Mysterious high temperature issue... Overheating? Or bad sensor?
#1
Mysterious high temperature issue... Overheating? Or bad sensor?
2007, Series 1, 6 speed.
Hello all,
First time writing so be gentle,
I've been a member for a while and have found many useful bits of info, ideas and fixes for my RX8 during this time, so a big thanks to all who contribute to this site ( even if some info is incorrect) we can all learn from each other. OK, that's enough butter.... I've been having some trouble diagnosing a 'overhaeting' issue. Temp guage moved while I was driving spirited, (felt my stomach sink a little) immediately slowed down and temp guage returned to normal position. Did some checks at home the next day:
No leaks, anywhere.
Coolant level full. No spray.
Thermostat changed to Mishimoto. Opens fully a few degrees cooler than OEM.
Bled cooling system properly. (No air bubbles) Even removed coolant hose from throttle body while nose was elevated to make sure.
Started up, checked for leaks. None.
Checked hoses for stiffness: Squishy when cold, firm when hot, as it should be.
Both radiator fans are also working properly.
Topped up coolant.
Reved up for about 2-3 mins at 3K. Still no leaks.
Redline it a couple times. No change on temp guage. Both radiator fans on.
Shutdown engine, fans stay on for about 5-7 mins as they normally do.
I was feeling pretty good until I took a easy drive that evening and saw the temp guage move up again. Even driving chill.
Anyone have any insights into this? Maybe a similar problem?
I have extensively searched the forums, but haven't found anyone who has had a problem like this.
Thanks in advance, and I apologioze if this has been solved and I just couldn't find the thread.
Douglas S.
Hello all,
First time writing so be gentle,
I've been a member for a while and have found many useful bits of info, ideas and fixes for my RX8 during this time, so a big thanks to all who contribute to this site ( even if some info is incorrect) we can all learn from each other. OK, that's enough butter.... I've been having some trouble diagnosing a 'overhaeting' issue. Temp guage moved while I was driving spirited, (felt my stomach sink a little) immediately slowed down and temp guage returned to normal position. Did some checks at home the next day:
No leaks, anywhere.
Coolant level full. No spray.
Thermostat changed to Mishimoto. Opens fully a few degrees cooler than OEM.
Bled cooling system properly. (No air bubbles) Even removed coolant hose from throttle body while nose was elevated to make sure.
Started up, checked for leaks. None.
Checked hoses for stiffness: Squishy when cold, firm when hot, as it should be.
Both radiator fans are also working properly.
Topped up coolant.
Reved up for about 2-3 mins at 3K. Still no leaks.
Redline it a couple times. No change on temp guage. Both radiator fans on.
Shutdown engine, fans stay on for about 5-7 mins as they normally do.
I was feeling pretty good until I took a easy drive that evening and saw the temp guage move up again. Even driving chill.
Anyone have any insights into this? Maybe a similar problem?
I have extensively searched the forums, but haven't found anyone who has had a problem like this.
Thanks in advance, and I apologioze if this has been solved and I just couldn't find the thread.
Douglas S.
#2
40th anniversary Edition
How many miles on your radiator ? At 100k, anything original in the cooling system is really suspect and failure prone. It represents the biggest threat to your engine.
Last edited by gwilliams6; 05-26-2018 at 07:10 PM.
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Douglas Straughn (05-27-2018)
#3
Moder8
iTrader: (1)
Define driving chill..... ; )
If slow, under 20 MPH, you can still have issues with air flow. I also suggest getting an ultragauge, best way to track temp and cheap.
and gw is right,
Here are a few things to check.. https://www.rx8club.com/series-i-tro...o-i-do-258334/
And, are you sure BOTH fans are on? Just one can do more harm than good.
And, there are a few cooling things in the congrats thread that I suggest looking at.
If slow, under 20 MPH, you can still have issues with air flow. I also suggest getting an ultragauge, best way to track temp and cheap.
and gw is right,
Here are a few things to check.. https://www.rx8club.com/series-i-tro...o-i-do-258334/
And, are you sure BOTH fans are on? Just one can do more harm than good.
And, there are a few cooling things in the congrats thread that I suggest looking at.
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Douglas Straughn (05-27-2018)
#4
The car has 84K on the odometer and I changed the radiator to a KoyoRad about one year ago after my OEM radiator sprung a leak.
