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Hi !

A blue sky, 53 °F ... I drove open roof of my red GT...I looooooooove this car :smile::driving:

53°F, I push the heating to the maximum and ventilation too ... and the coolant temperature reaches around > 212°F. Without use, the temperature seems normal at around <194 °F

For info, new thermostat, water pump not replaced, 65000 miles
I see this for the 1st time for a convertible, I did it with other one.

Neophyte, I ask :grin:

I browsed the forum, several information exists but not on this subject ... or bad research.

Logic will say to me ... HIGH TEMPERATURE requested, the vehicle product accordingly...:grin:
 

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It is not an uncommon observation, but it is not intended as far as any documentation shows. In any case, 212 is not a cause for concern, so just enjoy it.
 

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Hi !

A blue sky, 53 °F ... I drove open roof of my red GT...I looooooooove this car :smile::driving:

53°F, I push the heating to the maximum and ventilation too ... and the coolant temperature reaches around > 212°F. Without use, the temperature seems normal at around <194 °F

For info, new thermostat, water pump not replaced, 65000 miles
I see this for the 1st time for a convertible, I did it with other one.

Neophyte, I ask :grin:

I browsed the forum, several information exists but not on this subject ... or bad research.

Logic will say to me ... HIGH TEMPERATURE requested, the vehicle product accordingly...:grin:
The light on the dash for high temperature comes on a 255 degrees, just FYI.

The operating temperature range you are seeing is normal and not problem at all, when you turn on the heat the coolant temp that is shown on the gauge will increase, that is a normal thing also.
 

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The operating temperature range you are seeing is normal and not problem at all, when you turn on the heat the coolant temp that is shown on the gauge will increase, that is a normal thing also.
Yeah, I get the same effect, many (all?) other owners do too. I would really like to know why, though. Turning on the heat only affects the position of the air blender flap in the cabin airflow. The coolant flow is not changed since coolant flows through the heat exchanger all the time (continuously). So the only effect is that heat is taken OUT of the coolant via the cabin fan blowing air over the heat exchanger. How does this INCREASE the coolant temps?

My only theory would be that the heater position is 'read' by the ECM, and the ECM does magic with the fuel maps (etc) to increase engine temps to account for that heat being pulled out of the coolant into the cabin, and maybe it overcompensates? Just a theory - only worth the paper it's written on.
 

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Yeah, I get the same effect, many (all?) other owners do too. I would really like to know why, though. Turning on the heat only affects the position of the air blender flap in the cabin airflow. The coolant flow is not changed since coolant flows through the heat exchanger all the time (continuously). So the only effect is that heat is taken OUT of the coolant via the cabin fan blowing air over the heat exchanger. How does this INCREASE the coolant temps?

My only theory would be that the heater position is 'read' by the ECM, and the ECM does magic with the fuel maps (etc) to increase engine temps to account for that heat being pulled out of the coolant into the cabin, and maybe it overcompensates? Just a theory - only worth the paper it's written on.
Would love to know why the engine temp displayed on the gauges shows an increase in temp when you turn on the heat also, but I know there are no changes to the engine fueling and timing when that happens. It is a weird thing though.
 

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The ECM doesn't read the heater control position, and the coolant flow is not changed with the heat setting, so the only thing left is the relative positions of the temperature transmitter and the thermostat. If the cooled coolant causes the thermostat to close slightly, the coolant temperature will go up. Unless the temperature transmitter is right at the thermostat, it will read that higher temperature.

What are the relative locations of the thermostat, heater core discharge, and transmitter?
 

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The ECM doesn't read the heater control position, and the coolant flow is not changed with the heat setting, so the only thing left is the relative positions of the temperature transmitter and the thermostat. If the cooled coolant causes the thermostat to close slightly, the coolant temperature will go up. Unless the temperature transmitter is right at the thermostat, it will read that higher temperature.

