Heater not working suddenly, warms up, not leaking now...

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poetnprophet

Member
:
Mazda5
Hello fellow Mazdas,

I have a 2009 Mazda 5, the heater just stopped working suddenly the other night. I smelled coolant and it started to overheat, so I pulled over and noticed some water near the rad on the drivers side.

It was late night so the next morning I checked it out, couldn't find any leaks. Filled the reservoir, ran it for about an hour and nothing leaked....i thought for sure a busted hose or even the heater core.

I then disconnected the hoses from the core at the firewall, and flushed the core in and out, nothing seemed clogged, all flowed fine. I then took apart the glove box and half the dash to look at the solenoids in the plenum. All are working, mainly the hot/cold. i can see it moving up and down when setting the temp. I can even hear the airflow change as the valve/solenoid moves.

I just cannot get any heat at all. Blower works well, all the vents work as they should. It seems like the hoses to/from the heater core are not flowing (they were nearly empty when I removed them), but I don't know where to go from here on this car. It's not overheating and it's not leaking coolant. I don't know where that water came from before, it was on the drivers side by the radiator, opposite the reservoir. But I can't get it to leak anymore.

Any ideas, anyone?

thanks,
Dave
 
You may have some air in the system. Keep topping it off with the engine running, parked on incline, and burbing the top radiator hose. Invest in a pressure tester kit. They're cheap and well worth. Test the whole system per cap specs and then test the cap it's self.


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OK,, but air in the line usually shows symptoms of overheating, which its not doing...now. Weird I know. Plus, it all happened suddenly so if there is air now it wasn't the cause of it all.
 
bsedgal said:
You may have some air in the system. Keep topping it off with the engine running, parked on incline, and burbing the top radiator hose. Invest in a pressure tester kit. They're cheap and well worth. Test the whole system per cap specs and then test the cap it's self.


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Click to expand...

^^Like he said. I had that issue when I replaced my thermostat. Try squeezing the upper radiator hose several times till you don't see any bubbles surfacing. Run the engine for a bit, check your guage, and turn the heater on full.
 
poetnprophet said:
OK,, but air in the line usually shows symptoms of overheating, which its not doing...now. Weird I know. Plus, it all happened suddenly so if there is air now it wasn't the cause of it all.
Click to expand...

It won't always over heat if there is some air in the system, but you may see the temp needle moving around a bit. Or it could be that the air is just plain trapped in the heater core, while the engine and ECT sensor are happy. The fact that you said it was leaking and now mysteriously is not immediately told me the system started sucking in air after the leak, either through the leak hole or from an empty reservior.

I wouldn't be as worried about the heat as I would the leak. You probably have a tiny crack in the radiator that you could spot in minutes with a pressure tester. Once a small leak starts and the engine loses coolant, there is no more coolant pressure, so its not unusual to see the leak seemingly stop.
 
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First of all, your engine has overheated. This overheat was not caused by your heater, but rather your heater stopped working because you no longer have proper coolant flow to the heater core inside of the car.

It is possible that the seam on the radiator failed while under pressure, the leaked coolant you saw had to come from SOMEWHERE!

Other possibilities are radiator cap, thermostat, engine head gasket...

At the current time it sounds like you have air trapped in the system that must be bled out. Also, make sure that you fill the radiator and not just the reservoir.

The best choice for you would be to pressure test the coolant system with the appropriate pressure tester to find where the coolant is leaking from. Then upon fixing the leak, you can bleed the air out of the heater core and the cooling system and proceed from there.

The radiators are made from several pieces, and the plastic end tanks are crimped on with a gasket o-ring... this is a common fail point on modern cars.
cooling-radiator.gif
 
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You can have a clog in a system, could be in a heater core or a radiator.
Could also be a failed thermostat.
Pressure test the system if you can, flush it and replace the thermostat as this will be a cheap start. If nothing, replace a radiator as they can be had for $100 or less.
Heater core you try to flush first as replacing that is a PITA.
 
OK ok guys, you were right. Pressure test found a leaking hose.

Now, I have been to 3 auto stores and none seems to carry this hose. It comes from the water pump and goes to like the oil filter? Can't find the correct molded hose. Anyone have a part number?
 
poetnprophet said:
I found it, but only on eBay. It's actually the oil cooler hose:
https://www.ebay.com (commissions earned)

Guess I'll have to wait until it arrives to see if it all worked.
Anyway, I appreciate all the help!
Click to expand...

Glad you were able to find the leak and the replacement hose.

Hoping that there is no damage from the overheat... You would probably be well served to think about doing the oil and oil filter change at the same time.
 
Hey everyone. I really appreciate all the feedback. You were all right, the new part arrive and once everything was buttoned up, no leaks at 12 psi and the heater now works really really well. Did a minor tune up as well, happy to be on the road again.

Cheers!
Dave
 
Glad you're all fixed up and always nice to see someone report back how things ended!


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