I was in the middle of removing components to replace my A/C high pressure line. All the work up until now has been done by someone else or the dealer. This is the first time I have taken a serious wrench to this car. Not that I don't know how, just did not feel like it. I was removing most of the top components battery, air cleaner, coolant reservoir, and this is where the problem began. I hardly touched the thing and snap, that nipple on the radiator broke off...great, now in addition to the line, I need a new radiator. Also notice that the fan is a little stiff on the drivers side, so what the hell order the fan motor to. Seems no one stocks the radiator, not even Mazda. So I found one at 1800 radiators. Not my first choice, but at least I can put the car back together, get it off the jack stands and put it back in the garage.

I put the car back together evacuate and charge my A/C system. A/C works about as well as it ever did, now I just don't have to put refrigerant in it every time I want to use the car. At idle the cars cooling system works relatively well. If it does not move it will maintain 183 to 187 degrees in 96 degree weather with no problem. Problem is the drive. I have Aftermarket gauges and I measure the coolant temps via the RB adapter on the heater core supply line. The temps measured by the OBDII sensor is about +/- 2 degrees and that increases to about +/- 4 degrees up to at least 212F. The OBDII is always the lower of the two. At 75 MPH 96F A/C on, engine temps will climb to about 216 degrees before I panic slow down turn on the heater and the coolant temps will dip fairly rapidly. I test drove the car for over 200 miles to test it (not necessary I know). Basically I can drive, but I can't have any fun. So here are a few questions to go along with this novel.

1. I know I purchased a cheap radiator, which I will remedy in short order. I want to know if some of the after markets racing units really better than OEM. The OEM unit cooled the car just fine. However if I am going to pay $480 for a radiator I may as well spend another note and just get a great radiator. However I really want to know if its worth the extra cash. If I understand the concept correctly the racing units are built for capacity and will cool as well as OEM just under more stressful conditions. Yes I read some of 9K's long thread about radiators.

2. The radiators look exactly the same, minus the foam, which I removed from the old and placed on the new one. Could the build quality be that different that cooling performance suffers that dramatically. I did not remove the bumper from the car, so all the foam is still intact in the same places, and I ensured that the under tray is secure, it's got to be the radiator?

3. Based on the information offered here do you believe it is radiator issue or possibly something else I may have done, or failed to do.

4. I have not been able to find a definitive answer. What is the max Coolant temp before engine death. I read 220F where I am measuring from?

Lesson for others....don't buy crappy radiators for the 8. I have a gauge so I can see what's happening. If your relying on that stupid gauge on the instrument cluster you may have killed an engine.

2004, no engine mods 80k on the odometer. 19k second engine.

 

Lesson...don't buy crappy anything for the 8.
Just to get the ball rolling...
I have no first hand knowledge, but I've read a few good things about the BHR one.
I'm sure others will chime in.
Good luck!
* edit* Did you try a new thermostat?

 

about 120-125 Celsius is almost guarantee engine death.

but to get there, you gotta have shitty cooling with shitty coolant + going uphill pushing it to the limits.

the coolant temp on the car depends heavily on your thermostat, to get to optimal performance, the coolant should be around 170~180 to 200 degrees.

Your Radiator might not be the problem, stock(or stock like) radiators is just a plastic/aluminum that's so simple to make. I would wanna do I use the correct coolant mix and MAKE SURE you bleed all air out of the system.

something most people misunderstand is that, an Aftermarket "performance" radiator will make their coolant temp lower than OEM Radiator. As stated earlier, the temp is controlled by your thermostat. Mazmart sells a thermostat that has an earlier opening temp (76 Celsius). So the rad will cool your coolant "Earlier", but 76 Celsius is the lowest it can go.

 

I have an OE radiator and fan assembly available in near perfect condition if you are in need.

Let me know?

 

Thank you for your input. The Coolant is the stuff Mazda sells. 55/45 mix and says not to mix it. Purchased two gallons from them. I am wondering about the bleeding procedure? I may not have performed that correctly. I will have to go back and re look at that procedure. Thanks for the insight, that may be the problem, at least I am hoping it is. The current Thermostat is 180F. I have never wanted it too low. As much as I have read about getting this engine warmed up, that seems kind of self defeating. Before the radiator change I would hold 197F at highway speeds over 80 with the A/C on on a 90+ degree day.

As I stated earlier the only reason I was interested in the "performance" radiator is because of the cost of the stock unit. If I can spend a wee bit more and get a better unit...why not. The "kill" temp you quoted seems high and makes me wonder what was the problem with some of the "overheated and dead" threads I have read lately. According to your numbers I should not be concerned at all. I still would be more comfortable with temps below 200 while cruising though. Thanks again!

