Hey, interesting thing was going on with my Rx8 while driving on the highway. While I was driving I realized that if I was driving faster than 72mph, my engine would start to overheat. If i kept it below 72mph, e.g. 70mph cruise control, it would not overheat.

So while driving, I started focusing more on the revs and it seems like when I go over 4k, the engine would start to overheat. If it was below, everything seemed ok.

Checked the coolant level and it seems to be OK but would need to recheck it since I was not able to check it when it was entirely cold.

Anyway, you guys have any idea why this occured? Planning to bring the car in to the dealer this week.

2004 RX8 6speed w/ 75k miles

Thanks in advance

 

how is your oil?

 

Just topped it off about 3 weeks ago

 

when was it last changed? Do you check it every other few fill-ups?
Check for leaks in the coolant lines

 

Actually I am up for an oil change pretty soon and do not check it too often but can always recheck it.

I will try and see if I can see any leaks tomorrow.

 

you do know that this car drinks lots of oil? Make sure that every other fill-up with gas, you take 2 minutes to check your oil level. Keep a quart of oil in your car at all times. Also, how often (miles) do you change your oil?

May be a reason why you're over heating...

 

What gear are you driving that fast in?
Water pump cavitation?

 

1. How did you monitor your engine temperature?
2. Does your car starts showing sign of overheating if u let it idle for a long time?
3. As you accelerate into the 4k rpm zone, are u easing into it or full throttle?

 

I am aware that the car does drink alot of oil. On average, I add oil every 2k miles. I change the oil every 5k miles.

I am driving in 6th gear. Since I was doing highway driving I was just trying to set the cruise control.

1. Monitor using the stock engine temp gauge
2. No signs of overheating while in idle
3. Easing into the 4k rpm zone.

 

Hrmm... if its the stock engine temp gauge thats moving around, then you would have some big problems as thats basically a dummy gauge that only moves when its "too late". Could it be a tripped up thermostat?

 

Uhm... how do you know it was overheating?

 

Its funny that i found this thread. When my car was stock, it did this also, jsut when setting the cruise on a summer day at around 75mph the dash light would come on. Throw the car in neutral and coast for about five seconds and the light would go off and all would be fine for another ten minutes... then the light would go on again and so forth.

 

Agreed that the stock "gauge" won't indicate any problem until it's quite severe. Invest $50 or so in an OBDII reader so you can look at the real engine water temp. Overheating at cruise is a bad, bad sign: avoid driving it, get fixed quick.

 

If you're absolutely stuck, I've found that if your overheating, pull over, crank the heat on full for a few min and get back in until you get to a shop!

 

So drove around town the last two days and had no issues like I have seen on the highway. The gauge stayed normal with no issues. I did not try to repeat the high way driving again.

Eithercase, I will be bringing it into the shop to see what they say.

Basically, the gauge is just fluctuating.

This is interesting that you state this because I have had this happen a couple of times to me and I used the same exact procedure. Except my light did not continuousy come on and off. It pretty much just stayed off after occuring once.

As for everyone else thanks for the advice so far.

 

aftermarket water temp gauge FTW!

 

The stock gauge has 3 zone despite being a dummy, zero to halfway is normal, halfway to about 2/3 is telling u its starting to overheat, 2/3 to Hot means get a new engine.

 

+1

my aftermarket gauge showed the temps much higher than normal while cruising. checked the oil, flushed the rad, replaced the thermostat and water pump...turns out my fuel pump was going south at 40k.

after the mm fuel pump, temps went back to normal.

 

How much oil is missing when you add it every 2k miles? That seems like a lot of time to wait to me, most people check oil every 500 miles or so and have to sometimes add a bit. You really don't want to just let it go down really far and then refill...

Your checking your oil every 2k miles, I CHANGE mine every 3k lol.

 

Check to be sure your lower radiator hose is not collapsing at higher engine RPMs. You can do this simply by holding the engine revs at 4,000+ and watching the hose behavior.

 

Why would it do this and how would one fix it if it were happening? Curious if this is a common problem or what the issue would be.

 

It is not common, is only a remote possibility, and happens when radiator hoses get old and spongy.

 

Ok, this is still quite the issue with my car. I was out yesterday adjusting the tune to get it best i can untill i can get a pro tune. I was out for about 45 minutes, doing everything thing from partial throttle acceleration in any gear to full throttle runs through the gears. Everthing was fine and i had to issues. This was because i would do my partial throttle or full throttle run then pull over and make the changes. Sometimes i would drive five or six mintues plau with partial throttle in differnt gears seeing what the car was diong. Coolant light NEVER came on throughout any of this.

Well, i am done for the day, and am about 10MI from home. Start drivign normally home and WHAM within two minutes of cruising at arond 4000k the coolant lite comes on. I check the laptop and it says the Water temp is 84 Degrees. Now, Throughout the day, i have seen this temp on the laptop before and never had the light come on.

I put it in neutral and the light went off after the RPMs dropped and i am talkign about seconds after i hit neutral. Then i played with the rpm a little. It Will never overheat from 3750 or les RPM no matte how long i hold it there or whatever i am doing. Only when i hold it at 4000 rpm or above will it overheat.

To Recap:

Will not overheat at IDLE
Will not overheat in in town stop and go driving.
Will not over heat if under 3750RPM for long amoutns of time
Water temp was 84C when coolant lite was coming on
Stock temp gague never moves
Only needs 2 seconds in neutral to make the light go off
If the light comes on and i am at 4000 RPM and i keep the car in gear and lower RPM to say 3000RPM the light STAYS on. Will only go off if its in neutral.

Also entire cooling system on the car is stock, except the coolant overflow has been relocated.(obviously was not relocated when the car was doing the same thing when stock) At first i thought it may be the extra heat by adding a water cooled turbo, but then i remember it did this when the car was stock also, HOWEVER it is doing it quite a bit more now. Lets say every 5-10 minutes as compared to not every trip and once ever 30 min when stock.

I have not gotten to check the Rad. hose yet Charles. Still waiting on a second body to give me some help with that.

Any other ideas?

 

Do you mean the red "greek temple" looking light when you say the coolant light?

 

correct the greek temple light...