Does your car have the stock fans? How about idling in traffic for long periods with AC on? That's when my car starts to go past 220F.

 

Have you tested it? I put the OEM and RE-Medy thermostats in a pot of boiling water and the RE-Medy opened substantially further. I could have sworn I took pictures, but I'm unable to find them on my phone. I'm charging up my previous phone as they may be on there.

 

Perhaps I would have seen the same temperatures with a new OEM radiator, thermostat and coolant. However, it wasn't my experience with the original parts on this car, or on my previous RX-8. I definitely saw higher operating temperatures in the peak temperatures here with the OEM systems. In my old car, I saw a peak operating temp of 223F, when ambient was 117F while stuck in traffic in Phoenix last year. (That sucked some sweaty *****). I think that is essentially a worst case scenario for a car not being raced.

Possible reasons my data is different from your experience:
1) Maybe my OEM cooling components were not up to snuff in both RX-8s, despite them not overheating.
2) Peak temp here since conversion = 115F. San Antonio = 104F (since 2004 as far as I see).
3) Evans coolant supposedly causes engines to operate at a slightly elevated temperature (I've seen reports from 0-40F increase. I can't definitively comment, since I changed other components at the same time, but the car is running cooler than it previously was.)

YMMV. I'm not selling this. I think they're fairly expensive for a thermostat. I don't think I would recommend one for a normally driven car in a more temperate environment, but I had a particular situation where I wanted to try it (waterless coolant and OEM radiator). I would have maybe upgraded the radiator in lieu of the thermostat, but at the time SCCA Solo STX rules did not allow for an upgraded radiator. Of course that changed moments after installing the new OEM one!

 

You should really learn how the thermostat works, I'd think that replacing one and testing one would give you some idea but I guess not.

The thermostat housing sits on top of the hot side and cold side coolant channels from the radiator. The hot side is filled with hot coolant coming out of the front of the engine after being circulated through it, while the cold side is generally filled with cold coolant coming out the radiator. Directly underneath the thermostat there is a hole that connects the hot side to the cold side.

When the coolant is cold (thermostat closed) the hole is open and coolant is allowed to circulate from the hot side (from the engine) straight to the cold side (into the water pump inlet).

When the coolant is hot (thermostat open) it plugs that bypass hole, forcing hot coolant from the engine to flow through the radiator before reaching the water pump inlet.

This behavior allows for the engine to warm up more quickly because the thermostat can force coolant to recirculate through the engine until it reaches the operating temperature. That being said, a thermostat that opens more when tested isn't going to change how much flow you're getting. These thermostats just push up against a bypass hole until it's fully closed, you can't make a fully closed hole "more closed" and expect it to be better.

 

Despite your snide opening and detailed explanation of the cooling system, you seem to have overlooked the fact that the radiator valve regulates the operating temperature of the engine, not the bypass valve. So, I don't think it is myself who has a lack of understanding. Here is how I understand it:

In the thermostat, the two sealing faces for "radiator" (the one with the rubber gasket) and "bypass" valves can move independently of each other, because the bypass valve face can slide on the piston shaft. So, while the bypass valve can get no more closed than closed (as you said), the radiator valve can continue to open further after the bypass is closed. Check out the pics I just took with the OEM thermostat in the cold position. It functions the same way when hot, except it burns my hand Note the radiator valve is in the same position in the first two pics, but the bypass valve is in two different positions. Hmm...

Here are some potential scenarios for the engine:
-Engine is cold, bypass valve is open, radiator valve is closed.
-Engine warms up to around intended operating temperature, bypass valve closes and radiator valve is open some amount.
-Engine temperature increases from intended operating temperature...NOW WHAT? Since the radiator valve can move independently of the now closed bypass valve, it just opens a little bit more to allow coolant to flow more freely to the radiator.

If this independent movement of the valves was not possible, as in your explanation, the engine would have no further ability to cool itself once it reached the temperature at which the bypass was closed, except via increased airflow through the radiator. The OEM fan settings are 207F and 214F for Fan 1/2, and have their hysteresis set at 37F. Operating temperatures don't fluctuate that wildly and again...if operating temperatures continued to increase over 214F there would nothing else to increase cooling on the engine and temperatures would continue to climb, but this isn't what happens if the cooling system is in good shape.

