Why did Mazda sell the RX-8 with an incompetent cooling system?
 

As the title suggests, exactly why?

I'm from Sri Lanka. It's summer all year round, averaging 95F. If it's over 90F outside, my car hits 220F when idling in traffic. The only way to drop the temps is to turn the AC off or drive it at 30+ mph for 2 mins. That would bring the temps down to 200F. Now I know this is bad. I know if it sticks around 220F for too long, it's gonna blow a coolant seal. Thing is, my car is new, with less than 2000 miles on the clock. I can only assume that this is how the car is! And it's not only my car. Pretty much every RX-8 on the island has this issue. They can't idle. Idling would make them overheat.

We know the temp needle is a dummy. It only starts to move when the coolant temp is over 232F. That's too late. Most people don't monitor the coolant temps in real time. They just look at the gauge and go "yep it's nice and cool. All good". You could be sitting at 228F and the gauge would still stay in the middle!

This brings me to the question. If the cooling system can't handle 90F weather, then why the heck did Mazda go ahead with it? What the flip flop were those engineers thinking?

Since this only happens at idle, does anyone have a workaround for this that doesn't cost big bucks?

Any thoughts on this issue are welcome guys.

The stock cooling systems works fine when it is operating correctly. I live in south Texas where we get over a 100 days of 100F weather and it is not an issue. As for the gauge, well it's a dummy gauge and according to Mazda the engine is safe up to 243F. There are many OBD II solutions if you want to see actual temps.

As for improvements, that has been discussed to death, search. But as I said, if things are working like they should then it should not be a problem.

If every car on the island has this issue, it's probably not just his car. We don't know what Mazda's cooling testing looks like, but the RX8 would have had to pass the same environmental conditions as every other Mazda. So question back to the OP: do all cars cook in traffic where you are?

Sitting in traffic is pretty much the worst case scenario from a cooling point of view, no airflow, and the airflow you do get is already hot from the car in front of you. And humid, I imagine.

Thanks for your reply 9k. Don't you have a BHR radiator with 3500cfm SPAL fans? I did read about the possible solutions. Bigger radiator, faster fans, lower temp thermostats and so on. Ive read that 220F is bad for these engines. I remember reading one of your posts about how hitting 220F often in the canyons caused your engine to blow a coolant seal. You said you got it in an oil sample :)

I've done my reading. My car is a 2012 with 1800 miles. And it's not only my car. Every car over here runs hot at idle. They cool down when driven over 30mph for a min. So it's not just my car.

Yes I'm checking my temps with an OBD2 scanner. Hits 220F after 30 mins of being stuck in traffic, in 95F weather.

Loki, exactly! EVERY car has this issue up to some extent. They just don't know it, because they don't monitor their coolant temps with an OBD2 scanner. Yes the climate over here is pretty humid. Almost 100% humidity. I've read here that a hot humid climate is better than a hot dry climate for a car? I don't know for sure, but what I do know is these cars are dying over here, and nobody seems to know what's wrong with them.


I thought I'd start this thread to brain storm any ideas to fix the issue that WONT BREAK THE BANK. So a big BHR radiator is a no no. I cannot afford to drop $500 on a BHR radiator after paying 200% import tax to bring down the car.

No I don't have the BHR radiator and I am turbocharged so it's a whole other world. More powerful fans will help, a different thermostat is a waste of money. And no, driving in the canyons didn't cause my coolant seal to fail, I have done that for years and the only time I overheated was when my belt broke at 9000RPM and of course it overheated within seconds. But it ran fine for a year after that. My builder said it was more than likely due to poor assembly based on the amount of silicone that was used where it shouldn't have been used. And yes the coolant leak was discovered in an oil sample.

220F is well within the limit of safe in traffic with no air flow. And most track guys exceed that, even with upgrades you will exceed that occasionally. Now if you are constantly at 220F all the time then that would not be good but an engine is not designed to sit in traffic all the time, it needs cool down cycles or everything will heat soak. Most cars normally run around 215-220F in terms of coolant temps.