 

I just paid Mazda $230 for a new fan motor...Where were you last Wednesday!

 

I was here with an add in the F/S section

https://www.rx8club.com/rx-8-parts-s...r-fans-247297/

 

ME and OP might have the same problem. I don't have an AM gauge, as I am poorish and that isn't the first mod on my list at the moment, but my engine temp will do the same thing.

My story - A month ago my thermostat got stuck or something happened to make my engine temp sky rocket and my coolant overflow. I was on the HW and some coolant was still in the reservoir so I put some bottled water in there to hold me off till I got where I was going. Idk how full it got the coolant tank or what the mixture ratio between the AF and water was, all I know is that I got to work on time and didn't get in trouble. My problem ended there and never occurred again. Out of precaution I replaced the cap and checked for leaks and saw nothing. Today we went and got a thermostat and had the whole system flushed so I'm hoping my problem will stop. Ill be leaving to get my car in about an hour. What happens to mine is that I will crank up, get going, and if I leave it around 5k rpm for too long it will start heating up. It won't cool down until I ease up or turn the heat on. So just like you said, I can't have fun for now. I can easily just cruise around but that's it.

By the sounds of it, MAYBE it has to do with air in the coolant. Or bad thermo? Let me know if your find something. I will post up my results when I get my 8 back.

 

Just so you guys know, s1 stock water pump gonna having something called cavitation after 6000 rpm, when that happens, ur water pump does not pump water, its just making bubbles. Which is the reason why temp goes up after 6k rpm, mazmart sells a pump which helps this problem

 

Im aware, but Ive never had this problem to this extreme. It gets way hotter than it should. Like dead engine kind of hot.

 

Well bled out the system per the DIY. Actually there was nothing to bleed out. Coolant started spewing out of that sucker soon as I took that line off. Now that I know it has been bled properly, the only other variable is the radiator itself. All in all I basically have approx a 20F degree increase in running temps since the new radiator. Based on some more reading I am pretty convince that 220F is where you should start paying attention. 230F is where you should be really concerned. Based on the condition of the motor, coolant condition etc etc. 235F and above you are about to invest in a new engine or trade it in after it blows. 240F is terminal. I have learned that when you rebuild them that you can buy more durable coolant seals. If it ever comes to that I will definitely take that option.

Now I just need to decide what I want to buy. Stock, more than adequate for my needs. Racing, just for a little extra piece of mind. I'm in no hurry especially with fall just around the corner. Besides it will sit in the garage for weeks until I get in a mood to put it on anyway. I'll keep reading and decide what I want to get. Thanks for the help!

 

As for the coolant seal, sure the HD seals (it's really just Mccar viton seals) might be able to survive a heat bake, but your engine wont, housing will most likely warp, and there is a chance of leaking (unlike stock which is squared, the HD aftermarket seals are round)

it's a personal preference really, but for me I will just stick with stock and just apply some hylomar to help it seal better (even last longer than HD water seal in some cases), sometimes it can hold water even the telfon/rubber seal is broken. at least for a while.

 

Update: For those who give a damn lol.

Well after some extremely focused reading, I decided to attempt what I have seen a few others do according to some older threads. I had some Styrofoam in the attic that has been there for years with no specific purpose so I said what can it hurt, it's not going to cost me anything more than time. So I pulled the bottom tray and started cutting Styrofoam sheets into custom shapes to close all gaps between the sides and the bottom of the radiator. This was in place of the stock foam that is supposed to do the same job. Given that the foam was old and I removed and placed onto the new radiator, I just had a hunch that it could potentially be the problem. Given the effort taken by Mazda to direct airflow in a specific direction given the odd angle of the radiator. I figured this was worth a try before spending money on a new radiator to end up with the same result.

So I make all of my custom pieces, button it all up and take her for a test run. I pull out at 160 with the air on, outside temp is 96F. I have to get fuel, so I leave it running. Temps hold at 183 while fueling. While on the surface roads I get up to about 195, which is already a better situation than before the foam. I get on the Highway WOT. Temps climb to 210 but as soon as I stabilize my speed the temps begin falling off pretty rapidly. I won't go into the whole test run, but needless to say the performance of the cooling system has seen a dramatic change. It's not as good as the stock radiator, but not too terribly bad either. I am now about 5F degrees hotter than before the switch. I believe that if I get back under there and refine what I have now, I can meet OEM standards, but I am satisfied at the moment. So turns out you probably can not reuse the stock foam, if anyone has and has been successful, post up.

Glad this is behind me, I could not rest until this was resolved. Now I can give her a tune up and change the oil. Thanks to those who helped get the cogs in my head spinning.

 

Update on my situation - FIXED!


We flushed the coolant and threw in a new thermostat and now it's back to normal! :thumbs: