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I don't get it I've flushed the coolant changed my thermostat and upgraded to a mishimoto fan and shroud. Car seemed to cool fine for a week or two. Then I changed the spark plugs and its over heating again. Also I noticed looking at my NC miata there is foam bellow radiator. But not in my rx8. I read something about foam keeping the car cool. Anyways wtf is my car getting so hot!!! I feel like the stock components should keep the car cool. I'm so worried about blowing my seals. Also I took off the engine cover in hopes of cooling. But it's not any better. Should I even be worried? These temps are being taken from right below the thermostat.
1. Mishimoto parts are generally over-priced junk. We recommend Koyo and CSF on this site for good reasons.
2. Have you verified the fans are turning on in the proper sequence and running at the proper speeds?
3. Have you verified all air is out of the system? The RX-8 is not the easiest car to burp for some reason.
4. Have you verified the thermostat is working? Is it oriented properly (jiggler up)? Is it a quality brand like Mazda, AC Delco, Stant, or Gates?
5. Do you have the undertray in place? It is critical for directing air into the radiator.
6. Did you foam at least 3 sides of the radiator with pipe insulation?
7. Does it overheat at idle? If so, that absolutely should not happen. The fans should keep temps reasonable.
8. What coolant are you using and in what proportion glycol to distilled water?
summary: make sure your system coolant pressure is good by checking your cap, coolant level, and coolant quality.
Pressure test your radiator coolant overflow tank cap and make sure at max operating temperature that your coolant is in between the min/max lines on the overflow tank. Issue 1: If it is not holding pressure (13 psi at max coolant temp conditions), then the boiling point of the FL-22 coolant is lower and (the boiling coolant in hot spots) significantly lowers the heat transfer surface area leading to overtemps. Issue 2: Too little coolant volume in the overflow tank will lead to lower system pressures at op temperature leading to lower coolant boiling points. Issue 3: Wrong coolant type/mixture and air bled from system (SD stated this above).
Occasional gurgling (of coolant flow as heard from the driver' seat) at idle is normal
Last edited by wannawankel; 10-22-2019 at 02:07 PM.
Listen to these guys above. Don’t drive it.
Those temps are very high...
Originally Posted by wannawankel
summary: make sure your system coolant pressure is good by checking your cap, coolant level, and coolant quality.
Pressure test your radiator coolant overflow tank cap and make sure at max operating temperature that your coolant is in between the min/max lines on the overflow tank. Issue 1: If it is not holding pressure (13 psi at max coolant temp conditions), then the boiling point of the FL-22 coolant is lower and (the boiling coolant in hot spots) significantly lowers the heat transfer surface area leading to overtemps. Issue 2: Too little coolant volume in the overflow tank will lead to lower system pressures at op temperature leading to lower coolant boiling points. Issue 3: Wrong coolant type/mixture and air bled from system (SD stated this above).
Occasional gurgling (of coolant flow as heard from the driver' seat) at idle is normal
Originally Posted by Steve Dallas
A few unvarnished thoughts:
1. Mishimoto parts are generally over-priced junk. We recommend Koyo and CSF on this site for good reasons.
2. Have you verified the fans are turning on in the proper sequence and running at the proper speeds?
3. Have you verified all air is out of the system? The RX-8 is not the easiest car to burp for some reason.
4. Have you verified the thermostat is working? Is it oriented properly (jiggler up)? Is it a quality brand like Mazda, AC Delco, Stant, or Gates?
5. Do you have the undertray in place? It is critical for directing air into the radiator.
6. Did you foam at least 3 sides of the radiator with pipe insulation?
7. Does it overheat at idle? If so, that absolutely should not happen. The fans should keep temps reasonable.
8. What coolant are you using and in what proportion glycol to distilled water?
Originally Posted by Loki
Do you have the plastic engine undertray in place?
243F is WELL into death territory. Don't let this happen.
Does it overheat standing still or at speed?
Originally Posted by UnknownJinX
There is supposed to be foam all around the radiator to make sure the air is forced through the radiator.
The difference the engine cover will make is pretty minimal.
Don't drive the car until you fix it.
