Ok I need your guys' help. I have an overheating problem that I'm having trouble diagnosing. At idle the car is fine, the temps are nominal.... around 84 celcius (I have a power fc to watch the temps). Even in downtown crappy traffic my temps aren't bad. But as soon as I get on the highway or put any load on the engine (cruizing at 3000, accelerating up to highway speed shifting around 3000) the temps start to rise (to the point where I have to pull over and cool down).

I've replaced the thermostat with one out of a 20b (opens at 65celcius) to try and lower the temps. It worked for idle temps, but it still rises otherwise. I've bled the system to eliminate the air factor and I'm pulling my water pump tomorrow, but there are no visible leaks so I'm not sure whats up. Also I have a black magic fan thats wired to the ignition for the mean time, so it's always on and I added a double groove pully system for the waterpump/altern.

Any ideas?

 

That tstat opens too low. Order an oem replacement from Mazda. It is a 180 deg fahrenheit tstat. 65c = 149fahr

 

well if it over heats on the freeway but not in traffic then its an airflow issue is it not?

I have read that some e-fans dont pull enough cfm to cool it under load, and that the fan can actually restrict air at freeway speeds, making it worse.

I have a ford 3.8L v6 efan and it was doing ok till i put on a fmic and gps kit. I made some ducting and cut out my bumper some and it fixed it. before the ducts freeway temps were 210+... now they stay about 195.
I set my efan to come on at 200... so the only time it comes on is while stopped at a light.


something to think about.. maybe that fan is not gonna cut it this summer.

 

Two things scream out there:

1. The wrong thermostat (and a lower setting thermostat does not increase cooling capability- don't understand why people think it does)
2. Black Magic Fan

So put the right thermostat in there, and confirm that the black magic fan is wired for the correct pulling direction (could be wired backwards and have exactly what you are describing- either way at highway speeds the fan should not be even on)

And then make sure that the engine undercover is in place.

 

Stock rad Im assuming?

Koyo will help immensly.

Also as mentioned:
1) Belly pan in place and intact
2) Use the correct thermostat
3) E-Fan(s)[possibly go dual] with a proper shroud

 

^^ Icemark: are there any pictures which display the engine undercover? I know I am missing mine and want to make another one from a sheet of aluminum or something.

SleeperFC: My car was doing exactly as the poster described and it ended up being a faulty tstat for me. I would overheat if I was on the freeway or going up hills, but everything else was fine.

 

Ok you all mentioned thermostat. I understand that I need the proper stat in there...but having the colder one should not cause overheating problems. So right now my concern is still the overheating. My fan is wired the proper way. I don't though, have the undertray, aswell there is a fmic.
My question is would the undertray help that much? I mean, I know it helps but could it stop the temps from rising even when the fan is on at all times? And having the fan on on the highway, could it then restrict flow? Or would it increase it by sucking more air through?

 

if the fan does not freewheel at higher air flows, it will be a hinderance. If it does not freewheel, it will not suck any more air in than it could at any other time.

If the fan is on at highway speeds it is not wired correctly.

And you need the undercover for proper flow through the oil cooler and radiator- in other words the two things that cool down the motor.