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Since it is getting hot at idle, I still strongly suspect the fans are not pulling enough CFM. It could be other things, but under-performing fans is the simplest explanation. Especially since Mishimoto. FAL or SPAL is what you want.
"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.
Well luckily. I have some photos of a time I checked the temps from radiator and oil coolers. Pics are left to right.
The first and last photos are the oil coolers. Technically radiators but not what we are talking about.
You need to measure across the big center radiator but keep in mind that the A/C condenser is in front of the radiator and it will interfere with your measurements.
Mishimoto's CFM rating is likely overstated, like so many of their other specs. They may not tell you that rating is peak for 1ms, while driving clockwise in a category 5 hurricane. Fortunately, they will tell you the shroud keeps the fan blades in place to prevent internal engine damage, though :
Mishimoto Mazda RX-8 aluminum fan shroud kits will considerably improve engine cooling functions and the overall performance of your vehicle. All Mishimoto fan shrouds are significantly lighter than standard fan shrouds and are a direct OEM fit. A Mishimoto fan shroud will effectively drive heat out of the engine bay and deliver a significant amount of cool air to your RX-8 radiator. The fan shroud also serves another very important purpose: securing the fan blades. The fan shroud will keep the fan blades in place, which otherwise could potentially damage other essential components in your engine. All Mishimoto aluminum fan shrouds include an adhesive protective strip. This adhesive-backed foam strip seals any remaining gap between the fan shroud and radiator so that the fans are only moving air that has passed through the radiator core as opposed to pulling in air from the engine bay, resulting in improved cooling efficiency.
Anyway, install a proper fan shroud, consider installing a fan temp relay kit to lower turn-on temps, replace those pinched hoses, and make sure the system is properly burped. That sequence is guaranteed to fix your problem. I guess you could do steps 2, 3 and 4 and see how things go, before taking the plunge on another shroud. (I wonder if you can leverage that "lifetime warranty" to receive a refund?)
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Last edited by Steve Dallas; 11-06-2019 at 08:38 AM.
Mishimoto's CFM rating is likely overstated, like so many of their other specs. They may not tell you that rating is peak for 1ms, while driving clockwise in a category 5 hurricane. Fortunately, they will tell you the shroud keeps the fan blades in place to prevent internal engine damage, though :
Anyway, install a proper fan shroud, consider installing a fan temp relay kit to lower turn-on temps, replace those pinched hoses, and make sure the system is properly burped. That sequence is guaranteed to fix your problem. I guess you could do steps 2, 3 and 4 and see how things go, before taking the plunge on another shroud. (I wonder if you can leverage that "lifetime warranty" to receive a refund?)
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Originally Posted by NotAPreppie
The first and last photos are the oil coolers. Technically radiators but not what we are talking about.
You need to measure across the big center radiator but keep in mind that the A/C condenser is in front of the radiator and it will interfere with your measurements.
Originally Posted by Loki
Have you or the previous owner ever put Water Wetter or similar products in the coolant?
Was the coolant clear when you drained it?
Pinched hoses are fixed. The car is properly burped did it the other day again. I can show you the over heating issue happened with the oem fans originally. Which is why I changed fans to begin with. Im going to invest in a relay because the fans cool just not when the A/C is on.
Yes first and last photos are the oil coolers. But the other two are measured directly from the main radiator from left to right. I was aiming above the transmission cooler.
No water wetter. I read on so many forums and people are saying it's snake oil. Previous owner haven't used it either according to shop notes on all the paper work.
Pinched hoses are fixed. The car is properly burped did it the other day again. I can show you the over heating issue happened with the oem fans originally. Which is why I changed fans to begin with. Im going to invest in a relay because the fans cool just not when the A/C is on.
Yes first and last photos are the oil coolers. But the other two are measured directly from the main radiator from left to right. I was aiming above the transmission cooler.
No water wetter. I read on so many forums and people are saying it's snake oil. Previous owner haven't used it either according to shop notes on all the paper work.
The transmission cooler is inside the lower tank of the radiator.
The heat exchanger in front of the radiator is the A/C condenser.
You need to take a lot of data points because each one of those channels can be individually blocked. That said, if you have a temperature spread of 40°F, between two points on the radiator, you probably need a new radiator.
Pinched hoses are fixed. The car is properly burped did it the other day again. I can show you the over heating issue happened with the oem fans originally. Which is why I changed fans to begin with. Im going to invest in a relay because the fans cool just not when the A/C is on.
Yes first and last photos are the oil coolers. But the other two are measured directly from the main radiator from left to right. I was aiming above the transmission cooler.
No water wetter. I read on so many forums and people are saying it's snake oil. Previous owner haven't used it either according to shop notes on all the paper work.
Yeah that's what I'm thinking. Maybe it's a partial block or corrosion. Thanks for the feedback
Pinched hoses are fixed. The car is properly burped did it the other day again. I can show you the over heating issue happened with the oem fans originally. Which is why I changed fans to begin with. Im going to invest in a relay because the fans cool just not when the A/C is on.
Yes first and last photos are the oil coolers. But the other two are measured directly from the main radiator from left to right. I was aiming above the transmission cooler.
No water wetter. I read on so many forums and people are saying it's snake oil. Previous owner haven't used it either according to shop notes on all the paper work.
I get what you are saying, but let me explain my thinking, and where it diverges from yours. The OE fans do slow down over time, and/or have debris get lodged in them. Replacing older fans can be a good idea, if they are no longer performing. However, choosing Mishimoto fans is not necessarily a good idea. Ratings aside, they probably perform worse than old stock fans. To those of us who have been around performance cars for a long time, Mishimoto is a ROFL joke. You could have saved money and ended up with better fans simply by visiting Rock Auto's web site. That said, if a relay kit does not solve it for you, invest in a FAL fan shroud. It will.
I get what you are saying, but let me explain my thinking, and where it diverges from yours. The OE fans do slow down over time, and/or have debris get lodged in them. Replacing older fans can be a good idea, if they are no longer performing. However, choosing Mishimoto fans is not necessarily a good idea. Ratings aside, they probably perform worse than old stock fans. To those of us who have been around performance cars for a long time, Mishimoto is a ROFL joke. You could have saved money and ended up with better fans simply by visiting Rock Auto's web site. That said, if a relay kit does not solve it for you, invest in a FAL fan shroud. It will.
Im going to have to switch back to stock fans then when I get the radiator. Also I had to drive my car somewhere recently and now the car seems to be over heating when I accelerate for any period of time. It overheated to the point that radiator fluid started blowing out of the reservoir cap.
Is your system at base condition - holding pressure (IIRC 13 psi setpoint) and coolant at the right concentration (and the metal surfaces inside your engine in top shape)?
Boiling point of coolant is dependent on system pressure - at lower pressure the coolant boils at a lower temperature (their colligative properties). Boiling coolant is a poorer heat transfer medium at the interface of the coolant and your engine.
You might have cooked your engine with these repeat overheats. Do you see bubbles in the overflow tank while the car is running but cold? Don't open it while the coolant is still hot if you enjoy having eyes.
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.
My Mishimoto thermostat died on day 3, if you have one that might be the cause.
Otherwise
The stock ECU , depending on your firmware cuts the fans when the car is moving very slowly. If you are missing the plastic undercarriage, you need to edit the ECU to not disable fans until you reach highway speeds.
I had the same issue with mine, my fans would not cut on until 210F sometimes. It was a problem when i was city driving only.
After flashing new rom, i run at 170F at all times, instead of a constant 200-210F.
Last edited by finalturismo; 12-13-2019 at 11:50 AM.
11-05-2019, 01:12 PM
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