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Discussion Starter · #81 ·
I have ScanGauge2 but I always drive alone. If I'll have the chance, I'll let my wife to take a record of it. The thing is, I don't know exactly when I'll have that chance. Another thing, I am somehow forgetful of these things but I replied here hoping what I type will help me remember it so I can make a good estimate.
Always nice to have multiple inputs.


I went out and logged with my Accessport and forgot that I didn’t have coolant temp in my logging parameters, so I can’t give second-by-second coolant temps. I’m sorry.

However I can say that it reached 180°F/82°C in about 5 min with gentle driving. If you need more detail I can do it again tomorrow and log the coolant temps.

Here’s the upper radiator hose.

View attachment 243217
Thanks man. Your temp/time isn't that much different from mine, although it reaches that temp a little quicker for me.
I was worried that it was too fast with mine.

The hose also looks similar to mine, but to verify: Do you see a "dip" around that curved part of the hose?
Meaning that the outlet on the engine is slightly higher than the lowest part of the rad hose?

The more and more I think about it, and drive the car, the more I think the whole issue is coolant-level related.
 

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Your temp/time isn't that much different from mine, although it reaches that temp a little quicker for me.

Meaning that the outlet on the engine is slightly higher than the lowest part of the rad hose?
Yes these engines warm up quickly. If I hadn’t been driving so slow (less than 20mph) it would have heated up faster.

Yes it looks like the hose dips before it reaches the engine.
 

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Discussion Starter · #83 ·
So, it's been a while since my last update. I thought it would be a nice thing to let you know the outcome of all this.

In short: Incorrect purging of the air from the coolant system looks to be the culprit. If you ever find yourself in the same situation: Make sure the coolant is filled properly!

Long story:

At some point the temperatures here in Holland were high enough for me to just turn off the heater and turn on the A/C. I knew there wasn't a huge risk driving the short distance I had to go, so I just went for it.
To my surprise, temps remained at a steady 88-91degC during the whole trip (where previously it would spike to the max of 117degC the sensor could output).
The next day, I drove a short distance with no heater and no aircon. Same result, no issues whatsoever.

I decided to test my theory that the coolant level was negatively impacted by turning on the heat (resulting in added volume in the coolant loop).
I drove around for about 3 months without any issues.

Last week, as autumn is around the door and temps are dropping, I decided to address the issue, so I ordered some coolant.
Yesterday, I wanted to force the temp to spike, so I drove for a good while to heat up the system before stopped my car and turned on the heater.
The temps raised, as expected. But. Only to around 100degC (boiling point of water). And no matter how hard I tried, the temp remained that. When the fans turned on there was a small dip, but it never exceeded 103degC.
Not only that, but as soon as I started driving again, temps dropped back to 88degC with the heater and blower to max, and the A/C on.

Apparently, during the 3 months I was driving around with no heater, the air pocket has seemingly purged itself.
I will monitor the temps with heating on of course, but it seems that my problem has just gone away.
 

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I hope that it's just air and nothing else. I understand that you spent a lot of time troubleshooting it but as @DrFeelGood said, he sometimes "lose" his lung just to purge it.

Let us know later if things are normal after a long drive. Just a reminder, make sure you have the number of a towing company when you go for a long drive.
 

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Apparently, during the 3 months I was driving around with no heater, the air pocket has seemingly purged itself.
Did you add any coolant during those 3 months or did you notice the level go down at all? Hopefully the issue is resolved!

I don't know what it is about these cars but I have a heck of a time purging the cooling system. Following the Mazda shop manual to the letter on this does not get the job done. :sigh:
That’s funny because I’ve had no issues purging the system.
 

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Discussion Starter · #87 ·
Did you add any coolant during those 3 months or did you notice the level go down at all? Hopefully the issue is resolved!

That’s funny because I’ve had no issues purging the system.
I was doing some ghetto refills (basically blowing in the vent tube to get the excess fluid in the overflow tank to go back into the radiator (see earlier posts)), and I did once add 1L of coolant, but it was expelled almost as fast. But this was before I found out that turning off the heat seemingly solved the issue.

The overflow tank has not "refilled" itself since. It sits halfway min and max. And no, I did not add coolant after that. In fact, I wanted to address the issue last weekend and found I did not had an issue. I will check if I can add some coolant later this week, but the overheating thing seems to be gone.
 

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The overflow tank has not "refilled" itself since. It sits halfway min and max. And no, I did not add coolant after that. In fact, I wanted to address the issue last weekend and found I did not had an issue. I will check if I can add some coolant later this week, but the overheating thing seems to be gone.
I was just thinking that if the air was purged there should have been a drop in coolant level. Although it’s possible there wasn’t a lot of air, maybe a small pocket in a bad place?
 

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same issue and same damn trouble trying to figure out wtf.

