ok first off i have a 91 NA FC. its all stock with original parts. and today the coolant level sensor crapped out on me(at least i think thats the problem). i drove to work and all was well. i get off work and drive 1 block and the damn annoying buzzer and add coolant light pop on. i pull over and turn the car off immediately. the car didn't even get to its standard heat level yet but i stop and wait anyway. i check the coolant level and its full. overflow tank was at full and it was full at the gooseneck with the rad cap. it looks like there was a leak from the coolant level sensor in the past but it isn't leaking at all anymore from anywhere from what i can tell. i see no pools of any type of fluid whatsoever anywhere.

anyway i read a bunch of threads on this and i was thinking i should just ground out the sensor and install a mechanical temp gauge (since apparently the stock gauge sucks from what i've read), and just monitor the temp through the gauge as you would on any other car and continue to check the coolant level as i normally do before every drive.

any help or suggestions would be greatly appreciated. i have a want to buy thread looking for a sensor and a rad already and i'm scouring the classifieds hourly. i've called my local mazda dealer and they wanted 100 bucks for the sensor and it needed to be special ordered. it seemed way overpriced to me so they will be my last resort

 

Hey BOB!
on a S5 the stock gauge really isn't all that accurate..you got Running temp then "wtf,new engine".
Now,if you want a aftermarket gauge you can tap the waterpump housing and install one there (search that please) or try a In hose adapter like the ones that BuddyClub or HKS sell.,(you split the upper rad hose and install a pipe that has a threaded portion for a temp sender).

Honestly I would not get rid of the coolant level sender as it is an Alarm that tells you when your coolant is low.If the Temp sensor gives out then at least the level sensor will be there to let you know if something is up.
I run Mine on my Koyo on the Hopped up S5TII I have and I thank God for it.

If the sensor is Buzzing and is damaged,you can temporarily ground the wire from the harness to the Frame of the car..BUT remember that you will now have NO way of telling the coolant level.

..and IF you REALLY get stuck I will send you one..(but as I said,try your WTB thread first as I am in CanoeCountry!)

 

Just ground out the rad level annoyance and get a nice simple VDO gauge and sending unit.
Why would you want the hassle of a mechanical unit instead of electric?

And why is it necessary to check coolant before every drive?

 

i was reading something that about mechanical gauges vs electric and twisted it around in my head and wrote that lol i meant electric. i don't want liquid all over the dash if a line busts. anyhow as far as the coolant checking goes. its just something i do no reason except me being ocd about it

i found this gauge on summit. its electrical it seems decent
http://www.summitracing.com/parts/atm-3337

as for tapping into the water pump housing i don't feel that comfortable enough in my ability to do it myself, and since it seems like thats the optimal area i will have to find someone to do it for me. for now ill just get the replacement coolant sensor and do a full coolant and air flush and fill her up with brand new coolant.

 

Just put the gauge sensor where the original went, no need to tap the housing.

 

That gauge should be fine. Here is the one I have. http://www.summitracing.com/parts/atm-4337/overview/

Also you can get the coolant level sensor at Autozone now. Sensor - Radiator Coolant Level | 1988 Mazda RX7 1.3L FI Rotary | AutoZone.com
You just have to order the one for the an '88 car and swap the plug. The sensor is the same only the plug is different. Mazdatrix only sells the '86-88 one cause the '89-92 one is so exspensive for just a different plug.

 

I'd try a little more diagnosis on the level sensor and check for leaks.

Make sure the wire to the sensor isn't broken and the connection at the plug is nice and clean and not corroded.

Check for leaks anywhere again, including hoses. You may have coolant at the neck near the thermostat, but may have air at the top of the rad. There's a bleeder plug near where the rad hose enters the rad at the top. Open the bleed a little and let a little coolant out (a few shots worth) as you add at the cap near the thermostat.

 

I was quoted 70 for a new sensor from Mazda, and even then that was way high. I know its a shameless plug but I made a write up a while back on how to repair the sensor since I didn't want to spent stupid money.
https://www.rx7club.com/2nd-generati...r-diy-1054321/

I was informed after the fact that auto zone also caries new aftermarket sensors for around $20.

As for the gauge, its not to hard to tap the tap neck to place the sender. A drill, center punch and a npt tap and your golden.

Good luck with finding a radiator!

 

Two things:

- If you're installing a standalone temp gauge, you DO NOT NEED TO DRILL/TAP ANYTHING.
Just replace the original sending unit with your new one.

- I consider the water level nag to be completely superfluous and not worth spending a penny on.
The point of the cooling system is to unload heat from the engine and as long as your shiny new temp gauge says the engine is happy, who cares what the coolant level is? It's obviously enough or you'd be overheating.

 

Just for clarification on the sending unit. Aren't the threads different? That being said I thought I saw on another thread that there is an adapter for them thus you can just replace the stock one like you said.

As to the coolant level sensor not all cars even have one so I agree. Not a big deal to ditch it.

 

The stock sending unit is 1/8 x 28 British-something pipe thread, the standard aftermarket unit is 1/8 x 27.
Since it's a tapered fitting, it will jamb on the taper before the thread mismatch really matters.
I've done it several times with no problems.

