A different thought, maybe dumb, but different.

From other posts, the stock water pump cavitates at high RPM. Maybe more with older coolant, I have no idea. Water Wetter some have also said caused foaming at high RPM. What are the chances that the coolant is foaming coming out of the pump, the foam is getting into the bottle, and the foam cannot support the weight of the float. Might explain the high RPM issue. I only see it at high RPM.

Have the people who changed the bottle taken that opportunity to change the coolant as well, giving fresh coolant, that is less likely to foam?

Or, does all of this sound like crap?

I think it sounds like interesting crap. :)

Mark..........If you wanna come sit in the engine bay, I'll run it up to redline in 3rd and you can see if there is any foam in there? :)
I think you might be able to hang on long enough to get a look.......might be hot though!



I'm just kidding.
I guess anything is possible.
I put in a new bottle and destroyed the old one for this thread.
I did do a coolant flush/change when I put the new one in, so who knows?????

Dave, at RX-8 Production Start...April 2003, the Coolant Bottle was an 'E'.
Yes, the latest is now 'M'...and possibly the last.

:)

YOUR PM???

Yes sir........I know. Did I write something that lead one to believe I didn't know?
I must go back and re-read..........especially since I'm not aware I might have mis-spoken????

I edit my post above that said "The new revision is "M"" to read "The latest revision is "M'" maybe that was it?

The problem been, if the light doesn't come on when they turn the key into the on position, they'll look to see why not. I presume it comes on with the rest of the warning lights in that position. Must check. I've heard stories of cars failing before they even hit the ramp, on airbag lights.
Welcome to the nanny state.

HUH....do you Really believe they are going to look for a Coolant Warning Light??, at Ignition ON, after all it is NOT a Safety Issue like Air Bags, beside NOT every car has the same warning lights/sensors.

WHY do you not "try" the suggestion first, that is unplug, Ignition, Start.

I can assure you it will not flash once started, as far as On when Ignition is ON, you can check that one.

The low coolant light has started to come on at odd times,but always with high rpm and 7000rpm to clear carbon.Reading here seems to be the sensor.The question is,any danger to the engine if you coolant level is normal and can you go to higher rpm with the light on.Thanks

No problem. It's just a bad sensor, does nothing except put the light on.

Mine comes on at random times, mostly when just cruising along, not necessarily at high rpm. If a passenger sees it, I've got a couple of stories I tell them, depending on whether they think it looks like a Rolls Royce radiator shell or like a Greek temple.

Ken

^...........think most of us would agree with Ken.
As long as you have proper coolant level and mixture, it shouldn't be any issue what-so-ever.

It usually starts out just coming on at high rpm's and slowly gets worse where it will stay on more and more frequently, even at lower rpm's.

My Coolant Bottle OEM Overflow TUBE MOD.
 

Thought I would add this to Dave's excellent thread...:)

My own Overflow TUBE Mod..with a Genuine Mazda Coolant Bottle Hose from the FD RX-7.

It is well documented that the "original" RX-8 overflow tube has its limitations, that being it is small short and known to direct Coolant down and around Power Steering cabling and plugs...NOT GOOD.

Now some guys have simply bought a length of tubing from Autozone or wherever and connected to Coolant Bottle overflow and re-directed it.

I decided on another option...

With this Genuine Mazda Part you get a stronger black overflow tube of around 12 inches long in total, but, the ends are heat molded with the original 90 degree bend and another longer 90 degree bend at the other end of this RX-7 tube...so it looks like a long U shaped hose.

What to do....

Connect the smaller looking 90 degree end to Coolant Bottle OUTLET, bring the tube around to the front left of Coolant Bottle and rest between your painted Radiator Support Panel, then around the Air Conditioner High Pressure Switch and then position the larger end of black Tube OUTLET DOWN so it is located just in front of the Headlight Seal area, there is a gap and the top corner of Radiator can be seen..

So basically the Tube or Coolant Bottle Overflow is now positioned top far left of radiator as you look at it (Passenger Side L.H.Drive)...So if it does overflow coolant should not get anywhere near the Power Steering Wiring.

Just to add, you do not need to push this new tube through any holes, it just sits snugly on the top between your Coolant Bottle and Painted Radiator Support Panel.

What I also did (OPTIONAL Mod) was to place a very small plastic catch bottle (about one or two fluid ounces in size, that is all that will fit) and the new black outlet tube/hose sitting inside of this small plastic catch bottle, so basically any minor discharge from my Coolant Bottle is caught...Frankly, if you are spewing more than an ounce or two of Coolant out of Bottle you have other issues that need looking at.

So, How does it look...VERY Neat and original looking..
So, How does it work...so far no problems, I was not expecting any.