#5
Define driving chill..... ; )
If slow, under 20 MPH, you can still have issues with air flow. I also suggest getting an ultragauge, best way to track temp and cheap.
and gw is right,
Here are a few things to check.. https://www.rx8club.com/series-i-tro...o-i-do-258334/
And, are you sure BOTH fans are on? Just one can do more harm than good.
And, there are a few cooling things in the congrats thread that I suggest looking at.
If slow, under 20 MPH, you can still have issues with air flow. I also suggest getting an ultragauge, best way to track temp and cheap.
and gw is right,
Here are a few things to check.. https://www.rx8club.com/series-i-tro...o-i-do-258334/
And, are you sure BOTH fans are on? Just one can do more harm than good.
And, there are a few cooling things in the congrats thread that I suggest looking at.
Thanks for the link, I'll check it out.
#6
Smoking turbo yay
A wild guess:
There are some pads around the OEM radiator that make sure the air will be forced through the radiator, not around it.
When you replaced the OEM one, did you make sure the new Koyo has some kind of padding around it to make sure the air only flows through the radiator?
There are some pads around the OEM radiator that make sure the air will be forced through the radiator, not around it.
When you replaced the OEM one, did you make sure the new Koyo has some kind of padding around it to make sure the air only flows through the radiator?
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Douglas Straughn (05-27-2018)
#7
A wild guess:
There are some pads around the OEM radiator that make sure the air will be forced through the radiator, not around it.
When you replaced the OEM one, did you make sure the new Koyo has some kind of padding around it to make sure the air only flows through the radiator?
There are some pads around the OEM radiator that make sure the air will be forced through the radiator, not around it.
When you replaced the OEM one, did you make sure the new Koyo has some kind of padding around it to make sure the air only flows through the radiator?
I'm going to have my mechanic come by asap and plug into the comp. to see if it's trying to tell me something.
Douglas S.
#8
Registered
iTrader: (1)
Things to consider...
- jammed thermostat (even though you replaced it, there could be a foreign object obstructing it)
- compromised water seal such that exhaust gases enter the cooling circuit. Test coolant for exhaust gases (there's a simple chemical test, any parts store can help you)
- cooling circuit is unable to pressurize. Cracked overflow tank (a crack elsewhere would produce a leak you would notice) or failed rad cap
- actually bad sensor, but that's pretty rare. They're simple devices.
What coolant are you using?
- jammed thermostat (even though you replaced it, there could be a foreign object obstructing it)
- compromised water seal such that exhaust gases enter the cooling circuit. Test coolant for exhaust gases (there's a simple chemical test, any parts store can help you)
- cooling circuit is unable to pressurize. Cracked overflow tank (a crack elsewhere would produce a leak you would notice) or failed rad cap
- actually bad sensor, but that's pretty rare. They're simple devices.
What coolant are you using?
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Douglas Straughn (05-28-2018)
#9
Things to consider...
- jammed thermostat (even though you replaced it, there could be a foreign object obstructing it)
- compromised water seal such that exhaust gases enter the cooling circuit. Test coolant for exhaust gases (there's a simple chemical test, any parts store can help you)
- cooling circuit is unable to pressurize. Cracked overflow tank (a crack elsewhere would produce a leak you would notice) or failed rad cap
- actually bad sensor, but that's pretty rare. They're simple devices.
What coolant are you using?
- jammed thermostat (even though you replaced it, there could be a foreign object obstructing it)
- compromised water seal such that exhaust gases enter the cooling circuit. Test coolant for exhaust gases (there's a simple chemical test, any parts store can help you)
- cooling circuit is unable to pressurize. Cracked overflow tank (a crack elsewhere would produce a leak you would notice) or failed rad cap
- actually bad sensor, but that's pretty rare. They're simple devices.
What coolant are you using?
Jammed thermostat - Could be. I did a basic check while idling, on the stiffness of the hoses while cold and they were soft, then again when hot (fans on) and they were solid which would indicate the thermostat opening and allowing coolant flow. Right? I mean, I'm not a professional but that does make sense.
Compromised water seal - I will have to look into this.
Cooling circuit unable to pressurize - Rad cap did look a little worn so I replaced it 3 days ago. Cracked overflow tank, it's not impossible but I have no visible leaks anywhere nor am I losing coolant. It's at the same level its been at since the thermostat install.
Bad sensor - I was thinking about this recently, because this new thermostat does open a few degrees cooler that the OEM one maybe the ECU is a bit confused and isn't sure how to handle it?
I used a Prestone coolant and water mix. 50/50 (or thereabouts)
Thanks,
Douglas S.