What are the relative locations of the thermostat, heater core discharge, and transmitter?
They are all on top of each other. I've attached some pictures of our thermostat housing below. This picture shows what the housing and coolant tube looks like on a Redline/GXP LNF engine. The "U" bent coolant pipe goes into the water pump on the disconnected end on this picture. On the other end, is the thermostat housing. Now the thermostat sits at the bottom end of this image but the cover is missing here. The cold water from the radiator comes in from this cap so everything in this part of the housing is hot water that has been passed through the engine. There are two tubes coming out of this housing and the one closest to the bottom of this picture is the hose that feeds the heater core. The return line comes in on the other side of the thermostat through the thermostat cap. So the feed and return from the heater core are right here in this area. Also, you can see the coolant temperature sensor still installed in this thermostat housing...it's between the two long silver tubes which are pointing towards the left side of the picture.



Here are how the heater hoses connect to this.



Now on the turbo cars, the coolant feed line for the turbo plugs in here too. So in the next image, you will see two holes, one on the right and one towards the middle right next to the heater line on the left. The Turbo coolant feed hooks up to the hole on the right and the coolant temperature sensor goes in the one on the left. You'll also notice an inset picture here. The little rectangle opening you see in that picture is where coolant can pass into or out of the engine block.



And here you can see the housing again with the thermostat in place with the cover on it. The one tube we saw in the first picture (that was the upper one of the two lines) is gone but with the cap in place you can now see the return tube for the heater core.



So here is my theory:

The heater core acts as an additional radiator. Once the thermostat has opened, hot coolant flows from the hot side of the thermostat up to the heater core. As you run your heater, this water is cooled off below the current operating temperature of the engine coolant. Now this "cold" water is introduced right above the thermostat and moves across the thermostat with the rest of the cool water coming from the radiator. However, this water is now cooler than the 180 operating temp thus the thermostat starts to close. Now the flow of coolant isn't where it needs to be to continue to maintain that optimum temp and engine coolant temps start to rise. So long as you use the heater, the average temp should remain higher than normal as there is the "extra cooled" water coming from the heater core directly to the thermostat.

Just my theory though.
 

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.........
So here is my theory:

The heater core acts as an additional radiator. Once the thermostat has opened, hot coolant flows from the hot side of the thermostat up to the heater core. As you run your heater, this water is cooled off below the current operating temperature of the engine coolant. Now this "cold" water is introduced right above the thermostat and moves across the thermostat with the rest of the cool water coming from the radiator. However, this water is now cooler than the 180 operating temp thus the thermostat starts to close. Now the flow of coolant isn't where it needs to be to continue to maintain that optimum temp and engine coolant temps start to rise. So long as you use the heater, the average temp should remain higher than normal as there is the "extra cooled" water coming from the heater core directly to the thermostat.

Just my theory though.
Except for you using 20 times as many words, isn't that what I said?
 

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Except for you using 20 times as many words, isn't that what I said?
Well, yes...except I was explaining it in the scope of knowing where all those things you asked about were located in relationship to each other so there was that. That took a few more words.
 

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Discussion Starter #11 (Edited by Moderator)
So here is my theory:

The heater core acts as an additional radiator. Once the thermostat has opened, hot coolant flows from the hot side of the thermostat up to the heater core. As you run your heater, this water is cooled off below the current operating temperature of the engine coolant. Now this "cold" water is introduced right above the thermostat and moves across the thermostat with the rest of the cool water coming from the radiator. However, this water is now cooler than the 180 operating temp thus the thermostat starts to close. Now the flow of coolant isn't where it needs to be to continue to maintain that optimum temp and engine coolant temps start to rise. So long as you use the heater, the average temp should remain higher than normal as there is the "extra cooled" water coming from the heater core directly to the thermostat.

Just my theory though.
UPDATE :frown: : The liquid in the Coolant surge tank , rubber hoses, charge air bypass, air in cabin airflow are cold...

I do not know the name of the technical part which looks like the charge air pass...cold too

Like I said in a other post, I had suspicious sound was on side of the water pump, sound like "hissing".

Sad update, I was so happy to drive again with a beautiful sun in winter.
 

