I just suddenly developed this problem earlier today..
I'm driving normally, all is fine until I reach a red light. Then I sit there and watch in fear as my temp. gauge rises quickly near the red line, so in a panic I shut off the car.. but the light turned green, so I re-started and kept going and all was fine.. it went down as I drove. So when I got to my parking lot.. I parked it idling (just like it'd be like at a red light) and sure enough I watch the temp gauge go up..
so I pop the hood and touch the radiator, its hot, but not out of the ordinary..
the clutch fan appears to be engaging and disengaging.. from looking at the engine and driving, everything seems normal.. so then I wonder if its just a bum gauge. (stock).... but then I wonder why it dosent go up while i'm driving.. because the air is cooling the radiator.. so it must be a true cooling problem...??

I don't understand how my fast idle can still be engaged (semi-warm start) and the temp gauge can shoot to red line within a few seconds.. when the radiator is clearly not even hot.. dosent the fast idle sensor, or the choke sensor sit near the water pump?

Does this make sense to anyone?
I hope so.. I'm planning to take the rx to the city tomorrow and dont want it to die!

P.S I already checked the coolant and oil levels and they are full

 

When was the last time you replaced the thermostat? Make sure you use an OEM mazda one from the dealer.

 

thermostat sticking? or maybe just a bubble in the coolant line...

if its not smoking, then it probably isnt something to really freak out about or lose sleep over.

crappy coolant, water pump slipping, bad fan clutch...

 

that happened to me only worse so i got a used 13b radiator and had it flushed but yeah make sure you get oem thermo

 

Thats what I thought it was too... I replaced the thermo just now and took her for a drive.. everything was perfect.. stayed at 1/4 or under

but when I got home i idled in the driveway for a few more mins and the gauge started fluctuating again...
I'm hoping its just air pockets from my thermo install

 

Just because the fan engages, doesn't mean its not slipping. In the manuals, there is an explanation on how to propery test the fan clutch.

 

Do a forum search to see the good results people get from using the Lisle funnel. Simple and effective way to eliminate air pockets. Google search to buy one.

Also check your fan clutch, since that tends to cause problems at stops. It should feel like there's taffy in it when you try to turn your fan by hand. But I believe a fan clutch fails slowly, not all at once.

 

Is there a better way to test the fan clutch than using the fancy tool the manual says?

I keep thinking to myself.. its not possible for the temperature to go up 80 degrees in a matter of seconds at idle.. thats crazyness

 

Sounds like a fan problem. If it stays fine while your moving but goes up that quickly while your still, I would think its a fan issue. See while you moving air is going through the radiator and the oil cooler as well. Also remember that the oil does a lot of the cooling for these engines. Make sure the oil cooler is working. I think you have the beehive right? Look on the forum for beehive issues. Mines a FMOC so its a different animal. Remember its not just coolant that cools your rotary, its the oil as well. Thinking of that, make sure your oil filter is good too.

 

Oil and filter has been replaced in the spring.. only about 4,000 kms on it.. i do have a FMOC, oil and brand new coolant levels are fine..
I guess it must be the fan, though I still think its the gauge.. do people get bad gauges?

 

I started it up again to diagnose some more.. and the gauge shot up over the red line.. 120 celcius +

so i shut down the engine.. and i felt around.. theres nothing near that temperature... the engine was hardly warm

 

sender/gauge... though i dont know how to troubleshoot a sender... other than to buy another one... lol

 

not trying to go of topic or high jack the thread but I am having a problem with my clutch fan it comes on sometimes when ever I start the cr but then when ever it gets up to temp while driving it never comes back on wtf.

 

okay.. I just replaced the clutch fan.. same problem..
Within 2 minutes of a cold start the temp was above half.. is that even physically possible?

The gauge has to be wrong..... sender.. ?

 

make sure that the wire is not grounding it self out that goes to the sender unit and all the conections are good I had the same problem started the car ran for about 2 mionutes and got all the way past the red wigledthe wires around and it worked fine ever since.

 

wheres the sender? is it the one at the bottom of the rad? or at the water pump

 

Just for safety sake, I'd recommend installing a mechanical temp gauge and forgetting about the factory POS. I bought an iequus triple gauge cluster (volts, water temp, and oil pressure) from bumper to bumper last year and it was ~$50.
https://www.rx7club.com/showthread.p...ghlight=gauges

 

I actually already have that triple set.. in my new center console i'm building not installed..


BTW. Thanks a million rotarycrazy.. that WAS THE PROBLEM
I had just installed a new driver side heater core hose, and i had bumped my sensor wire into the oil filter tower causing it to ground and give false reading.. a simple piece of electrical tape solved this big headache

 

Never mind I see you fixed it. Cool.

 

glad that worked for you.