Where to buy the RX-7 molded factory OEM Coolant Hose??, from a Mazda Dealer.;)
Montgomery's, vendor here is just under $7.00.

Or Paul from Mazmart will get it in for you.

Don't delay your purchase as stocks are limited before a price increase.

Part Number..
N3A1-15-383 Hose - SU Made in Japan

https://www.rx8club.com/attachment.p...1&d=1292978565

I have the latest Mazda EPC (December 2010), and the M Coolant Bottle revision is still the latest used in production and IMO the last...there has been no change since May 19,2009.

Thanks! Good to know!

I also like your overflow hose mod, but as you might be aware, I had some blue hose left over from my catch can install, so I used that and provides a better match for me. I had enough left to run it down beside the fan all the way down to one of the holes in the undertray.

Recently I'm experiencing the coolant light issue too.
Here's what happened:

About a month ago it came on the first time around 4k rpm, figured it's low, so I filled it up (just around F mark) with regular coolant. And it never come back.

I did my coolant flush few weeks agot and replaced my coolant with 20/80 coolant and distilled water plus water wetter. And I also over filled the F mark, but not all the way to the top of the bottle. Since then, my coolant light comes up from time to time, usually after highway spirit, around 4 or 5k rpm. It goes away about a min or so, did NOT lower the rpm.

One time I poped the hood right after I parked the car and saw coolant/water boiling inside bottle. Some came out of the overflow hose too.
Has anyone experienced this?

Would overflow cause the light to come on?

Thanks in advance

Overflow wouldn't cause the light to come on IMO, but shouldn't overfill and better extend that overflow tube so it doesn't get on the power steering connectors!
Keep and eye on it, you may have other issues like a bad thermostat. I'll have to see if mine boils in the bottle, but I know I have popped the hood and looked right after a good drive and not seen it. You have any way of checking your actual temps?

No, I don't have water or oil senders....but planning to get them in the future tho. I'll extend the tube for now, i guess.

My other guess is that, cuz' it's overfilled, while in high rpm/temp (boil?), it disturbed the magnetic ring and trigger the reed. Just a guess...

I'll definitely keep my eyes on it...

Quick update, after I leveled the coolant down to full mark. The light hasn't come on so far.
I'll keep my eyes on it in the next few days and see how it goes.

If my theory is correct then that means light go on simply because the heat pressure from the coolant created enough turbulence to bounce the magnetic up and down to trigger the reed. Maybe that's why the top of the bottle is a distance away from the F mark? To keep certain amount of pressure/heat which also stabilized the magnetic ring.

Then that'll explain why light come on when coolant is low or overfilled.

We'll see...

It's good data, but we pretty much know that the float lost buoyancy over time in the old bottles. You may however have caught another interesting phenomenon in your case.

I had to run back and forth to the airport in Orlando yesterday cruising around 82mph for a round trip of 125 miles and as soon as I got home, I popped the hood and no boiling. My water temp never did get above 200F the entire run over and back though.

Ok, so it came on again...and this time after I parked the car and poped the hood, there are smoke coming out, which smells like coolant and the coolant are below the F mark in the bottle. Which leads me to overheat issue rather than simple sensor issue...

I'll do more search on it for now....

Yep...........I was afraid of that............good luck!
You have any puddles under the car? Hoses look okay?
Have any in the exhaust? (Worst case scenario)
Here's hoping it's just the thermostat!

Fill it back up with car off and cool. Pop the hood and wipe all the hoses down, then start her up and let it get to normal temp. Shut it off and see if you can tell where steam(coolant) is coming from. Of course be careful though, it will get mighty hot and don't let the car overheat. A lot of times it can be difficult to see a leak with car running, but once you shut it off, it will show up!
Oh................look around your cap too, some have reported cracks in the lip of the bottle where the cap goes on.

No, nothing under the car that i notice, but I'll double check.
And nothing in the exhaust, thx god. lol

I'm sure the steam is coming from the coolant that came out of the overflow hose, because there is a small puddle at the cooling fan "cleavage". lol
I'm looking into cooling fan and thermostat at the moment...something is just not functional....

Ma car needs to be cool! lol

Yeah, make sure both of your fans will free turn.............spin them with car off and see if they spin freely.
Then you need to see if they are coming on when they should.

Any parts that could cause cooling system not functional?
I don't have any CEL, just radiator light from time to time, so i'm guessing it might not be thermostat, but I don't know...

How about water pump? How can I tell if it's functional or not?
I'm no mechanic in anyway, I would appreciate any suggestion at this point, and look into those.
Thanks in advance...

Found this...

In addition...

/\ Sorry to come into this late, BUT, did you bleed out AIR in your cooling system originally??..

By now though it should have worked its way out with a few drive cycles of hot and cold, would have seen your coolant bottle level get lower?..

Just a thought I would throw that in there???..