chocolate_supra

My wife's FD made its first trip to Sevenstock this weekend, and we noticed some odd things happening with our cooling. I've read everything I can find on the subject and I understand how the stock gauge is center-heavy, but luckily the previous owner installed an Autometer temp gauge and a Fluidyne radiator. So, on to the goofiness.

While driving along on the freeway on a hot summer day, the Autometer will tend to read around 210F or so. If driving for an extended period of time (or stop-go driving in town), it'll get up to 220-230. The odd thing is that the stock gauge would not even reach center at this point. Around the time the Autometer reads 200-220 or so the stock gauge's needle would rest around the C, although not bottomed out on the peg.

Since the stock needle never really got to center I figured the car was always running pretty cool (since we have the Fluidyne), even if that meant "cool" for a rotary was 225F. After talking with some people, however, I now know a little better. Everyone I spoke to at Sevenstock runs around 190-200 on the freeway and didn't even come close to 230 climbing the Grapevine, where my Autometer gauge was above 240 (it was at this point I saw the stock temp gauge FINALLY read center). This means I'm running around 20-30 degrees HOTTER than the people with STOCK radiators.

So now I'm not sure what to think. I know the stock gauge is center-heavy, but I've never heard of it reading consistently low! I figured that if an electronic gauge dies, it DIES, rather than reading consistently lower than average. Is this something the factory gauge tends to do when it goes bad? This concerns me because if the stock gauge is operating properly that means I'm not running warm enough, whereas if the Autometer gauge is operating properly that means I'm running way too hot! I am thus confused, and would like to know if this is a problem anyone else has had. I would very much like to find a happy medium.

Sgtblue

iTrader: (16)

Forget the stock gauge. Ignore it.
Assuming your Autometer is accurate, you are running too hot. Many believe that 240 F. is where the coolant seals begin to stress. Some things to consider......

*Your radiator fans. Make sure they are coming on when they should and you have all speeds. Search for more info.
*Flush and replace coolant. Use as much distilled water to coolant as you can comfortably get away with for your climate. Be careful to properly "burp" the system to get the air out and add some coolant/water to the overflow bottle using the "dip-stick".
*Assuming it hasn't been done, replace your stock thermosensor with a series 5 FC thermosensor. It will kick fans on at 95 C instead of the stock 108 C. and tend to keep the engine cooler.
*Make sure the radiator is clean of debris. Especially between the condensor.
*Replace the t-stat (use OEM). It's inexpensive and easy to do. And if you do it when you replace the coolant you won't even make a mess.
*Stuff a little upholstery foam in any gaps you have around the radiator. Any place where air would be allowed to go around instead of thru the radiator face.
*Make sure your under-tray/belly-pan is in place and secured properly.
*Check the fins of your oil cooler(s). Clean and straighten as needed and make sure ducting is in place for them as well.

arghx

iTrader: (3)

autometer water temp gauge

unreliable piece of ****. I've seen some crazy readings from an autometer.

Sgtblue

iTrader: (16)

Yeah, but the stock gauge DID move to center. Not good and I suspect he's running hot. .

chocolate_supra

So the stock gauge isn't supposed to move to the center on the FD? I thought it was supposed to move to center after about 160F?

Anyway, the radiator was just recently flushed and burped by a professional rotary mechanic, radiator fans were tested to come on at the proper speeds at the proper temps (as per what the Autometer read), there's no debris and the undertray and ducting are good.. so I guess I'll be looking at a thermostat!

Sgtblue

iTrader: (16)

No, it shouldn't move to the middle. The stock gauge is not linear. It goes up to just below the mid-way mark for any engine temperature between bathtub "warm" and normal operating temp. But if it moves even a millimeter beyond that, your car is probably overheating. It really is worse than if they had not put a gauge in at all. That's why I told you to ignore it.
Take it back the mechanic. I agree with the others at 7stock. Something is going on.
Just out of curiosity, where is the sensor for that aftermarket gauge?

chocolate_supra

The sensor was put into the thermostat housing, as far as I can tell. I see an aftermarket sending unit and wire coming out of it, and when warming up the Autometer stays at zero before suddenly pulling up to around 160, which I've read is what happens when you place the sensor there.

Ernesto13B

iTrader: (4)

I hate to argue, but I believe the stock gauge should read "the middle" during normal operating temps, I know mine does. My after market water temp gauge reads 180F usually at highway speeds. The only time my stock gauge reads below the middle is when the car is still warming up. Maby we are talking about 2 different things, idk. At sevenstock I was very pleased at how my car performed. The hottest it got to, was 210F, and then the FC Thermoswitch kicked in, and temps dropped quickly back to 180-190 on the grapevine.

Yea 240F is pretty darn hot, I'd just recommend all of the things mentioned above. When I finished my vacuum hose job a few months ago, I noticed my coolant temps would continue to rise and they got to about 230F, where I was too scared to let it go any higher so I turned the car off. Later after bleeding the air from the coolant AGAIN several times, I never had this problem again. I just refused to believe it was that simple, or at least that was my solution.

I found a thread on this problem a while back I think it was Dale Clark? Anyway, this is a common problem when installing the temp sensor into the thermostat housing. I would think temp's would be inaccurate in that location for the reason you just mentioned, but that's just me. I installed mine in the throttle body coolant hose where my gauge will show coolant temps starting from 0 Degrees

Check out this thread https://www.rx7club.com/3rd-generation-specific-1993-2002-16/big-fat-fd3s-cooling-thread-571088/

Sgtblue

iTrader: (16)

Then maybe MAZDA didn't even get the stock gauge calibrated uniformly. But mine stays at about 8:00 o'clock...maybe 8:30 and has (fortunately) NEVER shown higher regardless of what is indicated on the PFC commander or my temp gauge.

Ernesto13B

iTrader: (4)

Wow I didn't know that. I thought all the FD oem temp gauges would be the same? Interesting. The one time I did get my water temps to 230F I turned the car of ASAP and when I did the OEM water temp gauge was still showing the middle. After I had the car off for a few minutes, my stock gauge finally after a huge delay showed slightly above the middle, but the aftermarket gauge was still showing 230F, temps had not increased at all.

The oem water temp gauge IS very flawed and any temp readings shown, are readings 20-30 seconds ago and are not current. I'd recommend moving the aftermarket water temp gauge to the throttle body hose to get a more accurate reading. BTW chocolate_supra nice FD, and nice to see you at SevenStock! Hope you get the issue resolved so you can make it next time

chocolate_supra

So new thermostat and move water temp sensor location. Sounds like I have a to-do list! Hopefully I won't have anything to do past these. I did notice that if I clutched and coasted down the hills at speed on the grapevine and got the air running through the radiator, my temp would almost immediately drop from way too high to down under 200F, so I'm hoping any issues with the radiator or airflow can be ruled out and that the issue is simply not having the proper flow through the engine. I hear these thermostats are prone to failure anyway, and who knows if the previous owner even put an OEM thermostat in it?

Ernesto, I hope y'all had enough fun at the bbq without my ranting and Kat's revving. Already looking forward to next year, by which time we should be running with efini turbo power (and the proper engine temps)!