#10
Registered
iTrader: (1)
I know Prestone guarantees compatibility with all makes/models, but the general wisdom around here is to use Mazda FL22 only. Something about 2-EHA, which FL22 doesn't have, being corrosive to rotary coolant seals.
I have the same thermostat as you and nothing freaks out. There is nothing the computer can do to react to a low temperature anyway.
The soft/hard hose thing is a decent indicationthe system has pressure, but not whether the thermostat is fully open.
Does your car still have the plastic undertray under the engine and rad? You need that, it's an active part of directing air to the rad. People have overheated without it.
One simple test of the sensor would be another thermometer. An infrared one if you have it, but anything that goes to 100C will do. The block should be close to the reported water temp if the car is idling stationary.
Is the rebuild a Mazda one? There were issues with their process long ago where extra sealant would be left behind and work loose in the water stream, and eventually end up jamming something important. There hasn't been a case reported here in ages,. ut you never know. Anyone can make a mistake.
BTW, the needle moves around 230F. You're going to eant to minimize the time you spend near there, these engines don't survive that temperature well.
I have the same thermostat as you and nothing freaks out. There is nothing the computer can do to react to a low temperature anyway.
The soft/hard hose thing is a decent indicationthe system has pressure, but not whether the thermostat is fully open.
Does your car still have the plastic undertray under the engine and rad? You need that, it's an active part of directing air to the rad. People have overheated without it.
One simple test of the sensor would be another thermometer. An infrared one if you have it, but anything that goes to 100C will do. The block should be close to the reported water temp if the car is idling stationary.
Is the rebuild a Mazda one? There were issues with their process long ago where extra sealant would be left behind and work loose in the water stream, and eventually end up jamming something important. There hasn't been a case reported here in ages,. ut you never know. Anyone can make a mistake.
BTW, the needle moves around 230F. You're going to eant to minimize the time you spend near there, these engines don't survive that temperature well.
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Douglas Straughn (05-28-2018)
#11
I know Prestone guarantees compatibility with all makes/models, but the general wisdom around here is to use Mazda FL22 only. Something about 2-EHA, which FL22 doesn't have, being corrosive to rotary coolant seals.
I have the same thermostat as you and nothing freaks out. There is nothing the computer can do to react to a low temperature anyway.
The soft/hard hose thing is a decent indicationthe system has pressure, but not whether the thermostat is fully open.
Does your car still have the plastic undertray under the engine and rad? You need that, it's an active part of directing air to the rad. People have overheated without it.
One simple test of the sensor would be another thermometer. An infrared one if you have it, but anything that goes to 100C will do. The block should be close to the reported water temp if the car is idling stationary.
Is the rebuild a Mazda one? There were issues with their process long ago where extra sealant would be left behind and work loose in the water stream, and eventually end up jamming something important. There hasn't been a case reported here in ages,. ut you never know. Anyone can make a mistake.
BTW, the needle moves around 230F. You're going to eant to minimize the time you spend near there, these engines don't survive that temperature well.
I have the same thermostat as you and nothing freaks out. There is nothing the computer can do to react to a low temperature anyway.
The soft/hard hose thing is a decent indicationthe system has pressure, but not whether the thermostat is fully open.
Does your car still have the plastic undertray under the engine and rad? You need that, it's an active part of directing air to the rad. People have overheated without it.
One simple test of the sensor would be another thermometer. An infrared one if you have it, but anything that goes to 100C will do. The block should be close to the reported water temp if the car is idling stationary.
Is the rebuild a Mazda one? There were issues with their process long ago where extra sealant would be left behind and work loose in the water stream, and eventually end up jamming something important. There hasn't been a case reported here in ages,. ut you never know. Anyone can make a mistake.
BTW, the needle moves around 230F. You're going to eant to minimize the time you spend near there, these engines don't survive that temperature well.
Loki,
Thank you for your reply. I will look for that coolant at my dealership. I live in Barbados and it's sometimes difficult to find speciality products like that.
I have not removed the plastic undertray.
The car is still on it's original engine.
I'll look into the thermometer reading idea, thats a good way to rule out certain theories.
I'm compiling all of these great ideas and hopefully have my mechanic come by soon so we can go through them and get to the bottom of this. I miss my braps
Thanks again,
Douglas S.
