LOW WATER OR RADIATOR ..STOPPED UP INSIDE ..IF YOU HAVE GOOD HEAT IT'S FULL OF WATER. REPLACE T STAT B4 RADIATOR..IT'S CHEAPER. ALSO CHECK FOR RADIATOR COOLING FAN OPPERATION..I,M RULING OUT THE WATER PUMP.

Hi there you could try flushing the system, it sounds like your Heater Matrix ( heater core ) this could be blocked with limescale/antifreeze deposits etcor just broken.

hope this helps , please rate :)

possible air in your system you need to bleed air out of your system make sure heater valve is open and radiator cap open when car is cold take all air out and fill as needed

No heat is often a symptom of low coolant, usually followed by overheat. There are other controls that regulate heater, but right now, re-fill the cooling system with engine running and heater on high, then check for leaks (coolant you lost went somewhere...you need to determine where) Low coolant will damage your engine. Take care of that first, then if heater still does not work, then do diagnosis on that. (if you loose the engine heat won't matter, will it!)

You most likely have air in the cooling system.You would need to bleed the cooling system of air.There should have bleed screws near water neck,or thermostat.Do this cold.Remove the radiator cap and fill full.Then start the engine and loosen the screws and watch for nothing but coolant to flow out(no air or bubbles).When you are sure the air is gone out of the cooling system,shut the bleeder screw off,and fill radiator up and test to see that engine runs cool,and you have heat at all speeds and rpm s.The electric cooling fan should come on at a tempuratue of about 215 or so.But just as important,the cooling fan should cut off at a lower tempurature.If the cooling fan does not do this,you still have air in the system.If you can not get the air out this way,then do this.Remove the radiator cap and reservoir cap and fill them both up full.The reservoir needs to be over the fill mark a good deal.Replace the caps.Start the engine with ac and heat off.Let it run until the engine gets to about 212 or 215 degrees and shut the engine off.Wait about 30 minutes and check the reservoir to see if the coolant has dropped.It should have dropped.If the reservoir has dropped or not ,do this again and again untill the reservoir drops in coolant level,and engine temp is good(fan goes on and goes off).Remember to refill the reservoir as needed as it drops,not to run out of coolant.

make sure your coolant fluid level is good, than check the valve that controls the amount of coolant that flows to the heat exchanger inside your dashboard, make sure it is wide open. (find it by having someone inside the car move the heat control from hot to cold and back while you are under the hood looking for the valve. Sometimes the cable that goes from the dashboard heat/temp control to the coolant valve comes off.