All mazda 929 have this problem when the coolant level is dropped the heater core has no fluid in it since it ts off of the engine block . hence it cannot recive any coolant to heat the car. the best way to fix this is bleed the system of air . when filling coolant squezze the return hose with the cap on the rad it will force fluid bact to the core and push the air out once you do this a few times you will see the rad fluid droped fill it up and run the car . this should solve this problem
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Re: Heating / Cooling System Malfunction
Get a complete cooling system flush and fill, you may need to also replace the heater core, blower motor, blower motor resistor, there is also possibility the thermostat might not have been properly installed or maybe wrong part, its not good but parts can be in wrong boxes with wrong part numbers.
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if you are not getting any heat when it is at normal operating temperature , you may have air trapped in the cooling system . some vehicles have a bleeder screw in which you would remove the screw and add coolant without the engine running until there is no air bubbling out of the hole that you removed the screw from .then put the screw back in and let it run keeping an eye on your temp gauge . If you have no bleeder screw , then you have to either jack the front of the car up high or park on a VERY steep incline and let the car idle making sure the coolant stays full until the trapped air is purged from the cooling system . In most cases when air is gone out , you will get good heat from your heater and should run at normal temp. you can also call mazda first to see if it has a bleeder screw and exactly where it is located .
first make sure there is not any air in the cooling system by running with radiator cap off and keeping coolant level full, but it sounds as if you have a blown head gasket. sure signs are consistant over heating, loss of coolant with no evidence of leak, or smoke out of tail pipe with a bitter sweet smell to it.
Does the heater blow cold air from the vents or do you mean the there is no airflow from the vents? cold air from the dash vents when the heater control valve is set fully hot could be an air pocket in the cooling system. The radiator sits slightly lower than the engine causing air pockets to get trapped in the engine when you replace the coolant. you'll have to purge the cooling system to restore flow to the heater core. No airflow (blower motor inop) this could be a bad blower motor transistor. pin test the blower motor circuit.
Check the cooling fan, its sensor, the relay, the fuse. On most cars the fan is not needed on the highway, but engine overheats it it doesn't switch on inside the city. Also, clean the system with a special liquid according to the directions on the can and use coolant after that, water causes corrosion. While pouring/filling/cleaning, keep the heat switch on max heating to allw circulation via the heating radiator.
Most likely you have a bad thermostat
is stuck and not letting coolant to flow to your radiator.
check your coolant level if is normal
replace the thermostat
if you live air pockets on your cooling system then also cause to over head when adding new coolant open the bleeder valve if you cant find it just add coolant whit the engine running
when the new thermostat open will release the air pocket and you will see a sudden drop of you coolant level, then add more on till the radiator is full again.
never drive your car for long is your engine is over heating that will cause a blown head gasket and mayor repairs.
if your on the street and just notice than your car is over heating turn your A/C off set it on heating maximum fan max heat and of coarse roll down all your windows.
it be real hot for you but that will save your engine.
the heater core on your car is like a baby radiator and bypass the engine thermostat that will help to cooled down a lot .
hope this help you and good luck.
First of all, it doesn't sound like your thermostat is working correctly to keep good hot/warm air coming , so I would change that, or have it changed for better heating inside. If you lift the hood & look in front of your radiator, On the engine side, you'll see a fan attached to, or in front of the radiator. It won't come on until the coolant temperature gauge gets up to proper operating temperature. Without getting in to too much detail, have your thermostat changed, and my guess is everything else will start working as it should, and whoever does the work, should know enough to check the fan operation when they do the thermostat.
no im a mechanic it sounds like that you have an air lock in the cooling system .i am familiar with ford freda and bongo and the design where the engine is is a bit far from the radiator ,so the problem with air locks magnifies.really the solution is just drain the water and refill it slowly while you are pressing and releasing,just repeat the action on the top radiator hose to get rid of any air trapping within the system,it's as simple as that really.you want it to have just water and no air as this will cause a blockage.