Aw now what! II (Overheating)

[POS Racing]

Well the POS decided at the SCCA Test and Tune that it would heat up as I waited to make a run. It was at 3/4 on the gauge, I went ahead and made the run. (It is a POS after all.) It actually cooled off a touch, then when I got back to the pits it puked up a bit of antifreeze.. I called it a day since I still needed the car for the SCCA event on Sunday. Drove it home with the A/C and it never got past ½ on the gauge…… (A/C runs both fans )

When I got home I let it cool down and grabbed my enthusiast manual and started troubleshooting.

• *Checked the fan, it was tight with no bearing noises and spun smoothly.
  *Put a jumper on the fan and ground at the diagnostic port fan runs.
  *Measured the voltage to the fan it was 12V.
  *Checked the amperage on the fan it was in specifications. (5.5 to 7 amps IIRC)
  *Cycled the fan on an off about 100 times to make sure there wasn’t a bad spot in the fan motor it checked out good.
  *Checked the fan control switch located on the top of the thermostat housing it checked out OK.
  *Ran the car when it reached a set temperature it would cycle the fan on & off. I repeated this process sever times no problems.
  *Checked the fan relay as prescribed in the manual, it checked out good.
  *Drained the radiator; the insides look like new no buildups of anything, looked clean. The fluid was quite as green as the new stuff but still looked good.
  *Refilled the car with new antifreeze and then ran the car and had no issues.

So what was its issue that causes it to overheat? What have I missed?

Side note, made my 3 runs yesterday at SCCA, and had no problems car ran great, the gauge never moved past 1/2 all day…….

[chucka]

did you make it mad? it could be it just had the 24 hour flu?

[POS Racing]

did you make it mad? it could be it just had the 24 hour flu?

It's usually not that sensitive it has thick paint.

Figure I'll order up a new thermostat, and possibly the temp sensor (if its cheap)

[black roadster]

Original plastic radiator? If so, what color is it?

As Miata radiators age they turn brownish green. I's replace it with an all metal dual-core automatic tranny radiator from www.radiators.com.

Also, do you have a grill? Some grill can be too restrictive and cause overheating.

How many miles you got? If over 60k did you replace the waterpump when you did the timing belt?

[POS Racing]

Original plastic radiator? If so, what color is it?

As Miata radiators age they turn brownish green. I's replace it with an all metal dual-core automatic tranny radiator from www.radiators.com.

Original well maintained and clean radiator . Last owner & myself are all about regular maintenance, radiator has been serviced ever 30,00 miles since new. If I replace it I'm going to put a plastic one back in it since the OEM plastic is lighter than the metal one, which is important to us Cone Smackin’ Punks.

Also, do you have a grill? Some grill can be too restrictive and cause overheating.

Nothing in the front

How many miles you got? If over 60k did you replace the waterpump when you did the timing belt?

150,600 miles I need to review the old receipts, last one went in it at 120,000 miles IIRC.

I'd think if it were the water pump it would overheat while in motion and sitting still, not just sitting still. Isn't that a logical assumption

I do appreciate the info! :)

[black roadster]

I had overheating problems in my 10AE as you described. Dealer found nothing wrong. The waterpump failed at 19k miles.

[POS Racing]

Does anyone happen to know the P/N of the temp sensor that is located on the thermostat housing?? I'm not finding it in the Mazda parts book...

[black roadster]

You been to www.mazdaformance.com and looked at their PDF parts diagrams?

[POS Racing]

You been to www.mazdaformance.com and looked at their PDF parts diagrams?

Yeppers

[black roadster]

Call Marshal at Trussville then I guess.

[Flyin96M]

Mick,
What ratio of coolant to water did you have in the system? Was the fluid level low before you drained it? You could add a bottle of water wetter to the mix.

You can also upgrade the fan to the M2 style. I had to replace my cooling fan last summer and the new motor came with a new fan blade and wiring. It "seems" to pull more air.

You can also wire both fans to come on together. There is a write up on the pointy board where a guy just tied the trigger wires for the fans together and both fans torn on with out any problems.

So do you think the POS is trying to tell you something?

[POS Racing]

Mick,
What ratio of coolant to water did you have in the system? Was the fluid level low before you drained it? You could add a bottle of water wetter to the mix.

50 / 50 Wal-Mart Special Antifreeze! It's the same stuff I've always used with no problems in the past two years.

You can also upgrade the fan to the M2 style. I had to replace my cooling fan last summer and the new motor came with a new fan blade and wiring. It "seems" to pull more air.

Good Ideal, I'll look at my '02 and see the differences! Althought my fan seem to be within specs for amp draw and runs smooth. What happened to yours, what were the symptoms??

You can also wire both fans to come on together. There is a write up on the pointy board where a guy just tied the trigger wires for the fans together and both fans turn on with out any problems.

Yea I was looking at that this AM, but the sensor or relay may be intermittent, which still may mean no fans.

So do you think the POS is trying to tell you something?

Why yes I do, but I don't appreciate the language it's using!

[Flyin96M]

My symptoms were the same as your's it was fine as long as you were moving or the AC was on, but got hot just sitting. Mine went out shortly after I got my car back so it may have been left over from the accident.

As for the antifreeze you may want to make that a 30/70 mix with more water.

The fan upgrade was simple and it bolts up to the stock location. The new motor was larger and apeared more heavy duty. As for the blade it was the same blade but with opposite rotation for the new motor. You may want to see if you can either get one from a salvage yard or see if you can get a discount since you are a racer.

[POS Racing]

I still think it may have something to do with the temperature sensor that is located where the red line is drawn on '90-'93 cars. Later cars used the ECU to signal the fans but the early Miata used this sensor. All my tests indicate the fan is good, the relay checks out, so that leads me back to this sensor.

I will change the antifreeze ratio, I like that ideal!

[Adam Payrot]

Mick, that sensor is outrageously priced, something like $65 or so. I got one at Autozone for $20 but my temp gauge was erratic for a few weeks. I believe it was a grounding problem and not the actual sender itself.

[POS Racing]

Last night I pulled the sensor and cleaned it with some scotch bright, and put it back. It looked pretty good no nasty buildups or anything that could be deemed suspicious.

Then I sat in the garage for an hour with the car running, it would get up to temperature and the fan would come on run for a bit then shut off. In the hour I spent with the car the fans only came on 3 times, and the car never got hot.....

I think Adam may be onto something, I wonder if I might have been having a grounding issue with this sensor???? I drove it to work this morning with no problems and I caught every darn light on the way to work!