2006
55K
MT
Coolant in the radiator is full
Coolant in the reservoir is full
Engine temp is perfect

Once or twice a week for the last month the red coolant light shows itself. It's usually after some high RPM freeway stuff though nothing excessive whatsoever.

Stays on between 20 and 60 seconds then it's gone for days.

Ideas folks?

 

two possibilities:

1) system isn't actually full.
2) the sensor in the overflow tank is acting up. We've seen this with other cars and unfortunately the tank either needs to be replaced or you disconnect the sensor.

 

^+1 what jedi said.

He knows the way of the 8.

 

my car does the same thing. (2004 RX8 GT 6 sp.) has been for 3 yrs. Ive checked the fluid level numerous times, so for me, I am thinking its my sensor.

 

Do a search on coolant sensor or coolant bottle. You'll find it's a piece of junk and Mazda is on the 3rd part revision at least. Mine died at 33K miles and just before the warranty ran out. Dealer replaced it no questions. You can either replace the bottle, ignore the light, disable the sensor, or keep filling it (if that helps prob)...

Search is your friend.

 

How do you disable the sensor? Just pull the plug? Or do you have to provide some kind of dummy?

Ken

 

maybe clean the sensor?

 

Holy crap another one of these threads. I hate to scream search but this is like the the third thread on this topic in the last week.

 

Search peoples.

 

Haha! My light is on probably 50 percent of the time - started doing that maybe a year ago. Of course, I just did a quick search, then checked prices for the part, and learned to live with it. It's not like I can trust any of the stock dummy lights anyway. They are all on at one time or another I think (except the oil light - I don't think I could ignore that one if it was on).

 

Have to pull the plug and live with the light for now.....or get a new bottle.
When mine went out, I replaced the bottle and tore the old one apart. I was working on getting the range of resistance required to fake out the PCM so it would turn off the light, but I got side tracked and never go back to it. I guess I should go back and revisit my own thread and pick up on this again.

Not at you Ken, but to all the "new" posters........yeah, please do a search. Must be 20 or so related threads at the very least.

 

I remember your thread where you talked about doing that. It inspired me to take a shot at measuring the resistance. I got as far as pulling the plug off, but the holes in the bottle's connector were really small and I didn't have the patience to find some pins to stick in to get the meter on it.

One of these days. In the meantime, I've only had one false "on" from the thing.

Ken

 

From that thread, and this is where I kinda left off.

"If the switch is open(magnet float riding high indicating good coolant level and no light) and magnet falls with low coolant(closing the switch and illuminating the light), then why would unplugging the sensor cause the light to be on(it would be an open circuit)? Hmmmmm.........this kind of tells me that the PCM is looking for a given range of voltage on the return(not completely an open circuit.......ie....infinite ohms), but expects some range of resistance(say 10 ohms to ~2m or so)..................and will illuminate the light if outside that range, either low(magnet) or high(unplugged). Remember when I measure it without the magnet being there, I still read about 2m(if I remember right?)........and it was dropping. I don't remember where it stabilized cause I didn't care, as long as it didn't drop all the way to 10 ohms and it didn't.
So knowing this info, it should therefore be possible to find the right value resistor and just plug it in to where you disconnect the sensor and you'd have no light. You would however have to check your level and not depend on that light ever coming on. I'll see if sometime in the coming days I can figure out what that value should be, but anywhere greater than 10 ohms and below ~2m might do the trick".

I need to re-verify the above and perhaps I can get to it this weekend!

Dave

 

A sensor was my guess as well. I'll see what my dealer says. Meanwhile, the CEL came on last night. Thanks folks.

 

Manual, 2004, RX-8, 66K Miles. I have noticed a couple of web sites that sell this part. Not sure if it's the same one or not. If I where to replace the sensor itself then would I need to pull the whole coolant resivoure out?

http://www2.partstrain.com/store/?Nt...ant+sensor&N=0

 

Yes Dave, and remember I said that the Sensor Stalk actually bends slightly with age, getting hot and then cold a thousand times, then the little round magnet gets stuck and gives a false reading...

Look Mazda (I think most car makers), have had issues with these for the past 25 years...they are toys basically.

You see the Wiper/Headlight Washer Bottle also has a level sensor and we have not heard of issues it is similar in design to the coolant bottle one, But the huge difference is the plastic does not get as hot, nor does the fluid...so no problems.

 

BTW, Dave inside the Tube is a "Read Switch" which it's circuit is either Open Or Shut, for memory this circuit is NC (Normally Closed), so when the magnet moves too far the reed switch opens and presto a dash light, I really do not know how you can fool the PCM as the signal works via the reed swith...ON or OFF, there is NO in between.

 

If the reed switch is normally closed, then wouldn't you just have to put a jumper across the plug? Maybe the resistance range Dave was finding was due to closed and open for this switch not being purely 0 or infinity, and the PCM (rather than a simple relay) being in the act.

Ken

 

Yep, I'll have to recheck everything this afternoon or tomorrow, but as strange as it may sound, I think it's a NO(normally open). As I explained in my thread after taking the bottle apart, the sliding the magnet DOWN to where the reed switch in the tube was.......closed the switch. Sliding it UP and away from the switch caused it to open, but it didn't go totally wide open.
Here's the link again with pics!
Ash.................like I said, I'll go and recheck everything I did, but I think I'm right.


https://www.rx8club.com/series-i-trouble-shooting-95/coolant-bottle-greatest-secrets-revealed-182793/

 

Dave,
Yes the reed switch is Open without the Magnet Ring, but Closes when magnet is near, so because the magnet is part of the switch it is classed as NC.

Your pic shows it open because there is no magnet there..the magnet ring is technically part of the switch...which is Normally Closed.

When the magnet moves or gets stuck it is opening (reed switch) the circuit...you get a dash light.

This type of reed switch has 2 parts to the switch, the magnet and the twin bi metal strips, like Window and Door Reed switches in House Alarms.