If you don't believe that's how it operates, check out the third pic (sorry, it's slightly blurry). I removed the bypass valve disc/spring and you can see the wear mark halfway down the exposed portion of the piston shaft where the bypass valve sits during normal operating temperature conditions. So, the bypass valve is clearly closed while the radiator valve keeps opening, pushing the piston shaft through the bypass valve and typically sitting at this point, but the radiator valve could open another 1/4" or more beyond this.

So, again...I tested the RE-Medy thermostat and it opens further than OEM when placed in a pot of boiling water. As far as I see it will open further in the car at this same temperature as well. Thanks for putting me in my place, though.

 

Calm yourself, I wasn't trying to be snide but apparently you're sensitive.

I know what you're talking about now, but making that opening larger won't increase coolant flow in any usable capacity. It's physically impossible since that opening isn't even close to the biggest flow restriction.

 

Convincing recharacterization of your tone, really. Lol

In any case what opening are you speaking of making larger? Are you saying that allowing the radiator valve to open further won't allow more cooling? That's exactly how it functions. More open = more flow to radiator = more cooling. And since that valve is what controls the flow, it seems it must be the point of most restriction, by definition. I'm honestly not seeing where there is more of a restriction. What am I missing?

 

Yes.

 

Sorry about the delayed reply. It has stock fans, but I have lowered the turn on temperatures to 170 and 180F for Fan 1/2. I really don't get stuck in traffic much here, but after a hard drive and letting it idle for ~5-10 minutes with the AC I was at 208F, and you can see that was actually down from the peak of 210F. The dash says 112F, but the official temperature was 115F, and my wife's car parked right next to it said 117F. So, hot one way or another.

What ambient temperatures are you seeing when you get to 220F? If you have your original radiator, I would replace it since they can accumulate a thin later of oxidation inside which inhibits heat transfer.

 

It happens when I'm stuck in traffic for over an hour. The car gets heat soaked to the point that the stock fans simply aren't enough to cool the car. Ambient temp is around 99F. When I start moving again, the temps drop. My car has only 3200 miles, so it can't be my radiator

 

That is quite low mileage, and I don't know what year your car is but a radiator that has been sitting filled with 50/50 water/antifreeze without ever being driven is still not going to be in mint condition internally, but since yours is not completely overheating it's probably fine.

The stock fans come on a 207F and 214F. I would suggest a COBB Accessport or Mazdaedit (your only option if you have a Series 2) to lower the fan temps and also increase the amount of oil that is injected via the OMP. I've read on here that the increased oiling makes a noticeable difference in idle temps. I only increased my OMP rate from OEM, recently (since I use premix oil), and I can't remember if it was before or after I took that pic of the high temperature here. haha

Another option if you don't want to go with the ECU reprogramming route would be premix oil in your gas (I hope you're doing that if you don't have a S2) and wire your fans to run at a lower temp or all the time. Additionally, you could get small fans to attach to the backs of your oil coolers, if you're stuck in traffic frequently. Lots of 7" ones on eBay. I know it some markets, some RX-8s only had one oil cooler...do you have two?

 

My car is a 2012 and I changed coolant last year. I don't think lowering the fan trigger temps will do much because when I'm overheating, I have the AC on. Having the AC on in this weather forces the fans to go on high speed. My fans are on high the second I start the car

Does increasing the amount of oil injected REALLY lower coolant temps? I thought that was a myth. No I don't premix. I've heard that it clogs up the fuel lines? and there's no solid evidence that it helps.

Yes my car has two oil coolers, even though almost all the S2 automatics I've seen have one
Yeah they're cheap and I wanted to do two small fans behind the oil coolers, but then 9k said it doesn't do much, so I ditched the idea.

 

Unfortunately, the guy you're talking to really just doesn't know enough to help.

Oxidation isn't going to be an issue on an aluminum radiator under stock flow. Aluminum alloys form a thin Aluminum oxide layer on them instantaneously when they come into contact with air. That layer is airtight so unless it gets stripped away (with really really high flow rates) it is permanent.

Increasing injected oil will in theory keep temperatures down due to decreased friction of the seals on the housings, but it is insignificant compared to the giant ball of fire that happens when the fuel ignites. You absolutely do not need to increase the OMP rates on an S2, the two OMPs pump in enough oil for any purpose on a stock engine.

Premixing will either increase or decrease combustion temps depending on how the fuel you're using burns (varies by brand and additives) and how the premix brand you're using burns (varies by brand and additives). The idea that it lowers engine temps is total BS and I have no idea how it got started, probably for the same reason as increasing OMP rates just not rotary specific.

