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Robert, UK Qualified Car Technician
Category: Car
Satisfied Customers: 4708
Experience:  Fully qualified / self employed garage technician in the UK
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My Mazda 5 is overheating but the heating blower only blows

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my Mazda 5 is overheating but the heating blower only blows cold air. I had the thermostat replaced but I the problem has come back
What engine does the car have?
How quickly does the car start to overheat?
Any coolant loss?
Is both or one of the pipes to heater matrix hot or cold?
Customer: replied 2 years ago.
This is a1.8T. The overheating starts as soon as the car gets up to temperature so around 5 minutes. I dont know about the pipes but the coolant fluid does start bubbling in the reservoir when hot
Ok..firstly check that the expansion tank cap isnt defective and is sealing properly but its certainly symptoms of coolant circulation issues..hence the cold air because no hot coolant is flowing through the matrix and can either be combination of the thermostat "which you've had replaced and hopefully the system was bled properly! you need to be sure its been done and no air is trapped in the system as that ca cause a coolant to bubble over" Another is a blockage somewhere in the coolant circuit/radiator or the water pump has doesnt sound headgasket related unless you have cross contamination with oil and coolant or actual coolant loss as a result or being forced out the tank itself..Normally a combustion leak test is done on the coolant system to see if any exhaust gases are leaking into the coolant system thus confirming a headgasket problem....but as above they need to see if coolant is actually circulating and the water pump is performing or not if it isnt then you'll just have no circulation whats so ever and then the engine will just effectively overheat rather quickly "which could effect the headgasket so bear that in mind" the water pump if i recall on these is timing belt driven so if that at fault? then you looking an entire Timing belt renewal kit job aswell as the water pump......
If the water pumps working as far as they can tell then id be looking at blockage in the system or Main radiator so they could try and back flush those is possible.....I do hope this helps....If you require to ask anything further then please do before you rate
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