 

I like the coolant level sensor/nag, since it's extra insurance if you don't regularly check the temp. And it'll tell you something's up a little earlier (if due to coolant loss).

 

yeah that was my thinking exactly. i mean i've had cars that didn't have any of those type of sensors only a temp gauge and they were fine without the sensors.

i thought and read the same thing about the different threads

yeah im gonna flush the whole thing and look for any leaks in the process. i didn't see anywhere to fill by the thermostat. im also gonna ditch the plastic oem thermostat cover and replace it with an aluminum one i have

i felt the same when styx was talking about it but as i said before, lots of cars don't even have it so i figure i can live with out it especially with the ritual of checking the coolant that i do LOL

 

The Series 4 cars had a cap on the thermostat cover. Your Series 5 does not.

 

yeah i read up on that. how can i go about bleeding the air out of the rad. ive read about it here but it seems everyone has S4's and the rads are a bit different

 

I believe both s4 and s5 rads have a little phillps head plug next to where the upper hose goes in.

Or you can jack the car up, leave the cap off and let it run, that burps the system also

 

i know of the screw on the bottom but what was puzzling me is that i didn't see the screw on the upper rad hose. ill have to check again thanks

 

ok so i grounded out the sensor and now i'm paranoid. i let the car heat up to operating temp after grounding it out and the gauge never past the middle as it normally does. no more buzzer or idiot light, but no more safety net as you guys were saying. i ordered the autozone replacement and it shall be here by thursday. ill be getting the temp guage immediately, but i will be flushing the coolant soon and refill it with mazda fl22 coolant. is it possible the rad got clogged somehow?? i mean i don't think it could have clogged or sucked in air by sitting through 1 measly 4 hour work shift could it??? thanks for all the help guys i totally appreciate it. if need arises i will be asking for some more help. i usually consult my FSM and haynes manual or read some threads here but they weren't any help this time.

 

Not very likely, but if you really want to know, rent/borrow/etc. an infrared gun or thermometer to check for hot or cold spots on the rad.

Also, get the coolant system pressure tested to find any leaks. If it holds pressure, then it was probably some air at the top of the rad that caused the sensor to go off. I don't even think you need a new sensor...probably just some air, especially since you're not sure how to bleed the system (no offense, just being honest).

But getting a good quality, reliable gauge is a good move anyway, ignoring all the rest.

 

Here is my refill method. Others may be different. I haven't had any air issues that I'm aware of.
1. Fill with coolant.
2. I used to then squeeze the lower hose but now I have a spring in there so I do the top. Bottom worked better though. This burp the air out of the rad. so to speak.
3. Coolant level should go down. Top off and repeat. If you get too much and squeezing will overflow I just put my hand over it to seal it. The excess goes to the overflow. Do this till it won't take anymore.
4. Start the car and leave the cap off( I actually start it with the cap on but remove it before it builds pressure). Coolant usually goes down. Add coolant repeat previous procedure.
5. Once it seems to not take much stop and wait for the thermostat to open. Be ready when it does as the level starts rising and will come out the filler neck fast. When it starts rising quickly put the cap on.
6. Go drive a mile or two. Not far take some coolant with you. Just in case( I've never needed it). Usually the low level buzzer will go on and off after a bit as the air gets to the top of the rad.
7. Go home let the car cool enough so you can take the cap off without getting sprayed. Top off the rad. and fill the overflow to the full line. You're done for now.
8. After a couple of days recheck the level and top it off and the overflow if necessary. Now your done.

 

hey no offense taken. i'm not born with this type of knowledge so i gotta learn it from somewhere

thanks for the procedure. will definitely be doing it today or tomorrow

 

After filling and letting the air out the bleeder, I squeeze the rad hose too. Also let the engine warm up with the cap off until the thermostat opens. I skip some of the other steps and don't worry about coolant overflowing off the cap neck. Then turn the engine off, add until filler neck is full, then add cap.

Couple tips. As always, make sure you have a good rad cap that holds the proper pressure, and vents when under negative pressure (to let coolant back into the rad from the overflow when the engine cools. Also make sure the overflow hose has no leaks or bad connections at the rad/thermostat and bottle. Or else you'll loose coolant (when engine warms), and will suck in air (when engine cools).

 

thanks for the tips. i've discovered that my top rad hose is a bit bloated so i will be replacing the hoses right away before i get the gauge. do you think that could be the culprit?

heres what i concocted to ground the sensor out so i didnt have to splice the original connections.





from the last pic you can see the green on the lip of the rad but there is no leak coming from anywhere. i looks like there was a leak coming from the sensor but it isn't leaking anymore from what i can tell. ill be replacing the little o ring for the sensor anyhow for safe measure. i work maintenance at a movie theatre and deal with a bit of plumbing. from my experience its most likely a stupid little 4 cent gasket or o ring that screws the hole thing up LOL

 

ALL SEEMS TO BE WELL. it seems it was just the sensor. i swapped it out and no buzzer or light. ran the car up to operating temp and all was fine. i bought new hoses as mine are bloated and i bought a new OEM T Stat from forum vendor JAuto. i figured id just swap the t stat for a fresh one seeing as the car still has the original one from 91 still in there.

 

How can you tell that was the original, factory installed t-stat?