The stock cooling system just can't deal with the heat loads that you need it to deal with when the AC is on. Good going on adding that second oil cooler, now we know that the issue is the coolant system's ability to shed heat. In an AT car all the heat from the Engine as well as the heat from the transmission is being dumped into the coolant, that's already a disadvantage you have when compared to an MT car.

When I went over my cooling system for the 63rd time I figured that one major contributing factor to less than stellar summer performance was the sheer number of loops that full temp coolant has that takes it directly back to the cold side of the pump.
I chose to take the two biggest of those lines (heater line and Coolant bottle drain) and run them each through their own separate auxiliary radiator. I further limited these loops by eliminating the Throttlebody coolant loop completely. I don't think that the cooler on the coolant bottle drain is doing much, however the additional cooling from the radiator post-heater core is significant.



This is the stock coolant plumbing, I wrote a little bit more about my process here.
https://www.rx8club.com/rx-8-discuss...3/#post4768335

For your setup I would recommend adding a single auxiliary radiator in series after the heater core and stacked with the second oil cooler in your oil circuit (preferably in front of it, but I don't know how that would fit in an S2 bumper). Unfortunately it can't be stacked with the stock radiator because what we're going after is an increase in effective radiator area.

Venting the hood might also be a solution, but with the stock battery and airbox positions there won't be much of a benefit.

 

Nisaja, I confess. He's right. I definitely don't know what I'm talking about.

I sure didn't prove him wrong on his various claims against the operation of the RE-Medy thermostat and bypass thermostats in general. It must be dumb luck that my cooling system is functioning at a quite acceptable level in essentially the same geographic region (we're both in Arizona, US it seems).

If I were you, I would get an aftermarket radiator, delete your factory oil coolers, get a 25 year old used oil cooler, and mount it in front of your aftermarket radiator to preheat the air that is being drawn through the radiator. Then, when you still aren't happy with your cooling system results, you should replumb your cooling system and add an additional radiator. That's definitely an elegant and simple solution.

It certainly is a lot less work than just replacing your thermostat with one that many people are happy with, and has a reasonable worst case scenario of being no better than stock. The only argument people have against it is that it won't help a car run cooler that isn't already maintaining the OEM temperature. This is a valid argument if it didn't open further, but it does open further and all the experiences with it I have seen are of lower operating temperatures. All the poo-pooing is by people who say it can't work, but I don't think have tried it.

I apologize for subjecting you to my sarcasm and derision directed at another. lol So, unrelated to that minor drama, I am assuming you're in Colombo (like your profile says) and from what I see online, the average high temp is only 91F (33C) there. That seems like rather low ambient temps for the operating temps you are seeing.

Since your car is so new, the cooling system is in presumably good condition. So, I can't really explain that except that the S2 water pump impeller is of a different design than the S1 and you have a larger diameter water pump pulley, meaning the water pump spins more slowly. The redesign of the impeller (and increase in diameter of the pulley) seems to have been to stop cavitation of the coolant at high rpm, but may have been at the expense of low rpm cooling. This might explain your increased operating temperatures. I haven't read much about S2 cars, if only because there aren't many out there and I don't have one :P

Aside from the RE-Medy thermostat, the next simplest and cheapest option might be oil cooler fans. Cheap 7" fans are ~$25/piece on eBay. Name brand ones, obviously more expensive. An aftermarket radiator may also help, but that's the most expensive and pesky to install of the three options.

If you have any other questions, feel free to PM me, but that's about all I've got on my experiences with RX-8 cooling. I don't care to spend any more time dickering with that know-it-all, so I'm unsubscribing

 

He lives in Sri Lanka, southern Asia.

The series 2 RX-8 has several improvements to it's cooling system over the S1 (better pump, stronger fans, and larger radiator). There are no known cooling issues when the system is working right on the street.

I had the Mazmart tstat and pump and neither did jack ****. We tried fans (rx8performance ones to be exact) on the stock oil coolers, didn't do jack **** to lower oil temps.

 

Running a totally heat soaked car there won't be much difference between thermostats if they allow the same flow through when they are fully open.

When a lower opening thermostat will help is the pre-heat soak situation when the thermostat is open part way. The earlier opening unit will divert more heat to the radiator sooner...and keep the car cooler for a while. Depending on the radiator and cooling capacity that might be enough to keep the car from heat soaking....and might result in the car overall running cooler

 

Guys guys! Let's not fight. We are a happy family!