If you constantly sit in traffic then the FAL fan upgrades and lowering the fan on temp would go a long way in helping with your issues.

Cars don't care about humidity. They don't perspire like animals do to get rid of heat.
I don't get what makes you think the cooling is not good enough. There is no way your engine is blowing a gasket at 220F.
If every RX-8 overheat while idling at 95F ambient, Mazda is gonna have a big issue.
Normally 190F is when the thermostat opens and around 210F is when the fans kick in.

"Why did Mazda sell the RX-8 with an incompetent cooling system?"

That question is quite misleading. Tantamount to me asking "Why do you beat your wife?"

My bad :) You had a Koyo radiator, which turned out to be worse than stock. You then ditched it for a stock radiator I presume? You are the reason I’m not swapping out my stock radiator haha. You had mentioned in one of your posts that constantly hitting 220F is bad for the engine, and that it will eventually lose a coolant seal. I guess that post I saw was older than the story you just told me. It didn’t mention how the belt snapped, or how your builder said it was due to poor engine build quality :)

Yes I know a lower temp thermostat is pointless. Doesn’t matter when the thermostat opens if the system isn’t powerful enough to maintain that temp.

You say 220F is normal. But everyone else here says 220F is right about when you start to lose a coolant seal. This is why I always try to keep the coolant below 215F.

I mostly drive around the city. Traffic in Colombo is terrible. If I’m stuck in traffic for more than 20 mins, the car’s coolant temp slowly starts to rise. Turning off the AC drops it down to around 200F.

Getting the fans to turn on earlier won’t help, because I have the AC on, and the AC forces fans to go on full speed.

You're correct! Cars don't care. It's just us haha. I just brought it up because I don't see anyone else complaining about their cars overheating in a humid climate. I think the cooling is not good enough, because it really is not good enough. I've read on this forum that 220F is bad for these engines. That's why I try hard to keep it below 220.

Every RX-8 on the island cannot handle idling for more than 10 minutes. Yes. 10 minutes is enough to get the coolant temp over 220F. I was in a friend's R3 the other day, and we were idling for about 15 minutes. The coolant temp went up to 226F! We had to turn on the heater to get it down to 220F. It's not just my car Jason. EVERY car on this island has this issue. And I highly doubt the cooling systems are failing. Most of these cars have less than 20,000 miles.

I had an OEM replacement Koyo/Calsonic plastic radiator that I installed when I broke the nipple on the OEM one, I never had any issues with it, I just upgraded to the Mizu aluminum one because I got it free. The opinion on the 220F damaging the stock coolant seals came from my builder based on what he has seen but it is just an opinion, I have seen plenty of guys here in Texas and in AZ, GA, etc that exceed 220F all the time and never had an issue so take it for what it is worth. Personally I think 220F is ok, but when you start getting above 230F then you should start thinking about pulling over and letting the engine cool down.

I also run Evans waterless coolant. Turning the fans on earlier may not help much with the stock fans but the FAL fans flow, even with the 420 setup. The 490 flows even more. But if you have a 2012 then you already have the upgraded radiator and fans that come in the Series II RX-8's. But if all your driving is in heavy traffic then there is only so much you can do since rotaries will heat soak.

Thanks 9K :) I'm so scared of screwing up my engine, I always try to keep it below 215F. I've heard too many horror stories. Your builder's story included.

Trust me, I'd love to have the FAL 490 fans. I just can't spend $400 at the moment. The other reason I refuse to swap out the fans is because I'll have to take the radiator out, and that will most definitely break that damn nipple lol. Then it'll be another $500. I can't take that risk right now.

Yeah that's the thing. My car is almost new, with a perfect cooling system. If this cant keep the temps below 220F, then the stock cooling system is not powerful enough. Sometimes my car would hit 222F. I actually don't know where it maxes out because I turn off the AC when I see 220F. I have a Mazda 3 and I've never seen it go above 210F, ever!

See, me and my buddies over here in Colombo have come up with an idea that should, at least in theory, fix the overheating issue.

