I bought my '88 na last sept and the temp was always less than halfway when fully warmed up never crept up. Now that it's summer and hot outside the temp just goes up, especially on the highway. It's hot today so I had to drive at 100km/h with the heater on full blast to keep the temp down and I was hung over, not fun lol. Anyways, I think it's the rad is just old and can't cool well enough anymore, but do you think it's possible it could be the thermostat. Also for a replacement rad is it worth it to buy a koyo or just get a generic NAPA rad.

 

I purchased a Koyo unit after a small leak came from my stocker, I noticed a cooler temp thoughout the last few months.. I also added a mix of waterwetter and a little 50/50 blend coolant instead of straight coolant.

But if it really is your rad that is the problem then a factory replacement will suffice. I still wanted more though.

 

Overheating usually tends to lead to a bad thermostat or radiator cap(which is commonly overlooked) If the cap does not seal right the pressure in the cooling system will not be correct and will just dump coolant into the overflow(is the overflow full all the time?) you could also have a bad vacuum from the radiator fill locatoin to the overflow.Thermostat is usually number one cause so check that first(heck replace it ! its cheap enough!) if this information doesnt help you could be looking at a new radiator depending on how much the inside of the endtanks and radiator are eroded.when you flush your coolant is it extremely discolored?(kind of auburn or rust looking deposits inside fluid?)If thats the case you need a good flush or new radiator,or both.

 

the overflow doesn't fill at all, the fluid looks just like new. The temp only really creeps up when it's hot especially on the highway, just seems like the rad can't dissapate the heat when it's hot outside. Also when looking at the rad it looks like it's the origonal, I'll try the thermostat first because it cheap but I think it's the rad.

 

i got the same car, like today i drove out to cedar point and my temps stayed about halfway point

 

If it is the original OEM radiator, it's probably clogged. I have owned several FCs over the years. If it is running cool, the guage should be at 25-30% of the "sweep". When the car was running in the 40-45% range, it turned out the radiator was clogged. The coolant may look fine, but the passages were shot. I recommend getting a Koyo unit (just be sure to save the brackets from your stock unit...you will need them). Put in either Redline's Water Wetter or Royal Purple's Purple Ice and distilled water. Since you are in Toronto, use some antifreeze if you don't plan on changing your coolant before winter hits. While you are at it, make sure you replace the t-stat, pressure cap and hoses if you are not sure as to their history. Oil may be the life blood of the rotary, but the coolant system is very important, too. Good luck

 

Remember: S4 temp gauge shows 25-30% when operating temperature, S5 shows 50% on the gauge.

 

Alot of GOOD info on this thread!..Only other thing I would do is to replace the Rad cap with an OEM cap.If your cap is not functioning.it will make the temp go Up Too.no way to get the expanding Coolant out.so it will make the engine hotter.(my thinkin anyhow)..I'm no expert ,But I have never had a Car overheat on me Yet!.I replace the Thermostat and Cap,along with a Good Coolant,as soon as the car is mine.No problems.Good luck to ya GScully.