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RX8's temperature (overheating).

Old 05-20-2016, 12:03 PM
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Question RX8's temperature (overheating).

Hello, so I have been having issues again with my RX8 overheating. Does not surprise me though, as it is hitting summer-weather in Florida (it gets HOT as HELL) . However, I see a lot of posts with different solutions and opinions on it.

First of all, I will be changing the thermostat, and performing a coolant-flush, but I also want to check what oil would do me best for hot temperatures (streets in Florida can reach up to 155 degrees farenheight, specially when stuck in traffic). With the AC on, overheating is almost inevitable. But besides the things that I will do, what other good options are there? (I will not be changing the radiator, because I recently changed it), And what oil would do me best?

I am currently using Castrol Oil 5w20, yet I have heard that thicker oils such as 10w30 could protect the engine better (this is the same oil my dealership was using). Also, what coolant or coolant-mix will keep my car at good running temperature, and help me avoid the risk of overheating?

Hope for your solutions,
thank you.
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Old 05-20-2016, 12:12 PM
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Luiss:
I would recommend using something closer to 70/30 (water to coolant) ratio.
As for oil, our little fire breather motors will run on just about anything you put in them so bumping up to 10w-30 might be a good plan.
I haven't used 5w-20 in years.
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Old 05-20-2016, 01:47 PM
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A thought...

Check out the congrats thread below. There are some things that will help keep her cool. Thermostat just adjusts the point that overheating starts, unless you have a bad one. The cooling mods in the congrats thread will help, especially foam and fans on low.

The read https://www.rx8club.com/series-i-tro...o-i-do-258334/

Let us know how it goes. My old one would sit in an orlando parking lot, in 95 degree weather, with AC on full, and run at 185 for an hour.
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Old 05-20-2016, 04:29 PM
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Hi 04Green, yes; I am changing the thermostat because I am confident its what is causing the car to overheat quickly, I had the radiator changed before, and the people that did it did not change the thermostat with it. Also, thank you for the other recommendations, I have heard so many times about the foam. Do you have any recommendation of which one I should buy? A direct link will help me a lot. And also, where should I put the foam on?

And about the fans on low, why on low if I am trying to keep the temperature down?
Thank you brother.
Originally Posted by 04Green View Post
A thought...

Check out the congrats thread below. There are some things that will help keep her cool. Thermostat just adjusts the point that overheating starts, unless you have a bad one. The cooling mods in the congrats thread will help, especially foam and fans on low.

The read https://www.rx8club.com/series-i-tro...o-i-do-258334/

Let us know how it goes. My old one would sit in an orlando parking lot, in 95 degree weather, with AC on full, and run at 185 for an hour.
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Old 05-20-2016, 05:13 PM
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Might I suggest you hook up a BT OBD II and marry it to your smartphone for some engine telemetry. Understanding your coolant temperature at various state of drive conditions would give some intelligent insights. Then plan your actions from there.
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Old 05-20-2016, 07:28 PM
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Here is a re-post of my thoughts on overheating from another thread:

I need data logs to remotely diagnose your situation. What you are saying about the temp gauge is troubling, however. It doesn't move from the center until you are already very hot (235F if memory serves). That points to overall inefficiency in your cooling system that could be due to one big failure or several small failures combined. My coolant temp never rises to more than 215F on the track in the hot Texas summer. Under normal spirited driving around town, it never rises much over 195F.

Fans

The fans in this car are known to weaken (slow down) over time. Yours are 12 years old, so they are worth testing for RPM and current draw.

Water Pump
The early water pump design was known to suffer from cavitation at high RPM. Mazmart solved this with their aftermarket Remedy water pump, and Mazda redesigned their pump at some point. So, again, at 12 years old, yours is worth looking at, as it could be the early inefficient design.

