I have an 02 aztek an the heat gage gets into the

You might have air lock in heater matrix when bleeding it put heat on full an nd let it get to temperature and bleed it then ..I had a Volvo f12 globetrotter that would overheat coming up Mont blanc at minus 20 outside temperature it was radiater changed perfect after

I don't think it's the radiator cap. I'd just replace the thermostat and see if that resolves the problem. you can also remove the thermostat just to see if it still runs hot.

if it runs hot with a new thermostat or without one, then have the engine professionally flushed. this is a pressurized flush.

without more information on mileage or vehicle, thats the best place to start on this issue.

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Did you bleed your system of air???....usually a bleed screw near the thermostat housing...get allllll the air out...simetimes the heater core is at the highest oart if the system..therefore if there is air in system..thats where the air settles and no coolant will flow through the heater cire!!

Bleeding air out of the system will purge also air out of heater core. Sometimes you may need to add a "flushing tee" (available from an autoparts store) to get some trapped air out of system.

If the air is not removed, if an air pocket is in the heater, you get no heat because coolant cannot move through at an adequate rate to be useful. In other areas it can cause hot spots in the engie that lead to cracked heads, blown head gaskets, or an engine that does not run well.

Air in the system , bad water pump , cooling fans not working ! Maybe you should take to a shop ?

YOU HAVE TO BLEED THE LINES THE ARE TWO NIPPLES ONE BY THE THERMOSTAT AND ONE BY THE WATER PUMP. YOU HAVE AIR IN THE LINES THE AIR BUBBLES BUILD UP IN FRONT OF THE THERMOSTAT AND PREVENT IT FROM ORENING ANY TIME YOU OPEN THE RADIATOR CAP OR ANYTHIN YOU MUST BLRRD THEM LINES YOU MIGHT HAVE TO DO IT A COUPLE TIMES BUT A RELATIVELY EASY FIX

HAve you check for a bad water pump?.. sometimes even new thermostat are defective too.
Do you know if your car has a relieve valve to bleed the cooling system. If the system has air it will over heat at low RPM's. Sometimes even flushing the radiator wont firx a cooling system with air.
So make sure about these two things I mentioned.
Please dont forget to rate me.

Change the thermostat and put in new coolant and MAKE SURE TO BLEED THE SYSTEM of air.

preform a pressurized collant flush , take it to a raidior shop to have it done , they will clean and blow out all blockages that might cause your car to over heat. also check to make sure you dont have air pockets in your anit freeze, if you do you need to bleed the system out after you have it flushed , your car should have a blead valve to let out the axcess air ,if not drive it down the road with the cooaint overflow cap off , not the radiator but you need to flush out the system first , add new anti freeze then bleed out all air pockets, hope this helps

remove coolant.remove thermostat remove bottom radiator hose to water pump.put a empty container under the radiator.take a water hose put it where thermostat goes flush out the rust in block.watch the water as it come out the water pump .if stream water is small keep flushing until you get a study sream of clear water. also flush out radiator. lower water pressure dont flush radiator it with high water pressure you could burst it. make clean the over flow jug .make sure it not stopped up.put in a new thermostat and radiator pressure cap. fill radiator with half antifreeze and half water.bleed the coolant system.