searched everywhere but cant find anyone with the exact same question i have..my 09 rx8 is fine but i'm trying to help my cousin fix his 04 rx8 gt 6 speed..long story short his car runs hot like its building up air in the coolant lines i suspect because you can pull off the cap and the car cools right back down..you can top off the coolant and drive fine for 15 minutes or so and then the car will try to overheat again..i am really new to the rotary scene and so is he..BUT we just installed new water pump,new thermostat,checked to make sure both fans work,checked the oil and have never seen it to be milky(not sure if this happens on a rotary) and the heat and ac still work even when its starting to run hotter than normal..can anyone shed some light on this subject? thanks a lot!

btw its a 2004 gt 6 speed with 110k miles and only around 40k on the new engine that was replaced before he got the car..thank!

 

How do you know it's overheated?
He got aftermarket gauges? What's the reading on it?

 

no its stock gauges..actually he's cheap lol..the stock gauges messed up and he put atx gauges in it lol..but it was overheating before the gauge cluster swap..and its getting anywhere from 2/3 to almost into the redline sometimes..he claims he's never let it redline

 

Since the gauge was mess up, how could he know....besides the oem is a dummy gauge, by the time it moves, you've blown the engine...

I doubt it's overheated, just a mess up gauge....get a proper gauge and go from there...

 

Technically, if the needle on the OEM water temp gauge starts moving from it's normal place, it's already overheating, in critical territory, and engine damage is imminent. The gauge doesn't start moving till it's too late usually, and a single event can warp the housings enough to let coolant into the housings, and then it's pretty much game over. Best you can do is nurse the engine until the coolant leak completely destroys the sealing ability of seals.


Your post seems to confirm this, by suggesting that you have to top off frequently.

 

depending on how many times you have topped it off, and how much, you may just be burping the air out of the cooling system. with a COLD engine, disconnect the line on the top of the throttle body, if nothing comes out, start slowly filling the coolant bottle. pay attention to the height of the line, and the full mark on the coolant bottle, you cannot make water go up hill.

If you can get significantly more water in, that might help. If not, I was wrong.

Also, under the $100 thread in my signature are several things that could help. Good luck.

 

i have a feeling he installed the thermostats wrong, or the thermostat he got is wrong.

 

i put in the thermostat for him and installed it just like the oem one was installed and it was just some oem replacement that he bought..the car just will run hot after 15 minutes or so once you top it off..dont see any coolant leaks and no smoking or water in the oil(like i said i dont know if this happens with a rotary) the car will run perfect and then it starts moving off of half way and slightly rises and it will actually fluctuate up and down slightly but quickly..you can pop the cap off and it will blow off lots of steam and the car will cool right back down..it blows out so much steam that the overflow hose off of the reservoir sounds like a horn blowing its so loud and vibarating so much and blowing out so much air

 

You may have a leak into the cooling system in the compression part of the housings

You will usually see bubbles in the coolant when you rev the engine with the cap off

 

i will get him to check this..i will probably try to get him to meet me to work on it soon again

 

oem replacment? u better be sure it has the pin on it because most oem replacements do NOT have it, and it will cause problems. and telll me u didnt get the stance one.

 

he said it was the beck arnley one he ordered..from autozone or something if i had to guess

 

Sounds like I've got the same issue with my 04 High Power, so I'll just hijack this threat if that's alright.
I realize the magnetic float looses boyancy, so that's probably why the warning light comes on after maybe 5 minutes of driving, but why are my after market gauges showing temperatures up towards water boiling (100 C) after about 15 minutes easy driving if the coolant isn't actually running hot?
I've topped off the coolant and oil and I can't find any leaks anywhere. The gauges haven't been showing high temperatures (at least not nearly as quickly) until recently either, so I'm pretty sure they're alright. So what's with the overheating all of a sudden? Is my radiator/coolant system clogged somehow?

 

Stock Tune will turn the fan to highspeed ONLY if the coolant has reach and above 101 Celsius. so it's not supsrised to see coolant temp at 100. when I had stock tune I see it all the time.

and the only way to tell is to have it test. Are you located around NYC? maybe I can help.

 

Get the OEM one, or Mazmart Lower temp thermostat.

 

I live in Norway, so not really close to NYC no..Thanks for the offer though!

The water temp rarely ever passes 100 Celsius, at least not by much, so what you're saying about the fan on highspeed makes sense. However, it doesn't explain why the temperature rises so quickly unless the fan only works on high and doesn't turn at all before the coolant reaches 101C. Is that even possible?
Also, how do I go about testing it at the different settings and whatnot?

 

^ that's how my stock set up worked too. No fans till 101*c. Fans would turn back off at 95*c.
Installed a aftermarket fan kit and now my fans turn on at 87*c and back off at 82*c.

 

faulty coolant temp sensor?

 

What fan kit do you have??

 

MindsEyeEngineering Fan kit. But I must warn you, the seller is actually "Mazsport" and according to these forums he is a scammer or was a scammer. I didn't know about all the drama till long after the purchase. So take that as you want. Honestly now that I know how the fans work I would just wire in a switch myself to turn them on when I want... Not that the kit is bad or anything, It's been working fine for about a year now. Highest recorded temp since install is 201*f (93.8*c), that's with a/c on in heavy stop-n-go traffic, summer time heat. And I'm running 30/70 (Coolant/Water) with a bottle of Redline's waterwetter.

http://www.ebay.com/itm/Mazda-RX-8-C...item3a74b64e78

-Shawn

 

^ So about that switch, is that something that's easy enough for for a noob with basic tools to do without making things worse?
The reason I'm asking is because I'm trying to sell my car without spending too much more money on it first. Overheating isn't really a good sales pitch.. (not to mention that I have a P0410 from the busted air pump, but that's a different thread)

 

Click on the "$100" in my sig. Step 13 is an easy fans on low mod you can complete with a little soldering iron. There are also several other cooling related tweaks as well. Everything can be done for under $100 total.

 

^Wouldnt it better to wire them up to turn on high speed instead of low speed?

 

^Low seemed to do the trick for me. High was noisy. I now have an MM Cobb and the fans come on earlier. I only use the wire for track days, still on low. If you wire for high, you have to do both relays.

There is actually a chance that high actually makes things worse at slow speeds by moving so much air through the radiator that it cannot easily escape. It just goes out the bottom of the engine compartment in all directions, that includes the wheel wells, the oil coolers and out the front to get sucked back in as well as leaking back around to the front of the radiator where it is useless for cooling. Some of the other cooling mods in that thread involve blocking off those passages with foam to keep hot air on the hot side.

Not sure if it will help here, but it could be a contributor.

 

I understand what you mean about the fans being noisy on high.

Now about that second paragraph, and I know this is a little off topic so sorry op, what are your thoughts on increasing ventilation through the fender vents? This car's engine bay seems to be noticeably hotter than other cars I've owned (Never measured). It appears there is no where for hot air to escape at the top part of the engine bay. There are small hole in the inner fender near the Master cylinder and washer fluid, shouldn't opening up those holes some help with moving hot air out the top of the engine bay and away from the radiator?

-Shawn