Alright everyone I have a update. Thanks for the tips. I saw this a little late as I've already ordered a mishimoto thermostat to replace the autozone Thermostat I can't remember the brand. This will be the third thermostat I've gone through. I found something peculiar while swapping all my solenoids today... I noticed whoever worked on the car before me had used steel hose ties on the upper and lower coolant hoses. Seemed like it could have been restricting coolant flow. I guess the mechanic found it to difficult to move the oem hose ties up to the squeezing point. It was definitely difficult with minimal space to work with. Once I replaced the steel hose clamp with the oem clamps I gave the car a start and recorded my temps. I did notice my car seems to only overheat in idle when A/C is on. With the A/C off the car starts the fans at 214°F and cools down to 209°-210°F when the hood is closed it definitely becomes a oven temps seem to rise quicker and take longer to cool down. I also noticed temps typically higher on the top half of the Thermostat housing coolant return hose is typically 2-4° lower than the top hose. Seems to be the same story on the water pump. As a FYI the car does not over heat while in motion. I've driven this car for long trips over 2 hours and no issue till I come to a stop sign or red light for long periods. Once I start moving my temp goes down. Also my under tray is there but my car is definitely missing the foam around the radiator but I don't think that really effects idle temps, does it? My coolant was just flushed and changed. I'll follow up with the brand. I just know it's a 50/50 premix because I don't want to risk any corrosion. I can bleed the system again but I'm pretty sure after 600 miles any air in the system should be gone.
summary: make sure your system coolant pressure is good by checking your cap, coolant level, and coolant quality.
Pressure test your radiator coolant overflow tank cap and make sure at max operating temperature that your coolant is in between the min/max lines on the overflow tank. Issue 1: If it is not holding pressure (13 psi at max coolant temp conditions), then the boiling point of the FL-22 coolant is lower and (the boiling coolant in hot spots) significantly lowers the heat transfer surface area leading to overtemps. Issue 2: Too little coolant volume in the overflow tank will lead to lower system pressures at op temperature leading to lower coolant boiling points. Issue 3: Wrong coolant type/mixture and air bled from system (SD stated this above).
Occasional gurgling (of coolant flow as heard from the driver' seat) at idle is normal
Originally Posted by Steve Dallas
A few unvarnished thoughts:
1. Mishimoto parts are generally over-priced junk. We recommend Koyo and CSF on this site for good reasons.
2. Have you verified the fans are turning on in the proper sequence and running at the proper speeds?
3. Have you verified all air is out of the system? The RX-8 is not the easiest car to burp for some reason.
4. Have you verified the thermostat is working? Is it oriented properly (jiggler up)? Is it a quality brand like Mazda, AC Delco, Stant, or Gates?
5. Do you have the undertray in place? It is critical for directing air into the radiator.
6. Did you foam at least 3 sides of the radiator with pipe insulation?
7. Does it overheat at idle? If so, that absolutely should not happen. The fans should keep temps reasonable.
8. What coolant are you using and in what proportion glycol to distilled water?
Some generic coolants like that contain 2EHA which will eat your coolant seals over time. It's a rotary specific problem. Use Mazda FL22 only or make very sure this coolant doesn't contain 2EHA.
By the looks of it the stock clamp has compressed the hose? It looks deformed, you may want to replace it.
So the only thing unaccounted for is the proper function of both fans. Can you confirm they both turn on and both go to high speed above 210 or something like that?
I don't think a 3rd thermostat is necessary if the 2nd one didn't fix the problem.
Some generic coolants like that contain 2EHA which will eat your coolant seals over time. It's a rotary specific problem. Use Mazda FL22 only or make very sure this coolant doesn't contain 2EHA.
Not rotary specific. Honda for example also hates 2EHA and extended use will eat through the head gasket. One of the guys who documented the issue is a Buick owner as well.
It's just that head gaskets are much easier and cheaper to replace than coolant seals.
Some generic coolants like that contain 2EHA which will eat your coolant seals over time. It's a rotary specific problem. Use Mazda FL22 only or make very sure this coolant doesn't contain 2EHA.
By the looks of it the stock clamp has compressed the hose? It looks deformed, you may want to replace it.
So the only thing unaccounted for is the proper function of both fans. Can you confirm they both turn on and both go to high speed above 210 or something like that?
I don't think a 3rd thermostat is necessary if the 2nd one didn't fix the problem.
The fans are brand new. They cool temps down and I can continuously get the car to cool but the A/C has to be off. You can see the pattern in the photos above. The hottest temp recorded was with the A/Car on. As soon as I turned off the A/Car you see the temps go down. So I'm sure the fans are working but I'm not sure they are working at full potential. How do I check?? Also the new thermostat will open at lower temps. I want to see if that does the trick. After taking off the steel screw on hose clamps the hoses went back to normal. I'd imagine I should maybe change them before they break.
A new set of stock fans pull an impressive amount of CFM. Aftermarket fans usually under-perform the stock fans. The ones that are proven to be at least as good are 2 models of FAL shrouds. I don't know the specs on your Mishimoto fans, but I suspect they are not as good as a good set of OE replacement fans and probably under-perform the rated specs. So, being new does not necessarily mean anything.
The only trouble with the stock fans is that they slow down over time, and/or they have debris (such as airbox grommets) fall in them and burn them out.
The fans might be new but they run on relays. Maybe there's a problem there.