Radiator Foam
The radiator should have some heavy foam on the bottom and light foam around the top and sides. The foam is designed to force more air through the radiator at low speeds and allow some air into the engine compartment at higher speeds. Some guys advocate stuffing more foam all around the radiator to force as much air as possible through it. It will lower your coolant temps when the car is moving, but it will also raise your engine compartment temps, which is not good for the rubber and plastic in the engine bay. If everything else is working well in your cooling system, this treatment should not be necessary, IMHO.

Radiator
The proximity of our radiator to the ground means it gets dirty faster than radiators otherwise do in other cars. I have found back-flushing the fins with clean water to be worthwhile. Clean the oil coolers while you are at it. And, be sure to straighten all the bent fins you find in the process.

Thermostat
In a 12 year old car, the thermostat may not be opening completely. It is an inexpensive part that is relatively easy to change. You also have the option of buying an aftermarket 170 degree thermostat that will begin to open 10 degrees sooner to help combat heat soak.

Catalytic Converter
What? Seriously. The cat is prone to clogging and preventing heat from effectively escaping the engine. This can put additional strain on the cooling system. It should be inspected.

If it were my car and my wallet, I would bite the bullet and refresh the whole cooling system just to be sure. I would replace the radiator since it is partly made of 12 year old plastic (an OEM style replacement is only $90), replace the water pump with an OEM unit, replace the thermostat with an OEM or Mazmart 170 degree unit, replace the accessory belts, and flush and replace the coolant with genuine Mazda FL22. I would test the fans and replace if necessary. I would also inspect the cat for any signs of clogging.
I like to run a mixture of FL-22 coolant that works out to 60% distilled water and 40% coolant. You need a certain amount of coolant to lubricate the water pump.

Be aware that this car requires coolant that is lacking certain additives that damage silicone seals. It is best to stick to Mazda FL-22, which doesn't really cost much more than Prestone or whatever anyway.
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Old 05-20-2016, 11:59 PM
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Very complete answer. Well, looks like there is another good reason for removing the cat.

Originally Posted by Steve Dallas View Post
Here is a re-post of my thoughts on overheating from another thread:

I like to run a mixture of FL-22 coolant that works out to 60% distilled water and 40% coolant. You need a certain amount of coolant to lubricate the water pump.

Be aware that this car requires coolant that is lacking certain additives that damage silicone seals. It is best to stick to Mazda FL-22, which doesn't really cost much more than Prestone or whatever anyway.
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Old 05-21-2016, 09:38 PM
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As far as oil is concerned, you can read the 13 years of oil wars for yourself, or you can settle for this quick summary. Synthetic seems to be better. (Mazda USA says no, but Mazda everywhere else recommends it. Used oil analysis proves it is superior.) Heavier weights seem to be better. (Again, Mazda USA pushes lighter weights for gas mileage reasons, but Mazda everywhere else recommends 30W, and used oil analysis proves it to be superior.) The Renesis is incredibly good at viscosity sheer. The most important thing, far beyond what oil you choose to run on any other basis, is that you change it frequently, no matter what oil it is. Three thousand miles is considered to be the safest and best interval. One of the perennial favorites is Mobil 1 0W40. Any 5W30 is also fine. Since you live in FL and don't have freezing temperatures for the most part, 10W30 or 10W40 will work for you. Some people in warmer climates use 20W50 with reported success.
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Old 05-21-2016, 09:52 PM
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Having written all of that, this is what I do for oil.

I take it to the dealer every 3 to 5,000 miles and request 5W30 oil. They use Castrol GTX and (hopefully) the correct OEM filter. I do this, because my car is still under its powertrain warranty, and I want the paper trail of regular oil changes to prevent any potential future hassles. And, with a coupon, I can get it done for around $20-25, which is far less than I would pay for an OEM filter and any retail oil if I were to do it myself.

I run on that until after my 1st track day on that oil change (usually 1 per month). Then, I drain and fill it with Mobil 1 0W40. I top off with Mobil 1 0W40 until time to take it back to the dealer before 5,000 miles have elapsed.

IMHO, YMMV.
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