Rx-8 overheating safety feature????
12-09-2019, 10:38 AM
#1
Rx-8 overheating safety feature????
Does the RX-8 have an overheating safety feature built in?
I say this because I bought the car with a bad thermostat. I replaced with a low temp thermostat and it just went bad 3 days later. I was on highway today and right when I saw the temp gaue move I pulled over and shut it down. Engine was extremely cool , but the coolant was not. Car would not turn on.... Waited 10 min and it turned right on. I started it and rushed to next exit, right when temp showed 220 on my odb adapter it acted like it cut fuel right away and the same thing happened. I bought this car with a lot of small issues that I managed to fix without much money. Engine seems great, turns on fast and everything. I don't see how a new thermostat goes out that fast..... But it did....
I say this because I bought the car with a bad thermostat. I replaced with a low temp thermostat and it just went bad 3 days later. I was on highway today and right when I saw the temp gaue move I pulled over and shut it down. Engine was extremely cool , but the coolant was not. Car would not turn on.... Waited 10 min and it turned right on. I started it and rushed to next exit, right when temp showed 220 on my odb adapter it acted like it cut fuel right away and the same thing happened. I bought this car with a lot of small issues that I managed to fix without much money. Engine seems great, turns on fast and everything. I don't see how a new thermostat goes out that fast..... But it did....
12-09-2019, 10:44 AM
#2
There is no such safety feature. Not being able to restart when hot is a sign of engine or fuel pump failure. Did you have compression tested before you bought the car? What lead you to believe the thermostat was bad?
I'm not sure what 'engine was cool but coolant was hot'. That's not possible, coolant doesn't make its own heat.
It's possible the car overheated not because of thermostat failure but for other issues in the cooling system. Is the plastic engine and rad undertray still attached?
I'm not sure what 'engine was cool but coolant was hot'. That's not possible, coolant doesn't make its own heat.
It's possible the car overheated not because of thermostat failure but for other issues in the cooling system. Is the plastic engine and rad undertray still attached?
12-09-2019, 11:06 AM
#3
There is no such safety feature. Not being able to restart when hot is a sign of engine or fuel pump failure. Did you have compression tested before you bought the car? What lead you to believe the thermostat was bad?
I'm not sure what 'engine was cool but coolant was hot'. That's not possible, coolant doesn't make its own heat.
It's possible the car overheated not because of thermostat failure but for other issues in the cooling system. Is the plastic engine and rad undertray still attached?
I'm not sure what 'engine was cool but coolant was hot'. That's not possible, coolant doesn't make its own heat.
It's possible the car overheated not because of thermostat failure but for other issues in the cooling system. Is the plastic engine and rad undertray still attached?
Its not a question of if it was the thermostat, it was the thermostat. Simply not letting water in, been watching the car very closely with my ODB bluetooth adapter and a temperature laser. I flashed the ECU with Mazda Edit and deleted all the emissions items and set fans for 175F cut on. Car runs at 169F - 183F at all times after ECU flash and new thermostat. Today it just stopped letting water out of the block........... bad thermostat.
12-09-2019, 12:03 PM
#4
Smoking turbo yay
To answer your question, there is no safety feature that I am aware of for engine overheating.
And you are sure the old t-stat was in one piece when you took it out? If it wasn't then it could be clogging up some lines. You can also test the current one with a bowl of hot water to see if it works.
And you are sure the old t-stat was in one piece when you took it out? If it wasn't then it could be clogging up some lines. You can also test the current one with a bowl of hot water to see if it works.
12-09-2019, 02:48 PM
#5
To answer your question, there is no safety feature that I am aware of for engine overheating.
And you are sure the old t-stat was in one piece when you took it out? If it wasn't then it could be clogging up some lines. You can also test the current one with a bowl of hot water to see if it works.
And you are sure the old t-stat was in one piece when you took it out? If it wasn't then it could be clogging up some lines. You can also test the current one with a bowl of hot water to see if it works.
Well i believe you guys if you know this to be 100% FACT
But to me it seemed like a 100% fuel cut when it hit 220F, nothing when i stepped on gas just a bog noise. I had a MK3 Turbo Supra before so i am pretty experienced to what a fuel cut feels like. I could be wrong though but it happened twice at 220F and i was carefully watching temps on my ODB adapter when it happened, I have been EXTREMELY safe with this car since i have gotten it. There was no power loss, smoking engine or extremely hot engine bay, just instant fuel cut it felt like. Engine was cool to the touch , very cool.....
Thats what made me think there was some safety feature that has to do with operating temps in the ecu. There is fuel maps for operating temps in the fuel maps from what i see in Mazda Edit.