#12
Moder8
iTrader: (1)
The foam may be a biggie. What you are missing is air flow through the radiator. I do NOT recommend expanding foam. What I use is pipe foam, for a 1" or 1.5" pipe. It is fairly rigid and can be wedged or taped in place to fill the large gaps. What happens if this is not done is the air just flows around the radiator. The fans cut off at 20 something mph, the shroud is in the way, the battery tray is in the way and heat shield for the air box is in the way. By far the easiest way for air to get by is around the radiator.
You can put the foam in from the bottom, with the undertray out.
You can put the foam in from the bottom, with the undertray out.
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Douglas Straughn (06-01-2018)
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Douglas Straughn (06-01-2018)
#14
///// Upscale Zoom-Zoom
Have the coolant cap checked for pressure leaks. A loss in pressure in the coolant system will result in a dramatic lowering of the boiling point of the coolant. Unfortunately our system runs at high pressure to elevate the boiling point and any losses in pressure result in a boiling point depression.
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Douglas Straughn (06-01-2018)
#15
The foam may be a biggie. What you are missing is air flow through the radiator. I do NOT recommend expanding foam. What I use is pipe foam, for a 1" or 1.5" pipe. It is fairly rigid and can be wedged or taped in place to fill the large gaps. What happens if this is not done is the air just flows around the radiator. The fans cut off at 20 something mph, the shroud is in the way, the battery tray is in the way and heat shield for the air box is in the way. By far the easiest way for air to get by is around the radiator.
You can put the foam in from the bottom, with the undertray out.
You can put the foam in from the bottom, with the undertray out.
Many thanks.
Douglas S.
#16
Have the coolant cap checked for pressure leaks. A loss in pressure in the coolant system will result in a dramatic lowering of the boiling point of the coolant. Unfortunately our system runs at high pressure to elevate the boiling point and any losses in pressure result in a boiling point depression.
Thanks again,
Douglas S.
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Douglas Straughn (06-04-2018)
#18
So after many, many tests. My mechanic and I have come to the conclusion that the water jacket seal must be compromised as there is no other explanation that supports the 'type' of overheating issue I am having. I have exhausted all other theories. I've learned a lot through this experience tho so at least I got something out of it. Good news is, I had planned on having my engine rebuilt & street ported in July anyway so I already have all the new parts including Atkins Rotary new water jacket seal which they claim to be able to handle upto 150 deg. over the stock seal, so thats a plus. Now, if after the rebuild, its still overheating then we can have more discussions lol.
Just wanted to say thanks to everyone who had any form of input in this thread as all information was useful in some way. Great community. Great cars.
KR.
Douglas S.
Just wanted to say thanks to everyone who had any form of input in this thread as all information was useful in some way. Great community. Great cars.
KR.
Douglas S.
#19
Registered
iTrader: (1)
So after many, many tests. My mechanic and I have come to the conclusion that the water jacket seal must be compromised as there is no other explanation that supports the 'type' of overheating issue I am having. I have exhausted all other theories. I've learned a lot through this experience tho so at least I got something out of it. Good news is, I had planned on having my engine rebuilt & street ported in July anyway so I already have all the new parts including Atkins Rotary new water jacket seal which they claim to be able to handle upto 150 deg. over the stock seal, so thats a plus. Now, if after the rebuild, its still overheating then we can have more discussions lol.
Just wanted to say thanks to everyone who had any form of input in this thread as all information was useful in some way. Great community. Great cars.
KR.
Douglas S.
Just wanted to say thanks to everyone who had any form of input in this thread as all information was useful in some way. Great community. Great cars.
KR.
Douglas S.
Here's the thing: if the problem is in the engine, you rebuild it, everyone is happy. If the problem is outside of the engine, you rebuild the engine only to come back here with the same problem. So before you pull the engine, try to conclusively prove the source of the problem.
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Douglas Straughn (06-07-2018)
#20
Moder8
iTrader: (1)
My thought...
If the pressure check does not show a problem, it is not seal related.. Read Loki Post above again. It would suck if an external problem hosed your new build.
Did you try the foam around the radiator? Also, is the undertray tight against the frame rail? If you are not losing water I have a hard time thinking you have a water leak. But, airflow could be a problem.
And, Ultra-gauge. It will let you know exactly what is happening, what situation makes the temp go up, and what makes it go down.
And, check the CAT. Just pull the bolts at the front and look inside.
If the pressure check does not show a problem, it is not seal related.. Read Loki Post above again. It would suck if an external problem hosed your new build.
Did you try the foam around the radiator? Also, is the undertray tight against the frame rail? If you are not losing water I have a hard time thinking you have a water leak. But, airflow could be a problem.