I too noticed that changing the controls for the ac/heater drastically changes the temp on the gauge. ive been thinking pockt of air or head gasket. only thing that keeps me leaning towards head gasket is the coolant loss everytime i drive it. i see nothing on ground nor or oil or the exhaust. Mine only got Hot once when on a longer drive without adding coolant. it will normally ride right below 240 at most and ill change the settings on the heater and it will stay between 210-240 (half way to hot on gauge) varying as i drive.
this gives me some hope and give the car more consideration.

I guess ill restart by doing the proper procedure for the coolant refill. I have been opening up the Radiator to refill after the car has cooled down. When i do that I hear a suction sound when the cap is removed. This time i will add only thru the overflow tank. I too had been pushing the coolant over flow line to the radiator to the wrong side of the tank resulting in it not being able to suck the coolant out or , i assume, purge out any of the air from a pocket.

Thanks to the OP for the detailed information and people who responded with the great advice.

I tried to make my own thread but ive been at it for a month now and was overwhelmed with too many variables.

thanks Mazda 6 club.
 

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Please share your method of purging.
Sorry, didn’t notice your post!

I’ve used Mazda’s service manual method in the past but I’ve become a bit more lazy. The last time I refilled my coolant (after I completely rebuilt the engine, so there was no coolant at all in it) this is what I did:

  • Added coolant to radiator and overflow until full.
  • Ran the engine with the radiator cap off and squeezed hoses to encourage bubbles out and added coolant as necessary. I think I did that for two heat cycles.
  • I let it cool down and refilled as necessary.
  • I took it out for a spin knowing there was likely still air. I closely monitored the temp and pulled over when it started going up too high. I used a towel to open the radiator cap and added coolant directly.
  • I let it cool down for 30 min.
  • When I drove it after that the needle never went above the normal spot. I may have needed to add coolant to the overflow over the next day or two.

Hope that helps.
 

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same issue and same damn trouble trying to figure out wtf.

I too noticed that changing the controls for the ac/heater drastically changes the temp on the gauge. ive been thinking pockt of air or head gasket. only thing that keeps me leaning towards head gasket is the coolant loss everytime i drive it. i see nothing on ground nor or oil or the exhaust. Mine only got Hot once when on a longer drive without adding coolant. it will normally ride right below 240 at most and ill change the settings on the heater and it will stay between 210-240 (half way to hot on gauge) varying as i drive.
this gives me some hope and give the car more consideration.

I guess ill restart by doing the proper procedure for the coolant refill. I have been opening up the Radiator to refill after the car has cooled down. When i do that I hear a suction sound when the cap is removed. This time i will add only thru the overflow tank. I too had been pushing the coolant over flow line to the radiator to the wrong side of the tank resulting in it not being able to suck the coolant out or , i assume, purge out any of the air from a pocket.

Thanks to the OP for the detailed information and people who responded with the great advice.

I tried to make my own thread but ive been at it for a month now and was overwhelmed with too many variables.

thanks Mazda 6 club.
It’s possible your issue is from the overflow tube being dislodged. If that doesn’t fix it I’d recommend you do a coolant system pressure test. You can ‘rent’ them free (from auto parts shops) and they’re easy enough to use.

When I bought my MS6 the seller said it was loosing coolant. There weren’t puddles or smoke from exhaust. It turns out it was the little coolant hose going from the turbo to the egr valve leaking only when hot and at full system pressure. I only discovered it using the pressure tester.

Regarding your temp, 240° is pretty hot. Mine gets up to 210° or higher if I’m idling in traffic, but most of the time it’s around 195-205° depending on driving conditions.
 

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im not sure if it makes much of a difference but i dont have a turbo, i just have a 2005 6. not even sure if they're the same motor.

But the hose that goes to the overflow has actually been blown out of the over flow 2 times. im assuming it might have been whenever i had the hose pinched and it was the weakest link once the car built up enough pressure..

earlier i was reading a service manual and it showed to use a big funnel that is attached to the radiator and the pressure from the fluid pushes the air out of the sytstem instead of having to do the 5 minute 2500 rpm ive read in other service manuals. Tomorrow im going to give it a try and see if i get any different results.

also when adding the coolant when the car is still hot and radiator pressurized, doesnt oepning the cap force air into the system?? I tried doing that method originally and came to the conclusion it was the reason i kept getting air in to the system, or maybe not.


last question.. if i had a blown head gasket, would the car be able to still cool it self off once it started to get hot? or is it something that once it gets hot, its going to overheat and not cool back down until the engine is turned off and allowed to cool? Somehow mine manages to stay right under the boiling point.
 

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im not sure if it makes much of a difference but i dont have a turbo, i just have a 2005 6. not even sure if they're the same motor.

