I'm using a Cobb Accessport on my 2004 RX-8 6speed to monitor my coolant temps. When it's completely warmed up it read about 180-185ºF but yesterday on the interstate (about 90ºF outside) the coolant temps went up to 216ºF and stayed there until I shut the car off. There's plenty of coolant in the reservoir and the stock temp gauge didn't budge at all. Is this normal operating temperature? (my 8 has 82,200 miles) The last thing I want is an overheating engine and not knowing it. Thanks!

 

If you are on the stock thermostat, your cruising temp with constant airflow should be right around 190F. If you are idling, it will oscillate up and down based on whether the fan is on or not, but shouldn't get above ~205F or so. High ambient temps will make the upper value climb a bit, but a healthy cooling system should still keep them under control.

You may have a slightly failing thermostat, or clogging radiator, etc...

Might be time for a cooling system overhaul. About $400 for coolant, a new OEM radiator, and OEM water lines would go a long way. Getting the 172F thermostat from Mazmart is a common addition as well. This will just drop your target temp a bit, giving you some more headroom in some situations.

 

216 Is high, but it is okay. I'd backoff if it hits 220. Drive it some more and keep a close eye to see if the temps are staying up there or if it was just a one time thing.

You might want to check the front undertray to see if it is having problems.

Were you driving Hard? Were you in heavy traffic?

You might just take a pressure washer and wash your radiator good also.

 

It hung around 200 or so until I hit heavy traffic on the interstate. That's when it went up to 216. After traffic cleared and I was off the interstate it remained at 216 for the remainder of the 2 hour road trip. (driving under 4500 rpm the whole time)

I know it's time for a new cooling system altogether but if it continues to run at 216 should I expect any problems? Honestly cannot afford purchasing an all new cooling thermostat, water pump, etc. but would rather spend that money than 2 or 3k dollars on a new engine.

Edit: I should mention I am using a AEM CAI, and also running a TurboXS catback exhaust with stock cat/headers.

 

Wash the radiator and check the front tray, Then see how it does. The front tray will make a 15 deg differance on the temps.

If your temps stay high then I'd flush the cooling system. This is not the correct way, but to be cheap.

Disconnect the top radiator hose, then crank the engine and put a water hose into the radiator. Let it idle until you you have nice clean water coming out.

 

Next question:
Put the AP on something else that changes all the time, like MAF. Does it freeze up after a while?

It's possibly you only spiked to 216, and the AP locked up there. I had it freeze up like that a couple times.

No way your cooling system stayed stable at 216F for 2 hours of driving.

 

Good point. Mine does this far too often. In fact I've gotten in the habit of checking it when I see a steady coolant temp value for more than a few minutes.

Kind of a thread-jack but in the summer the Mazmart REmedy water pump and thermostat really work well to keep the temps down. I think, however, that in the winter they might be a bit much and I struggle to keep the car over 175f. I may have mentioned this to you when I was at your place, Mike.

If you're not financially able to totally revamp the cooling system, I suggest at least flushing the coolant and checking into all the insulating foam around the radiator. I replaced mine with some that I bought at Home Depot that's used for home doors/windows and immediately noticed a difference while at cruise speeds. Then again, most of the factory stuff was completely missing.

 

Thanks for all the replies. I will check out all these solutions and see if I can get any results. I will update you all sometime in the next few days.

 

I can back this up. I have no undertray (planning on getting one soon), and my highway temps are in the 200-Teens on 100F+ days. Eh, Texas. It's not exactly ideal, but it's been that way for almost a year on my stock 129K mile original engine, still get great mpg and power.

Just don't spank it when it gets that high. I slow down a bunch if it gets above 220, and if it ever got above 230 I'd pull over and stop.

 

Get that undertray. I was talking to a Mazda mechanic. He said that it was necessary on a Mazda 3 for proper cooling. He had no idea whether it was on a RX8. I suspect it is. And rotaries produce more heat than those 3's do. That tray likely creates a low pressure area in the engine bay that draws the air in from the front through the radiator.