Since this is only happening at idle, when the whole cooling system depends on the airflow of the fans, what if we fix an additional fan on the front of the AC condenser to push air inwards? It'll be a "push-pull" system. The fan on the front of the condenser will be sucking air from the front of the car and pushing it into the radiator, and the stock fans behind the radiator sucking the air into the engine bay that's forced in from the fan on the front. I've seen a lot of cars with auxiliary fans on the front of the AC condenser, so in theory this should work.

What do you guys think? Has anyone do this?

I think we should change the title to "Why did nature build an island with such an incompetent cooling system?"

I think you're better with bigger puller fans than push and pull fans. The more things you add in there the more you're messing with the airflow at speed.

LOL. Lets not blame 90F weather now. We all know the RX-8's cooling system is a little weak. Yeah it will mess up the airflow at speed for sure. But I don't think it'll be too bad. I'm trying to avoid doing bigger puller fans because it's going to cost a lot. The other reason is, to fit those fans I'll have to pull the radiator out. That could break the radiator nipple.

I was browsing some mustang forums and some say it really helps, some say it didn't change anything. Has anyone done this to an RX-8?

You can pull the radiator without breaking the nipple, you just have to not take that hose off the radiator and disconnect it at the coolant reservoir. Yours is a 2012, I doubt it is that fragile yet. As for the price, well if you want an improvement you have to pay for it. Pusher fans is a bad idea, no need for that.

No kidding about the heat soak. After being stuck in stop and crawl traffic on a 100 F day for 30 minutes, my intake air temp hit 185 deg F! By this point I had the AC off, and my coolant temps were about 212-215 F.


To the OP, how old is the coolant in your car? What ratio of ethylene glycol/water are you running? Running a lower percentage of ethylene glycol should help a little bit, and freezing is obviously not a concern for you. You still need some minimum % of coolant for the anti-corrosion additives (30%? can someone chime in?)


Here's a website with some basic fluid properties for ethylene glycol solutions:
Ethylene Glycol Heat-Transfer Fluid

I have a Series 2 car and live in North Texas, where we have temps above 95 for at least 3 months in the summer and temps above 100 for at least 1 of those months in most years. We also have a lot of traffic here during morning and evening rush hours.

My car behaved much like yours before I upgraded my radiator to a Koyo HH and changed my coolant ratio. It never bothered me too much, however, as the fans would keep it from going much over 220F or for very long. There are hundreds, if not thousands, of RX-8s running around up here as daily drivers, and none of them seem to be having any actual problems with the heat during the summer.

Having said that, I think you may be hung up on a false premise. 220F has been reported to be problematic by one engine builder. He is entitled to his opinion, and he may be right, but anecdotal evidence of RX-8s doing just fine in the heat is all over the southern USA. And, Mazda says the engine is much more heat-tolerant as well.

Tracking a car introduces another set of variables entirely, and that is why I upgraded my radiator. My goals were to reduce my peak on-track temps by a few degrees, decrease recovery times through increased efficiency, and move away from the plastic tanks for increased reliability under severe driving conditions. As a bonus, I gained about 2 quarts of coolant and had the opportunity to optimize my water to EG ratio for my climate (I don't drive the car when it is under 50F outside, because I only have extreme summer tires). You can read about that process here.

While I realized some measurable improvement on the track, I see very little improvement on the street while sitting in traffic. It takes a few minutes longer to heat soak, and it cools down a little faster when I start moving faster than 30mph or the fans kick on, so that is something, but max temps are only a little lower than before. That's better than nothing, but it isn't huge. The CFM over the radiator fins seems to be the limitation. At this point, I have no plans to upgrade my fans, however.