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You mean when you turn the heater on you're getting cold air? Sounds like you may have air trapped in the system which is preventing the thermostat from operating properly. The hissing could be related to the air and higher coolant temps too. You may want to try re-bleeding the system especially if you just changed the thermostat.
 

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I have noticed that my car also runs hotter when the heat is used. In the past, in the winter I would often drive it on cold days, 0°C or less, with the roof down, windows up, and heater on full. The coolant temperature would rise but there were never any ill effects. I would never see it above 90°C/195°F without the heater, but with it, not uncommon to see it at 100° or more.

I can confirm, though...the cars do look good parked next to alpine lakes.

 

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Discussion Starter #14 (Edited)
You mean when you turn the heater on you're getting cold air? Sounds like you may have air trapped in the system which is preventing the thermostat from operating properly. The hissing could be related to the air and higher coolant temps too. You may want to try re-bleeding the system especially if you just changed the thermostat.
Yes, only cold air.

Sorry, I was not clear, thermostat was changed in April 2019, if the seller said right.

After 15 minutes, I had to move the car by and driving 4/5 minutes and curiously, the ventilation was blowing hot air and temp growing UP quickly. Park at my place ... and I apply the rule "ask if you don't know"

Same happen...heater getting warm air, temp going up... and cold air after
 

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I have noticed that my car also runs hotter when the heat is used. In the past, in the winter I would often drive it on cold days, 0°C or less, with the roof down, windows up, and heater on full. The coolant temperature would rise but there were never any ill effects. I would never see it above 90°C/195°F without the heater, but with it, not uncommon to see it at 100° or more.

I can confirm, though...the cars do look good parked next to alpine lakes.
Nice picture.

Isn't it true that the cars look good next to just about anything? And almost everything looks better next to an alpine lake?
 

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Yes, only cold air.

Sorry, I was not clear, thermostat was changed in April 2019, if the seller said right.

After 15 minutes, I had to move the car by and driving 4/5 minutes and curiously, the ventilation was blowing hot air and temp growing UP quickly. Park at my place ... and I apply the rule "ask if you don't know"

Same happen...heater getting warm air, temp going up... and cold air after
That sounds a lot like an air bubble trapped in the system. Temp raising quickly when air blowing hot sounds like a thermostat not opening and that can happen when you have an air bubble trapped down by the thermostat. Bleed the system again and see if you get more air out of it.
 

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Discussion Starter #17 (Edited)
That sounds a lot like an air bubble trapped in the system. Temp raising quickly when air blowing hot sounds like a thermostat not opening and that can happen when you have an air bubble trapped down by the thermostat. Bleed the system again and see if you get more air out of it.
This can just happen like this ? Without any intervention on the cooling system before, I mean between May and now? The bubble doesn't enter just like this? :|

I will try to do, I will scheck first on the forum how to do , in accordance with the rule cited above.
 

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This can just happen like this ? Without any intervention on the cooling system before, I mean between May and now? The bubble doesn't enter just like this? :|

I will try to do, I will check first on the forum how to do , in accordance with the rule cited above.
The bubble probably didn't just enter. It was probably somewhere that didn't cause a problem, and just moved to a new location that does.
 

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The bubble probably didn't just enter. It was probably somewhere that didn't cause a problem, and just moved to a new location that does.
^^^ This. And it seems our heater core is a favorite hang out of air bubbles and for whatever reason, they won't show up until you use the heater. So the fact he replaced it in May...and that you wouldn't normally use the heater in Spring, Summer, and maybe Fall...if you just started using your heater recently this would explain why it is only showing up now.
 

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^^^ This. And it seems our heater core is a favorite hang out of air bubbles and for whatever reason, they won't show up until you use the heater. So the fact he replaced it in May...and that you wouldn't normally use the heater in Spring, Summer, and maybe Fall...if you just started using your heater recently this would explain why it is only showing up now.

I use it a few time already. So it can happen too it look like after using already.

L:driving:ike mstrjon32, the temperature can be low in Switzerland with sunshine: we drive open roof and enjoy the sunshine.


I will try tomorrow.
 
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