But the hose that goes to the overflow has actually been blown out of the over flow 2 times. im assuming it might have been whenever i had the hose pinched and it was the weakest link once the car built up enough pressure..

earlier i was reading a service manual and it showed to use a big funnel that is attached to the radiator and the pressure from the fluid pushes the air out of the sytstem instead of having to do the 5 minute 2500 rpm ive read in other service manuals. Tomorrow im going to give it a try and see if i get any different results.

also when adding the coolant when the car is still hot and radiator pressurized, doesnt oepning the cap force air into the system?? I tried doing that method originally and came to the conclusion it was the reason i kept getting air in to the system, or maybe not.


last question.. if i had a blown head gasket, would the car be able to still cool it self off once it started to get hot? or is it something that once it gets hot, its going to overheat and not cool back down until the engine is turned off and allowed to cool? Somehow mine manages to stay right under the boiling point.
Just so you know, this is the Speed6 section. But this is just generic cooling system issues.

When the radiator cap is off and the engine is heating up it won’t be sucking anything in the system since the coolant is expanding from heat. It’s pushing air/liquid out. The system pushes expanding coolant into the overflow (with the cap on), and when it cools down it sucks coolant back in. Just put the cap back on when the engine is off and it won’t suck in any air.

The effect of a damaged head gasket can be varied depending on where the damage is and how severe.

You really should do a coolant system pressure test before guessing about head gasket failure. If you’re losing coolant it’s going somewhere, and if you’re not burning it or it’s not going into your oil then it’s likely leaking from somewhere. Just because you don’t see the leak doesn’t mean it’s not.
 

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Discussion Starter · #97 ·
im not sure if it makes much of a difference but i dont have a turbo, i just have a 2005 6. not even sure if they're the same motor.

But the hose that goes to the overflow has actually been blown out of the over flow 2 times. im assuming it might have been whenever i had the hose pinched and it was the weakest link once the car built up enough pressure..
I had that happen to me as well, I have no idea why. I did adjust the hose and it never happened since. It seemed a bit long to me, tbh.


also when adding the coolant when the car is still hot and radiator pressurized, doesnt oepning the cap force air into the system?? I tried doing that method originally and came to the conclusion it was the reason i kept getting air in to the system, or maybe not.
It actually tries to push out the coolant, only when the coolant cools down again it will suck in air if you leave the cap off (don't) or when the overflow tank is empty (don't let it get empty).


last question.. if i had a blown head gasket, would the car be able to still cool it self off once it started to get hot? or is it something that once it gets hot, its going to overheat and not cool back down until the engine is turned off and allowed to cool? Somehow mine manages to stay right under the boiling point.
If you do have headgasket failure, it should be reasonably easy to identify:
  • "Mayonaise" under oil filler cap (you know when you see it)
  • White smoke from exhaust, more than normal "condensation"
  • Sometimes oily film (rainbow colours) in coolant overflow, but this is not a very reliable way to verify.

I too thought I had a failed headgasket, but I quickly discarded that when I figured out my temps stayed good when not using the heater.


Hello guys, back with a (small) update.

Now that it's getting colder, I've been slightly increasing the HVAC temp to see where the tipping point would be.
Well, it was 19,5 degrees C, when I had "The Issue" again.
Fortunately I had been carrying a 5L can of coolant in the trunk, so I immediately stopped as soon as I could, and checked the system.
Sure enough, the hose was under pressure, and when I removed the rad cap, only a little coolant came out and a lot of air (didn't smell funny btw).
I then poured in somewhere between 500mL and 1L (16fl oz - 32 fl oz, or 0,5qt to 1qt for you Imperialists :p. BTW, I was not expecting it to be that much) of coolant in before it started to overflow again. For good measure I also added some to the overflow tank, but that was more for my own peace of mind.

She behaved much better after, although I have had the issue happen a few more times (but no coolant leaking, I checked by putting some cardboard under the car when it was stationary).
Problem is, the issue is not predictable. After this last fill there was a traffic jam in the city I live in, and I spent a good hour in slow traffic, and during that time the temps never exceeded 93 degC. Even the fans didn't kick in.

So I will keep my can of coolant in the trunk, and immediately fill if she acts up again. I'm still convinced that this is the main issue, the bad refill.

Unfortunately, due to new COVID restrictions I have to work from home again, so trips with the car are far and few between.
On top of that, she gave me a P2119 code yesterday (not the first time, last time I only had to jiggle the connectors of the TPS). But I will check that out later.
 

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She behaved much better after, although I have had the issue happen a few more times (but no coolant leaking, I checked by putting some cardboard under the car when it was stationary).

On top of that, she gave me a P2119 code yesterday (not the first time, last time I only had to jiggle the connectors of the TPS). But I will check that out later.
When you put the cardboard under the car was the engine running? It is possible for the coolant to leak only when the system is under full pressure, and if that’s the case you wouldn’t see it unless the engine was operating as normal.

On my MS6, I had a coolant leak on the small hose from the turbo to the EGR, and I never saw it until I did a pressure test. On my former Hyundai, I also had a coolant leak I never saw.

I happen to have a spare throttle body if you feel like you need it. It could just be the connector causing your CEL or possibly the ground wire just in front of the HPFP (I’ve had several issues from that and ended up doing a good cleaning and sanding of the ground wire and plate to get it working reliably).
 
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