Something that has helped me cool the car down before putting it in the garage is the fans on low mod. This easy mod allows you to make sure both fans are always running at least on low speed (or medium if you like) regardless of what the ECU wants to do. This probably doesn't do anything when you are sitting in traffic with the A/C on (see fan control description below), but it does seem to affect cooling when the car is moving more than ~10mph, but too slowly to force much air through the radiator, and when the A/C is off.

https://cimg2.ibsrv.net/gimg/www.rx8...fd37312fbc.png

That's brilliant. All this time I thought you have to take that hose off to get the radiator out. I know that 1 pusher fan on the front is not as good as 2 fast puller fans on the back. But I can get a pusher for a really low price. That's why I'm considering it. Do you have any experience with them to say it's a bad idea? A 10F drop is all I'm looking for.

Whoa. I haven't monitored my IATs, but I'm guessing it's similar to yours. Do you have a series 2? What was the temp with the AC ON?

The car came with stock Mazda FL-22 coolant. I thought of that too, so I swapped it with Wurth coolant and mixed it myself to get a blend of roughly 30% coolant and 70% distilled water. That did not help at all. I think lowering the amount of antifreeze in a system and increasing the amount of water is bull. It doesn't seem to lower the temps. At least not in my case.

Thanks for the detailed reply Steve. I have read a few of your posts. You said your car didn't exceed 215F in traffic. Now you're saying it went well above 220?

So the 220F story was started by one guy, and then everyone started saying it?

I will never track my car, so I guess a bigger radiator is going to be overkill. Even with your Koyo rad, your car hits 220? Mind posting some before and after temps? :)

It seems that the stock fans aren't spinning fast enough to cool the car at idle. That explains why the temps drop considerably when moving at 30mph.

I have seen that diagram before. From what I've heard, the fans on low mod is a restriction to the cooling system when you're moving fast, because the fans are spinning slowly, acting as a blockage for the air coming through the radiator at speed. That said, my car once went into some kind of safe mode and had the fans on high all the time, and it drastically dropped my temps! Not when idling, but when moving. So I guess you're right.

In my opinion, Mazda should've designed the car to withstand at least an hour of idling in traffic. I don't want to plug my scanner 30 mins into the traffic jam and see the temp at 226F. That's scary stuff. My Mazda 3 can sit in traffic all day, every day, and never see 210F. I know these cars put out a lot of heat and these engines can't take heat very well. Mazda knows that too! They should've fitted faster fans. Fixing a cooling system that's not in optimal condition to withstand a traffic jam is one thing. Upgrading a cooling system in a new car, because it came with a weak cooling system in the first place is something completely different.

216 was the nominal high once heat soaked in normal conditions. I have seen around 220 peak a couple of times in 3 years in extreme conditions (ambient temp > 105). Sorry for the lack of clarity, but I didn't feel like typing a thesis on my car's temps, so I lazily used your number.

The fans on low can become a restriction at speeds above 30mph, which is why I put mine on a switch. I turn them on when sitting in traffic and when creeping through residential areas at 15-20mph. I also turn them on when exiting the track and driving around the pits and paddock. I only plan to use the fans in the summer here. It is an easy and almost free mod that may help you in certain conditions. You can wire up a switch and tie it up under your dashboard to test the mod and see if it works for you without doing any permanent damage to your car. You can also wire them to run at medium or high if you like, which would effectively simulate a fan upgrade.

I still think you are operating under a false premise here. Most 8 owners who live in hot climates pay no attention at all to their cooling systems while driving them all summer long in high to exreme heat and have no heat-related problems. Also, keep in mind that the membership on this board is mostly enthusiasts and people having problems. That does not accurately represent the 8-owning public at large. Most 8 owners have no idea this board exists.

Hi yes it is, all the cars hear is a pretty much the same last Saturday when I was idling my car temp rised till 232F

I'm not familiar with that coolant, is it
FL-22 compliant?
I don't recall the chemical, but there is something in most of the typical coolant brands that is harmful to the Renesis.

Replace your radiator, coolant bottle, cap, coolant lines, and thermostat, and I bet you will see an overall reduction. I'm guessing you have a 2004 or 2005, and if any part of your coolant system is original, it is 10-12 years old.

BigCajun, it's 2-Ethylhexanoic acid. Better known as 2-EHA. The Wurth coolant I got does not contain 2-EHA. So it's all good.