The fan logic is roughly this:
AC off:
- at 190F start fan 1 on low speed
- at 205 start both fans on high speed
AC on:
- start fan 2 whenever compressor is engaged
- at 190F also start fan 1 at low speed
- at 205 both fans on high full time
Someone can correct me, I'm going by memory.
The gist of it is that if the fans are only turning on when you hit 210ish, but not at 190, the car is heatsoaking, and AC is just making it worse.
See if your car behaves that way^^.
The lower temp thermostat shouldn't make any difference because by the time you get to 200, its full open anyway.
Do you see bubbles in the coolant overflow while the car is running? Start it cold with the cap off to see better, and it let it warm up.
A new set of stock fans pull an impressive amount of CFM. Aftermarket fans usually under-perform the stock fans. The ones that are proven to be at least as good are 2 models of FAL shrouds. I don't know the specs on your Mishimoto fans, but I suspect they are not as good as a good set of OE replacement fans and probably under-perform the rated specs. So, being new does not necessarily mean anything.
The only trouble with the stock fans is that they slow down over time, and/or they have debris (such as airbox grommets) fall in them and burn them out.
So the Mishimoto fan is rated at 1150 cfm on one twelve inch fan. Our 8s have two fans which means I should be getting 2300 cfm with these fans. There are also more blades on these than your stock units. I wasn't able to find the stock fans cfm rating. I'm going to foam the radiator in a few minutes because as you all know. The Thermostat didn't do anything. I don't think this will either but who knows, it could be air flow issues?
I'll be that guy... Mishimoto is shitty garbage... also oem fans are around 1235cfm....
The only fan that I would consider an upgrade from oem is FAL420 or 480.
Like those above said put in the foam around the rad, and if you can get the fans to turn on at a lower temp than oem( tune or controller mod) . Oh and make sure that they are sucking air into the engine bay and not trying to blow it out.
The foam will help but not at idle. Idle cooling needs the fans to work properly. Did you check the fan turn on thresholds as suggested?
Originally Posted by sonicsdaman
I'll be that guy... Mishimoto is shitty garbage... also oem fans are around 1235cfm....
The only fan that I would consider an upgrade from oem is FAL420 or 480.
Like those above said put in the foam around the rad, and if you can get the fans to turn on at a lower temp than oem( tune or controller mod) . Oh and make sure that they are sucking air into the engine bay and not trying to blow it out.
What do you mean by "the fan turn on thresholds?" My fans turn on and off just as the manual says. At the intervals listed in the manual. I put foam in and wow! What a difference in temperature while moving. Unfortunately wasnt my solution though. I'm beginning to think my radiator could just be corroded or something because far left of the radiator/transmission cooler are at decent temps. But the right side is constantly higher temps. The temps measured on the right end of the radiator/transmission cooler line up with temps I'm getting from my obd scan tool.
What do you mean by "the fan turn on thresholds?" My fans turn on and off just as the manual says. At the intervals listed in the manual. I put foam in and wow! What a difference in temperature while moving. Unfortunately wasnt my solution though. I'm beginning to think my radiator could just be corroded or something because far left of the radiator/transmission cooler are at decent temps. But the right side is constantly higher temps. The temps measured on the right end of the radiator/transmission cooler line up with temps I'm getting from my obd scan tool.
Nice work on the foam. I meant the on/off temps, so I guess that checks out.
Would you say the side where hot water comes in from the thermostat is the one that's higher, and the side where cooled coolant returns to the engine is the cooler one?
What kind of temperature difference are we talking? How hot is the return line compared to the radiator entry line?
Going further down the list of possible causes, ado you see bubbles in the coolant overflow tank while the engine is running? (do not open it when hot, start the cold car with the reservoir open and let it warm up)
Regarding Foam, it directs air at speed, it also keeps the hot engine compartment air from flowing back around the radiator when stopped and the fans are running. If hot air flows back around, you are stuck trying to cool the engine with 160 degree air.
Nice work on the foam. I meant the on/off temps, so I guess that checks out.
Would you say the side where hot water comes in from the thermostat is the one that's higher, and the side where cooled coolant returns to the engine is the cooler one?
What kind of temperature difference are we talking? How hot is the return line compared to the radiator entry line?
Going further down the list of possible causes, ado you see bubbles in the coolant overflow tank while the engine is running? (do not open it when hot, start the cold car with the reservoir open and let it warm up)
pictures are top hose/bottom hose on start
Then its top hose/bottom hose after warm up. Lower than mid on temp gauge.
"Doing its job" isn't the same as "doing its job well enough".
I would check the temperatures horizontally across the radiator. The radiator has a series of vertical channels that sink heat to air via horizontal fins. If some of the vertical channels are blocked or otherwise restricted, no coolant will travel those and you'll lose cooling capacity. It may work well enough until you stress the engine at which point heat output will overwhelm the radiator's ability to reject the heat to air.
10-21-2019, 05:28 PM