Wow. Thanks a lot for the detailed explanation! Yeah I knew it was a myth, that's why I didn't mess with the OMP stuff. I didn't add a second oil cooler. My car has two. Weird, I know.

I had no idea the transmission heat directly affects the coolant temps. I completely forgot that it has a part of the radiator.

Yeah I guess I'm asking too much from the stock system. My car is weird. Today I took it out with a buddy and did a few sprints in traffic. Coolant peaked at 217F in 88F weather. And it didn't drop down! I had to idle it in the shade and it slowly went to 212F. Then again after 1 hour, ambient temp was 89F, the car hit 210F (again sprinting) and then dropped all the way to 203F while idling in the sun. So weird haha.

I'd love to get a secondary radiator, I just don't like the idea of messing with the coolant lines
I'm afraid I'll mess something up and ruin it.

Would an auxiliary AC fan help?? I've seen a lotta cars with a fan infront of the AC condenser. They push air inwards (towards the rear of the car). Wouldn't that assist the stock fans with shedding heat? I can pick one up for dirt cheap over here. I checked a few. Some spin as fast as the stock fans!

Lol, no worries buddy. Yeah I know the weather report says around 90F, but the car's ambient temp shows 98F at times. I think it picks up the heat of the road. The way my cars coolant temps behave is pretty funny. Sometimes it's 97F and I'm idling in traffic at 206F. Sometimes it's 88F and I'm hitting 220F. Very unpredictable. I assume it has something to do with the surface temp of the road. Whenever I pull into a shade, the temp drops down to around 199F.

I'm not sure if the S2 water pump causes the coolant temps to slightly rise at idle. I honestly don't know why this is happening to a reasonably new car. But a lot of fairly new R3s over here hit 226F while crawling in traffic. Most older rx8s flat out overheat. So it's not just my car. My temps are comparatively lower because I've done a lot of sealing around the radiator. Yes I know it's bad but I had a choice. High engine bay temps or high coolant temps. I chose high engine bay temps

I didn't get fans for the oil coolers because people said it doesn't do much. The lower temp thermostat isn't really worth it if the car can't maintain that temp. My car can't

Exactly why I didn't buy them.

 

Nisaja, there is a major drawback to higher engine compartment temps: heat degradation of rubber and plastic under the hood. The smaller plastic bits will become brittle quickly and start breaking on you. Think about all the little plastic clips, fasteners, holders, etc. They will only last a year or two with exposure to that additional heat. Your belts and hoses will also suffer. The extra heat can cut their lifespans in half. I strongly admonish you to remove the extra foam from the exhaust mainifold side of the radiator. Some airflow is needed there to draw the exhaust heat out of the engine bay and to create negative pressure that will draw other outside air into the engine bay in other areas. Also remember that the hotter your exhaust manifold is, the hotter your engine will be. That foam may actually be working against your goal of having a cooler engine.

 

Thanks Steve. I know it's bad, but I gotta admit, never thought about the belts and hoses. I've read on another thread a post of yours about not sealing up the passenger side. That area is sealed from the factory though. I will remove that side and see if it has any affect on coolant temps.

I was thinking of adding two small fans at the side air vents above the turn indicators. You think that would help lower engine compartment temps?

 

Aren't your passengers on the wrong side though?

 

I know. It's my drivers side. I just went with "passenger side" because I don't wanna confuse you guys :P

 

Since you have a repeatable high temp, will you run a quick test. pinch off the heater core return hose and see if your running temps drop. I have a working theory, but do not have a repeatable problem. Or, the next time it is hot and will not cool down at idle, pinch it off. See if temps drop.

 

Thanks 04Green, I'll try that. Turning on the heater makes the temps drop asap though.

 

^ Nisaja, if you are truly intent on fixing your coolant temp issues in traffic, your only answer is increased airflow through the radiator. I have proven that to you with data from my radiator upgrade and fan turn-on mod. You either need to do what is necessary to make your fans turn on at lower temperatures and/or at higher speeds, or replace them with higher flow fans. A heat exchanger can only exchange heat if there is a usable quantity of something with which to exchange that heat--in this case, air. You need lots of air, and driving in traffic does not provide much air. A higher flow rate from your fans is the remedy.

 

Yeah I've noticed that. If I'm cruising down the freeway at 60mph, the coolant drops to like 197F. It's only when I'm sitting in traffic. I'll have to get faster fans. Problem is they're so expensive.