DR_Knight

iTrader: (23)

Alright, so the car I'm describing is a 1988 GTU. So it's N/A, stock motor, all cooling stuff is stock.

Alright, so before people start going off, "oh, there's other threads about this, y dont you try searching". I have. I've researched into this on the forums for a bit now.

I have always wondered why s4's show the normal operating temperature on the stock temperature gauge at a little above "C". After just installing a full sweep electric temperature gauge, I was amazed to see that the thermostat is opening and regulating the temperature at 160 degrees F.


My problem may be: I installed a temperature gauge, cut the upper radiator hose, so I can install a sender on a little connecting piece. Of course, it only shows the temperature of the coolant after it has left the thermostat, but it should show the temperature that the thermostat is regulating. I'm not the first owner, and it is possible a 160F thermostat was used, but I highly doubt that after seeing how many people have this problem.

My friend has a S5 Turbo motor as a swap. My friend placed the sender in front of the thermostat, which shows the temperature of the coolant before it leaves the thermostat. He's showing 180-190F which I see as normal while looking at other s5's.

My question is, Why do S4's use a 160F thermostat? Most cars use 190F in order to become more efficient. Is it because the design of the rotary engine is different from piston engines, that a rotary is more efficient at 160F? I believe S5's operate at 190F, or Mazda just adjusted the temperature gauge. I've been hearing people criticize others, stating "oh, you must have put in a 160F thermostat", but after hearing this over and over again, it has to be a manufacture design. Will it be any more efficient while operating with a 190F thermostat? I passed smog no problem, so that means the engine is still quite efficient. Could this be a possible reason why I see s4 engines last longer than s5's? Do engine builders see sludge buildup in s4 motors because of the lower temperature?


I've read about people buying thermostats from Mazda, and they're specified to open at 180-190F. But, then they go home and test them, and they open at 160F?


Edit: I've just looked on the technical data for a 1988 rx7. Both turbo and N/A thermostats are said to open at 177-183F.
Any help would be greatly appreciated. If my thermostat is faulty, along with all of these other S4 owners, I guess I'll be asking Mazda for another thermostat, and if it opens at about 155-160F, I'll bring it up on this thread.

chaz9999

Good question. I've always wondered if seeing such a low reading on my stock gauge ('88 SE) meant there was something wrong. My operating temp is usually a little above the C, but I've never tried a digital to see the actual readout.

Also, does anyone have a numbers reading for the stock gauge?

Aaron Cake

iTrader: (1)

The stock thermostat is supposed to open at 82 degrees C. Note that a thermostat is not a switch. It will begin to open before that temperature.

In order to get an accurate temperature measurement you must measure BEFORE the thermostat. If the engine is under low load it's not making much heat, so the thermostat is not wide open and thus only a little warm coolant flows into the upper hose. This mixes with the cooler coolant already there and makes the temperature seem lower.

Mazda has started to sometimes substitute thermostats as of late. It's going to cause a lot of annoyances.

The temperature should be stamped on the thermostat.

The S4 gauge is supposed to be at 1/3 or so and it's a REAL gauge. The S5 gauge has three positions: cold, normal and "new engine". It's not really accurate.

HAILERS

I bought three or more thermostats from a place out in califoria (wish I could pronounce Caleyfouria like Arnold), Signal Hill place, and they all turned out to be 160* thermostats. Not good. I saw no degree number stamped on them. I know the temp I was seeing was right because I got the temp off RTEK2.0 which in turn reads the temp off the water thermo switch on the back of the water pump housing..

Go buy a thermostat with the degrees stamped on the thermostat and 180*type.

DR_Knight

iTrader: (23)

that's a good point, so I'm guessing that when the engine reaches normal operating temperature, the temperature gauge means 180F when it's a 1/3 of the way on the normal portion?

I'll try running my car a little hard, but nothing crazy. Wouldn't the coolant eventually reach some sort of equilibrium? As where the coolant in the block is the same temperature as the coolant in the upper radiator hose (that's where i placed my sender)? But I guess since the coolant's still not getting hot enough, the thermostat will not open all the way.

It's good advice though, and I still want to look into this further. Probably by testing my thermostat, or get a new one. I mean, never hurts to replace 20 year old parts.

DR_Knight

iTrader: (23)

and would you happen to be talking about mazdatrix? or is it another place? just to know where not to buy thermostats from.

HAILERS

MAZDATRIX