And, Ultra-gauge. It will let you know exactly what is happening, what situation makes the temp go up, and what makes it go down.
And, check the CAT. Just pull the bolts at the front and look inside.
The following users liked this post:
Douglas Straughn (06-07-2018)
#21
My thought...
If the pressure check does not show a problem, it is not seal related.. Read Loki Post above again. It would suck if an external problem hosed your new build.
Did you try the foam around the radiator? Also, is the undertray tight against the frame rail? If you are not losing water I have a hard time thinking you have a water leak. But, airflow could be a problem.
And, Ultra-gauge. It will let you know exactly what is happening, what situation makes the temp go up, and what makes it go down.
And, check the CAT. Just pull the bolts at the front and look inside.
If the pressure check does not show a problem, it is not seal related.. Read Loki Post above again. It would suck if an external problem hosed your new build.
Did you try the foam around the radiator? Also, is the undertray tight against the frame rail? If you are not losing water I have a hard time thinking you have a water leak. But, airflow could be a problem.
And, Ultra-gauge. It will let you know exactly what is happening, what situation makes the temp go up, and what makes it go down.
And, check the CAT. Just pull the bolts at the front and look inside.
I cannot find the chemical test here in my country unfortunately (most shops have never even heard of it) and there is too much red tape to ship here.
Yes I have placed pipe foam around the radiator to channel more air into it.
I definatley do not have and external coolant leak.
Gutting the CAT was one of the first mods I made to the car, about 3 years ago.
Having the engine under any load causes the heat to go up exponentially. She will idle and rev all day long without much change in temp, but as soon as you start shifting above 4/5K temps rocket up. Or driving casually up an incline. I've actually based my routes around the steep hills so that I don't have any issues lol.
Thanks for the interest. Keep the ideas coming.
Douglas S.
#22
Moder8
iTrader: (1)
Ah, missed it the first few times..
Thermostat could still be an issue. Pressure goes both ways. If it is not working, entire system will be pressurized so hard and soft hoses does not help.
Also, if you put the heat on high, does the temp drop? This adds more cooling to the system. If it does, then you are likely short cooling capacity. Again, that points to thermostat. I would suggest pulling the thermostat and tossing it a pan on the stove to test. See when it opens (meat thermometer will do the trick). You could also try a test with the thermostat out. This is not a long term option, but would give you data. If it stays cool, thermostat. But, it can still run hot with thermostat out if flow is too high (water does not spend much of any time in the radiator).
Thermostat could still be an issue. Pressure goes both ways. If it is not working, entire system will be pressurized so hard and soft hoses does not help.
Also, if you put the heat on high, does the temp drop? This adds more cooling to the system. If it does, then you are likely short cooling capacity. Again, that points to thermostat. I would suggest pulling the thermostat and tossing it a pan on the stove to test. See when it opens (meat thermometer will do the trick). You could also try a test with the thermostat out. This is not a long term option, but would give you data. If it stays cool, thermostat. But, it can still run hot with thermostat out if flow is too high (water does not spend much of any time in the radiator).
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Douglas Straughn (06-13-2018)
#23
Water Foul
...and the coolant level has reduced without any visible signs of leaking.
If your coolant level is continuously doing down, and you do not have external leaks, and you do not have white smoke in your exhaust, you are either boiling it or you still have air in the system that is slowly bleeding out. My money is on the latter. When I replaced my radiator a few years ago, I carried a jug of distilled water in the car for about a week and topped off the level every time I shut the car off. Even though I followed the burping procedure in my garage, I did not get all the air out of the system in one shot.
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Douglas Straughn (06-13-2018)
#24
I did do the thermostat check (not with a thermometer) just to make sure the mechanism was working. I even checked the old one I replaced and that one is working as well.
Douglas S.
#25
If your coolant level is continuously doing down, and you do not have external leaks, and you do not have white smoke in your exhaust, you are either boiling it or you still have air in the system that is slowly bleeding out. My money is on the latter. When I replaced my radiator a few years ago, I carried a jug of distilled water in the car for about a week and topped off the level every time I shut the car off. Even though I followed the burping procedure in my garage, I did not get all the air out of the system in one shot.
I drove the car all day yesterday and my temperature didnt go above 220F because I was mostly in traffic and driving slowly. Short shifting under 3K. I did one hard pull on the homestraight to my house and temp went from 212F to 232F very quickly. I could smell that sweet coolant smell but still no leaks and no white smoke. Coolant level was slightly lower this morning.
Thanks
Douglas S.