This is making me thermostat paranoid now, makes me wanna run open for a bit to avoid this again.
Last edited by finalturismo; 12-09-2019 at 02:54 PM.
12-09-2019, 03:22 PM
#6
Smoking turbo yay
I can't imagine a safety feature that cuts the fuel completely since that can be very dangerous at certain situations. At most, you go into limp mode, which the RX-8 does for certain situations like when it detects a fault with the oil injectors, but not overheating. At 220F, your temp gauge needle probably wouldn't have even moved(which is why an OBD2 device is recommended).
Like Loki said your case is odd, since the heat is generated by the engine, so if your t stat is stuck open then your whole cooling system should be cool, while a stuck closed one would make the engine hot and the rest of the system cool. Hmmm...
Like Loki said your case is odd, since the heat is generated by the engine, so if your t stat is stuck open then your whole cooling system should be cool, while a stuck closed one would make the engine hot and the rest of the system cool. Hmmm...
12-09-2019, 03:29 PM
#7
I can't imagine a safety feature that cuts the fuel completely since that can be very dangerous at certain situations. At most, you go into limp mode, which the RX-8 does for certain situations like when it detects a fault with the oil injectors, but not overheating. At 220F, your temp gauge needle probably wouldn't have even moved(which is why an OBD2 device is recommended).
Like Loki said your case is odd, since the heat is generated by the engine, so if your t stat is stuck open then your whole cooling system should be cool, while a stuck closed one would make the engine hot and the rest of the system cool. Hmmm...
Like Loki said your case is odd, since the heat is generated by the engine, so if your t stat is stuck open then your whole cooling system should be cool, while a stuck closed one would make the engine hot and the rest of the system cool. Hmmm...
Ya strange.... i dunno
It was a Mishimoto T-stat, died on day 3 .............
https://www.ebay.com/itm/Mishimoto-L...72.m2749.l2649
12-09-2019, 05:09 PM
#8
Which part of the engine was cool, exactly?
Did you have a compression test at any point?
Use a stock thermostat, there is no benefit to the Mishimoto's lower temperature threshold.
We know this to be true because people have seen higher temps than 220. Not that it's a good idea, but it does happen.
It's possible your fuel pump is what's overheating. Known issue on older 8's
Did you have a compression test at any point?
Use a stock thermostat, there is no benefit to the Mishimoto's lower temperature threshold.
We know this to be true because people have seen higher temps than 220. Not that it's a good idea, but it does happen.
It's possible your fuel pump is what's overheating. Known issue on older 8's
Last edited by Loki; 12-09-2019 at 05:12 PM.
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12-10-2019, 03:58 AM
#9
RX-Heaven
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I also agree that there is no built in ecu logic to cut fuel or spark if the coolant were to get too hot. As stated above, overheating fuel pumps would cause a no start issue and it is common on the early cars.
Replace the thermostat with an original Mazda thermostat and bleed the cooling system properly. An improperly bled cooling system can leave trapped air pockets in the system resulting in an apparent overheating condition, you could also have a no heat situation or on and off hear as the air moves through the heater core. And finally you can see a fluctuating coolant temp gauge as the coolant and air flow past the sensor they cause the sensor to read differently.
Finally, perform a proper compression test with a rotary compression tester to ensure you have good compression. This is key as you do not want to be throwing parts at a tired engine.
Replace the thermostat with an original Mazda thermostat and bleed the cooling system properly. An improperly bled cooling system can leave trapped air pockets in the system resulting in an apparent overheating condition, you could also have a no heat situation or on and off hear as the air moves through the heater core. And finally you can see a fluctuating coolant temp gauge as the coolant and air flow past the sensor they cause the sensor to read differently.
Finally, perform a proper compression test with a rotary compression tester to ensure you have good compression. This is key as you do not want to be throwing parts at a tired engine.
12-10-2019, 07:14 AM
#10
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What everyone else said: if the car won't restart after running hot, you have other issues than overheating.
Vaguely related:
175°F fan temp is too cool and could increase the rate of carbon/ash build-up. Similarly, don't get another lower temp t-stat, for basically the same reasons.
Just use an OEM t-stat with an upgraded radiator. And I'd just set the fan trigger temps to be 10°F below the OEM settings.
Vaguely related:
175°F fan temp is too cool and could increase the rate of carbon/ash build-up. Similarly, don't get another lower temp t-stat, for basically the same reasons.
Just use an OEM t-stat with an upgraded radiator. And I'd just set the fan trigger temps to be 10°F below the OEM settings.
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