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My daughter bought a 2003 Mazda 6. She thought she was getting a deal but it's the exact opposite. Problem after problem after problem. It's overheating. I have replaced the thermostat, the leaking radiator, and hoses going to them. It seemed at first to do it, but after running a while temp started jumping up again. I don't know what to do next. Water pump going out or malfunctioning? I took it to AutoZone and they checked it out, tons of problems but nothing to do with water pump. Please tell me someone else has had this problem and can't help. ANY ADVICE is greatly appreciated.
 

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I have a 2003 Mazda .When A/C is blowing full blast car overheats but as soon as I turn the heat on the temp drops immediately...I changed the thermostat and the radiator...thought it was fixed and it started doing it again.
 

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Not sure to which thread should I reply, you did left out the part about it overheating only when the AC is on.
If that is truly the case as your daughter (I assume) stated, your issue most likely is the radiator fans.
Both fans should be blowing at full blast when the AC is on, is that the case?

Temp drops when you turn the heat on as the cabin blower helps cool down the refrigerant.
 

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Welcome to the forum (and your dad).

I replied to his thread. Please choose and make one threat the "official" one or you are going to get bits and pieces here and there.
 

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Ill just respond to this and let him know. But no my fiancee said he watched them and when i turned it on full blast one fan would kick on and then when it shut off the other would kick on but they arent blowing at the same time
 

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Welcome to the forum (and your dad).

I replied to his thread. Please choose and make one threat the "official" one or you are going to get bits and pieces here and there.

Ill just respond to this and let him know. But no my fiancee said he watched them and when i turned it on full blast one fan would kick on and then when it shut off the other would kick on but they arent blowing at the same time
 

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Welcome to the forum (and your dad).

I replied to his thread. Please choose and make one threat the "official" one or you are going to get bits and pieces here and there.
Wow! You immediately made the connection for the father and daughter.


I think the fans are designed to run together and not alternately. I wonder if the electrical connection is reversed somewhere...
 

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Wow! You immediately made the connection for the father and daughter.


I think the fans are designed to run together and not alternately. I wonder if the electrical connection is reversed somewhere...
I dont think its electrical cause when i got the car on valentines weekend of this year that monday i took it to the shop and they did a complete run through of the car and the only electrical issue was my neutral safety switch which they fixed. However o figured if they looked through my entire car then they should have seen if the fans were working properly but maybe they were at that time and they started to fail and i just never knew.
 

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Merged both threads together.

Welcome to the forum, both of you! :)

Sorry to hear about all the nonsense you've been dealing with, sounds like the previous owner didn't take care of it at all.

Are your fans staying on after the car is turned off, or running very fast (loud) sporadically? It's possible your FCM (Fan control module) is on the fritz and needs to be replaced, which is a fairly common issue in aging 6s. It's also common enough that people will sometimes replace the FCM with cheap fleaBay ones and those usually break pretty quickly.
 

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Merged both threads together.

Welcome to the forum, both of you! :)

Sorry to hear about all the nonsense you've been dealing with, sounds like the previous owner didn't take care of it at all.

Are your fans staying on after the car is turned off, or running very fast (loud) sporadically? It's possible your FCM (Fan control module) is on the fritz and needs to be replaced, which is a fairly common issue in aging 6s. It's also common enough that people will sometimes replace the FCM with cheap fleaBay ones and those usually break pretty quickly.
That i wouldnt know...i just know when i turn the ac on full blast one kicks on and when it turns off then the other kicks on....doesnt sound loud at all. How would ik if the fcm is going out?
 

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So let's be clear, when the AC is on both fans should be running at full speed.
Start by verifying what is installed in your vehicle, do you have OEM fans and module?
 

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So let's be clear, when the AC is on both fans should be running at full speed.
Start by verifying what is installed in your vehicle, do you have OEM fans and module?
Only one fan comes on at a time. When one shuts off the other comes on.
 

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Yeah, we got that.
Let's establish what is working and what is not.
-With a cold engine and the AC off, start the car. Open the hood and observe which fan cycles (or if both do).
-After you determined that, turn the AC on while observing the compressor's clutch. What happens? Does one of the fans turn on when the clutch engages? Is it the same one that was running when the AC was off? Do the fans alternate when the clutch engages, how?

As most electrical gremlins this one might be tricky to diagnose, add to that the fact that you do not know what has been done to the vehicle. Maybe shoot a video while you are preforming the above and share it.
Also share a pic of your fans and control module, does it look OEM or if someone has messed around with it?
It could also be as simple as a grounding issue, one fan "steals" ground from the other.
 

