Nameless

Happens during long drives both city and highway driving. It's never overheated, but it's above the horizontal point on the temp gauge and it jumps up and down. On a cold day and with a short trip it wont climb above the horizontal point.
I have a M2 CAI, M2 DP, and Apex'i N1 Dual. Have a PFC waiting to install. But what else could I do to this baby to keep it cool? It's high milage 100k.
Radiator, lower thermostat, new water pump, pulleys? What do you guys think? Thanks in advance

juliof

Get a temp guage I have a digital one there great you will see fans turn on at 230F way to hot no wonder these cars over heat. Install the 207F miata thermoswitch or any adjustable fan controller best thing is to have fans turn on under 210F. Replace the thermostat you could still have the original one in there, get a larger rad I have the SR ultimate they were $600 when I bought mine I think they are on sale for around $400 this is the biggest rad for the FD.Also make sure both fans are running right, flush cooling system well and seal around the rad after you install a new one.

David Hu$tlerhoff

it seems that this Evans coolant would help as well

weaklink

what is evan's coolant

weaklink

ok i read about it on their site but I don't understand. How do you convert to low pressure or no pressure setup? change the cap? what happens if you run it in your 7 with the stock cap on?

Nathan Kwok

My recommendation is not to worry about Evans coolant for now, because to even run Evans you'll need a cooling system in tip-top shape. A clogged and marginal cooling system may have big problems with Evans because it has a higher viscosity than regular coolant. I used to have a hot running car and I got a Fluidyne radiator and a new thermostat, which completely solved my problem. I also got a temp gauge. Its most likely your thermostat not opening all the way, so you can try just fixing that and seeing what happens. I used to run slightly above horizontal (~220F, dangerously high) on hot days and the problem got worse so that I would be paranoid and turn on the heater full blast all the time. Now my temps never budge from ~180F when the car is moving, are very slow to rise at idle, and when the fans come on at low speed (btw this is ~195 with driving lights on, ~207 w/o driving lights on), the temps just drop like a rock back to 180. FWIW, the big thing about Evans isn't that it is a better thermal conductor, but that it is totally inert, meaning you never have to change the coolant (or maybe every 10 years, you get the idea), and it has a very very high boiling point, so you never have to worry about water pump cativation, can run low pressure, etc etc.

Nameless

Thanks, that's exactly what I wanted to hear. As soon as I get some money I'll have to do that. Wanna help me with installation Nathan?

juliof

Where do you have youre temp sender installed? those temps are way too low. Stock fans turn on low at 230F with sender at thermostat housing, even turning on lights turn on is only 225F-228F.You might have a thermostat that is stuck open, or a bad temp guage or youre fans are allways running too keep temps at 180F in traffic.

Nathan Kwok

Juliof,
You are partially correct, my mistake. The fans come on at low speed at 221F and medium speed at 226F (http://www.scuderiaciriani.com/rx7/fan_circuit.html). According to my gauge, the fans come on at low speed just before 200F with the driving lights on, but there is no documentation regarding this "glitch" that only appears on '93 models. Without the driving lights, I didn't recall it getting quite up to 221F before low speed, but I don't spend a lot of time idling around and it takes quite awhile to get that high. Plus, I always turn on the driving lights if I'm idling for a long time. In any case, my gauge may be reading a little low. However, seeing 180F when moving is perfectly consistent with the operation of the factory thermostat, which begins opening at 177F-182F (see E3 in shop manual). Although it is not fully open until 203, apparently the partial open condition is enough to adequately cool the car, or maybe my particular thermostat opens more than usual at the initial open temperature. The sender was installed in the water pump housing just ahead of the thermostat FWIW. I should test the gauge one day by idling it until the fans come on at low speed without the driving lights to see exactly where they turn on. They aren't stuck on btw, I know that for sure.