I searched but i didnt find what im looking for. My question is this: I have an 88 s4 vert and all the cooling system is in excellent condition and i run 50/50 water coolant. For the most part with the a/c on in the 100 degree heat in texas my factory guage reads in the middle. Every once in a while in traffic when ive got the a/c going it gets just a hair higher but never over that. Would yall consider that normal with the a/c and this 100 degree heat? It probably doesnt make much difference but my cars black too. I was thinking of trying some waterwetter but i just wanted to check. I dont have any leaks and nothing is out of the norm. Its all factory except for the radiator and it has the metal top and bottom instead of plastic. I know the factory guage isnt necessarily accurate but i just wanted some reassurance. Its hot as heck here right now and i want to make sure she is ok. All of my hoses and everything as far as maintanance is concerned is up to date. thanks everyone, Karson

 

sounds about right. but you may want to run more like 65/35 heavy on water like mazda recommends for summer weather. If you can get a hold of some water wetter or the equivelant that wouldnt hurt either.

 

I have the same question. My 88 SE runs just under the 1/2 mark usually. This is with a recently installed Mazda oem thermostat and 50/50 coolant mix. I always thought S4's were supposed to run at about the 1/4 mark...

 

Mine pretty much always runs at 1/4, maybe a tad higher if im beating on it or its really hot out. I would probably get worried if it reached 1/2.

 

Its been said that the oem temp sending unit is not accurate. This is not true, they are very accurate. I have a buddy w/a v8 in his 7 and he uses all the factory sending units to run the stock gauges, he also has set of gauges in the engine bay to make sure the factory is reliable. On my 5speed car, the temp was always just below 1/2. On my auto car it was just a little higher, even with a trans cooler. I believe the temp where the thermostat is wide open, is somewhere around 200deg.

 

The S5 temperature gauge is pretty much worthless. It's been sterilized to the "Cold, Warm, You boiled your coolant off 5 minutes ago" version of a gauge.

The S4 gauge is fairly accurate. IIRC, "hot" is somewhere around 95C - hot, but not exactly failure point.

As for my gauge (88 SE):
Cooler weather driving, it runs about 1/4.
Hot weather (90+), it runs about 1/3.
Hot weather with the A/C on, it runs just under 1/2 on the highway, slightly higher in town.
Hot weather autocrossing in 1st gear with a lot of time spent on the rev limiter, it got to about 2/3rds. I was starting to get uncomfortable with it there, but it's good for a while longer.

-=Russ=-

 

its pretty hot here lately too, i just flushed my radiator out and changed the thermostat. now its at about 1/4 to 1/3 at night when its about 80. during the day with the ac off its at about 1/3 and with it on its a little below 1/2

 

I don't know why people insist on running 50/50 coolant mixtures in warmer-than-Arctic climates. Mazda says 65/35 will protect you down to 3degF. Extra coolant does nothing but lower the heat transfer capacity of the water/coolant mixture. Yes, it makes cooling WORSE! Only use as much coolant as is needed to protect the engine from corrosion and the water from freezing.

 

1/4 way up is good, 1/2 way up is bad, above halfway up shut it off immediately. You will more than likely blow a coolant seal due to overheating if you drive with it much over 1/2, I did.

 

so 65% water and 35% coolant? if it works, i can flush it out on thursday i suppose. my coolant temps are increased a bit due to summer weather. looks like i should read up on the fsm more. always more to learn.

Ryan Shannon.

 

Yep. What I do it buy a 4L container of coolant and empty it into a 20L container, then fill the empty container with water and dump that in, then do that once more. That gives me 12L of 2:1 water/coolant mix (66.7% water, 33% coolant), enough to fill the system and do top-ups later.

 

mine always runs at the 1/6-1/4 mark and i live in PHX AZ wich is like hell.

 

The only reason mine was 50-50 was because thats how the original owner had it. I changed that yesterday though. I put 20% coolant and the rest distilled water with a bottle of water wetter and it made no difference on the guage. If half way is bad then what should i do to try to get it cooler? All the stuff like the undertray and all the pieces are still there. The radiator is new as are the hoses and as far as i know the thermostat. My fan works correctly too. Is there a colder thermostat i can run? Id be willing to do that if thats what it takes, Last sunday with the heat index it was 115 here so i dont blame the car for running so warm. I just dont want to harm something.

Edit: Id like to add that i dont know what kind of thermostat the car has, ive only had it a couple months. Should i just opt for a new mazda thermostat and see what that does?

 

Is there a difference between the S4 and S5 thermostats? Maybe the dealer sold me the wrong one? I guess ill try the diluting my coolant mixure, and see if that helps with the hot temps

 

Whats that in celcius?

 

Absolutely! An unknown thermostat is a good place to start cooling troubleshooting.

3degF = -16degC.

 

yea i noticed that too i live in cali and i jsut took mine out for 10 minutes or so in 80 degree weather and it went half way up the gauge.. i turned on heater and that took it down to 1/4.. any suggestions?

 

Well Im in TX also and my 88 vert runs 1/4 till noon when it gets hot out and then it runs at 3/8. When sitting in traffic with the air on it gets up to just below 1/2. In DFW we sit in traffic alot. God its wonderful here!

 

My hats off to ya for the traffic up there. Its gotten pretty bad here but nothing like what you get to put up with. Mine does exactly what yours does and ive got the a/c on. So im wondering if i should even be concerned cuz it never goes past what i mentioned earlier. Its just when i hear coolant seals going bad and all it scares me. I dont want to ruin the motor because of our weather down here.

 

Well, there's only so much you can do.

If you're worried about heat, get an OEM Mazda thermostat, flush your cooling system and run the 65/35 water/coolant mixture that the FSM recommends. Also (if you don't have it), install the stock under-belly tray. If all this isn't solving your cooling needs, consider upgrading to an aftermarket radiatior like a Koyo or a Fluidyne.