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Yeah, we got that.
Let's establish what is working and what is not.
-With a cold engine and the AC off, start the car. Open the hood and observe which fan cycles (or if both do).
-After you determined that, turn the AC on while observing the compressor's clutch. What happens? Does one of the fans turn on when the clutch engages? Is it the same one that was running when the AC was off? Do the fans alternate when the clutch engages, how?

As most electrical gremlins this one might be tricky to diagnose, add to that the fact that you do not know what has been done to the vehicle. Maybe shoot a video while you are preforming the above and share it.
Also share a pic of your fans and control module, does it look OEM or if someone has messed around with it?
It could also be as simple as a grounding issue, one fan "steals" ground from the other.
My fiancee got both fans to work properly at the same time. However it is still overheating? Maybe waterpump? And everything he chexked was fine...he even tested all the relays to the fans and they all work properly.
 

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You are not providing much information. How did he do that? What was wrong with it?
First you said it only happened when the AC was on, is that still the case?
Your water pump is not the issue since you said the car doesn't overheat when the heat is on which means the refrigerant is circulating.

It is either your fans not running at the required speed (we would know more if you shared some info) or there is an air lock in the line that was not purged properly when the rad was replaced.
 

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If I may suggest, let the guy who works directly on your car answer and discuss what is needed here so as to avoid confusion. Passing of information from one person to another with someone in-between that doesn't have the technical know-how will make it difficult to diagnose a problem remotely. A few simple details might be missed out but can be the key for the solution.

The forum members here are not there to observe the car physically. As suggested earlier, please take a picture and post it here or a video and post the link here.
 

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I am curious what the "bunch of other problems" was. A misfire will superheat the catalyst and could cause overheating Running too lean could also contribute.

Please list all trouble codes that you had when AutoZone told you the news.

Overheating quick list for me is:
bad thermostat
faulty fan controller
low coolant (or air in system)
not holding pressure (bad cap or cracked overflow)
faulty water pump
then more unlikely stuff.

Let us know and good luck.

@Robbie Dove @JadeCDove
 

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I am curious what the "bunch of other problems" was. A misfire will superheat the catalyst and could cause overheating Running too lean could also contribute.

Please list all trouble codes that you had when AutoZone told you the news.

Overheating quick list for me is:
bad thermostat
faulty fan controller
low coolant (or air in system)
not holding pressure (bad cap or cracked overflow)
faulty water pump
then more unlikely stuff.

Let us know and good luck.

@Robbie Dove @JadeCDove
  1. I called my friends mechanic who works mainly on imports and explained the situation and hes 95% sureee its a blown head gasket...fans are running properly now cause there was a loose ground and we fixed it...all relays work properly. And the only code my car threw was the o2 sensor and the purge valve sensor which have both been replaced. Radiator has no leak at all and is still holding coolant. And yes it still overheats with ac on and everything is working properly so only other thing that could be wrong is blown head gasket...so having him come pull the engine and take a look.
 

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  1. I called my friends mechanic who works mainly on imports and explained the situation and hes 95% sureee its a blown head gasket...fans are running properly now cause there was a loose ground and we fixed it...all relays work properly. And the only code my car threw was the o2 sensor and the purge valve sensor which have both been replaced. Radiator has no leak at all and is still holding coolant. And yes it still overheats with ac on and everything is working properly so only other thing that could be wrong is blown head gasket...so having him come pull the engine and take a look.
Couple things...

Your Mazda, while technically a Japanese car, is 80 - 85% Ford, including the engine - the import guy may or may not know any more than a regular mechanic.

The only way a blown head gasket is going to cause overheating is if it's bad enough that coolant is leaking into the engine - more commonly, the blown gasket is the result of overheating. In either scenario, you'd see a loss of coolant or bubbles appearing in your reservoir - which you are saying isn't happening.

If you do actually have a blown gasket, your engine would be running/sounding like garbage and you could test that without pulling the engine by doing a compression test.

Please try to save yourself a ton of work and test things properly before jumping to conclusions that may or may not be true - we're just doing our best with the info we've been given.
 

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  1. I called my friends mechanic who works mainly on imports and explained the situation and hes 95% sureee its a blown head gasket...fans are running properly now cause there was a loose ground and we fixed it...all relays work properly. And the only code my car threw was the o2 sensor and the purge valve sensor which have both been replaced. Radiator has no leak at all and is still holding coolant. And yes it still overheats with ac on and everything is working properly so only other thing that could be wrong is blown head gasket...so having him come pull the engine and take a look.
Straight to blown head gasket?

Is your oil frothy? check dipstick after running
Is there oil in your coolant?
Have you checked the spark plugs for deposits?
Have you done a compression check?
 
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