Car random overheat

[nigel89]

Guys I have a mazda axela 2005 manual car.When I stay at idle for more than 5 minutes temp gauge go up suddenly up to 4/3 of the gauge and fans start running loud..But when I rev the engine hard the gauge come back to normal within a second.(maximum 3 seconds).After that car acts normal for hours without any issues.car doesn't overheat when driving,not in traffic idle,But if i wait about more than 5 minutes in dead stop idle the gauge starts rising...I went to a mechanic and he replaced the thermostat but the issue is still there.To make this even complicated this doesn't happen every time,happen only like 2 times per week...

No coolant leaks
I tried bleeding air
Fan working fine..

Is this an electrical issue?

[SomeGuy]

My first guess would have been thermostat too but since it's already been replaced my next guess would be water pump. Could be seizing up and revving gives it that extra little kick it needs to turn.

[MazdaMike02]

The 2 times per week thing makes me believe it is a head gasket. I would go to Carquest, Napa or whatever and buy head gasket test strips. They're little strips of litmus paper you dip it in the coolant compare to the bottle.

If its not the head gasket its the heater core. I had one where the heater core was partly collapsed and kept making the car overheat. This car had new coolant, thermostat, water pump. I never thought it would be the heater core as I flushed it with water. I replaced it anyway and sure enough temps were normal again and it never went over 1/2 which was about 90-92 degrees celcius.

[g_tsb]

thermostat maybe? should regulate the engine temperature. i just replaced mine from an 05. temp should only be about 1/2 guage

[sarujo]

Seriously, did you even bother to read the first post!? He already said the thermostat was changed and still the problem persist.

thermostat maybe? should regulate the engine temperature. i just replaced mine from an 05. temp should only be about 1/2 guage

[Lux]

Check the integrity of the water temperature sender. It could be providing false output to the instrument cluster.
Harness integrity would be the next inspection.
If you're not confident with electrical diagnosis, I suggest you not attempt it. Not worth mistakenly shorting something out and potentially popping the ECU or cooking some wires.
I know the thermostat was replaced, but was it an OEM part? If aftermarket, what temperature range is it?
New parts could still be defective unless TESTED and PROVEN otherwise. It happens often.
If it checks out okay, the water pump is the next possibility, but testing that would be a tough one (need to measure output flow rate, somehow).
You could have obstructions in the cooling system, including a restricted radiator or hoses.

[evildiesel]

electrical maybe yes and know.. could be a faulty thermostat even brand new they can fault.. now while your driving it wont over heat.. so your rad is doing its job, in traffic you get some air through the rad. how thick and how long do you sit in traffic? your fans are kicking on.. so those are functioning fine and reading the the engine is heating up. Id double check its the right thermostat and even possibly look into putting another one in temporarily to see if the thermostat is functioning fine as it is mechanical not electrical.

that happen to me i got a faulty thermostat put a new one in and hasnt happened since. does your car have any firing issues? chugging? misfiring etc?

[TheMAN]

probably air pocket in cooling system... need to purge the air

[evildiesel]

probably air pocket in cooling system... need to purge the air

Apparently thats been done already.. usually mechanics will run the car afterwards to see if it overheats and waits to see if the airs out.. on "most occasions"
depends on the mechanic i guess