 

You're right, it's needed.

 

Mine was gone for over 7 years then the ft worth heat cooked a coolest seal. I never had a clue. My high speed handeling suffered too the front end would get light over 125. I replaced it with some sheat metal from lowes a few months ago and saw a 15 deg differance that day.

If you still have the uprights. Then for 50 bucks you can build one from sheat metal shears and a rivit gun.

 

+ 1

 

Yeah, I know. I know, I'm talking to Scott @ RX8Performance about getting one pretty soon (hopefully shipped within the week). However, I don't have the side upright pieces, or any of the parts that mount to the front bumper, so it is a bit of a custom piece. Any day above 85F I always have my COBB watching the coolant.

Yes, high speed handling does go away quite a bit O_o I also need an alignment after some shock/spring install, so that doesn't help either lol.

 

Thanks everyone for the replies, turns out the AP was completely frozen up. I drove it around a bit today and it spiked up to 214 and stopped there so I switched over to my throttle position screen and sure enough it was stuck at 17% too. Unplugged and plugged back in the ap and temps were at 190 at a steady rate. Problem solved.

 

Still may want to consider a cooling system overhaul, since they shouldn't be getting that high. You are only a few degrees to go before you are hitting possible coolant seal failure range. Not really that much safety room.

 

It is definitely the next thing on my list, right behind an updated compression test. Thanks!

 

Because by doing so it will force the air thru the radiator.

Without the tray. Air will just go to the bottom of the car and not cooling anything

 

Did you inspect the under tray? Pull on it to make sure it's bolted up there good?

I still strongly recommend going wash her and getting the radiator good. 5 dollars at a car wash could save you thousands on an engine.

Then When you find the time spend 30 min to a hour flushing the system.

 

Glad it was a frozen AP.. I suggest an Ultra Gauge for day to day ops...

Also, check out the cooling mods in the $100 thread below.. Good ideas in there that help.

 

Sorry to steal the OP's thread but I've also been having an overheating issue that I believe might be related to the coolant but for some reason, I'm not allowed to make new threads. My issue is different, however, in that this morning while I was waiting in traffic, I noticed a white smoke coming from the sides of my hood. I looked at the temp gauge and it was halfway between normal and the red line. I pulled over to the side and let it cool off. I then opened the coolant reservoir and noticed it was empty. At the moment, I only had water, so I used that and made it to work. After work, I bought anti-freeze coolant and used it and all was fine. However, I used my car again for a quick drive to get food, and my temp gauge shot up again, white smoke was back, and when I checked reservoir, all coolant was gone. It seems to get better when I turn off my A/C and it tends to get hotter when I'm idling. Other threads I've searched suggest it might be the radiator fan, thermostat, or leaks of some kind. I have gotten the oil changed very recently-about two weeks ago. I'm hoping it's nothing too serious, as I don't think I can afford a heavy repair job right now. I'm hoping you guys could tell me what you think before I take it to the mechanic and he takes me to the cleaners. Thank you for your help.

 

I'm pretty sure you cooked one or more coolant seals. If the needle moves at all, it is entering deadly territory for our engines. The farther right it goes, the more sure you are to have killed the engine. Running out of coolant completely is a no-chance scenario.

Cooling system failures are REALLY deadly to our engines.

You can replace basically the entire cooling system for around $500 from Mazmart (new OEM radiator, coolant lines, thermostat, bottle, and cap), although at this point you need another engine too. You don't mention year or mileage, so you may or may not have warranty coverage on the engine from Mazda.

 

Anyone have links for the parts i would need for an overhaul? I will be getting a BHR radiator, and a high flow water pump with the lower set thermostat. But links to the other stuff i will need will be greatly appreciated.

 

RIWWP just told you the website and the parts you need in the post right above yours.

I'll get you started since you don't seem to be able to do it yourself. http://www.mazparts.com/en/rx8-cooling (see what this site has done to me! i'm being snippy!)

 

is it really that hard to search ?