Miata Cooling Design Question/Issue

Just picked up a 97 NA8 with 135K on the clock. I thoroughly test drove the car and saw everything was in order. Previous owner had replaced all major hoses and the fans. Radiator had no "burnt" look. Coolant was nice and green and clean. But when I started doing AutoX-ish maneuvers for about 5 minutes in a parking lot, the temperature gauge started to rise and get close to the H. I stopped, turned heat on, and let the car idle and it returned to normal. No problem.

I've read our radiators have horrible design. I know many buy the aftermarket Koyorad's or switch to some crazy duty 37mm or 39 mm or even 55mm all aluminum radiators. But everything I read says that is only needed for miata's with forced induction and track duty.

I figured I'd just drain my radiator and refill with distilled water. Did so, burped system of air, all good and gauge stays at 11 o clock. moved to 1 o clock after some vigorous parking lot maneuvers but obviously much better than before.

So the question is, with my power output being stock, and increased cooling of my watered down cooling system, do I need to really worry about doing AutoX in this damned insane Tx Heat? Obviously I'll watch the gauge but I'd rather just drive more and worry less.

Also, I typically run the car with the AC on, so that both fans are on, helping out cooling I believe.

Do I need to do anything else to the stock cooling system? Or should I upgrade since this is my nominal street car with an emphasis on heavy future AutoX and Track Use?

The radiators in these cars (and any modern car) are not a lifetime part. If you don't know the service history a new radiator may not be a bad plan.

My 2002 with 106,000 miles that I bought new is on now on its second radiator it was under $150.00 for a replacement OEM style radiator. I have tracked it and AX'd it for years.

Thing is when the radiator fails your odds of spending serious $$$ to fix your baked motor increases exponentially.

It's actually like 80$ off amazon for a TYC. (even more reason to replace, right?! Ha)
I know these are to be replaced, but like I said, the system looks so new. And the coolant is also brand new. No reason to believe the seller lied when he said he went through it all, based on my thorough checks. I was thinking a thermostat replacement wouldn't hurt either.

If I have issues this next Saturday, both parts will be yanked and replaced.

Any other cooling tips?

The fluid may be new now but what was in it just before it was changed? Just changing the coolant does not normally get all the old crap out of the coolant system, but it does make the coolant look new. ;)

The key part of the cooling system for removing the heat from the engine is the radiator. So if the car is getting hot I tend to question the condition of the radiator. Seems logical to me but what do I know.

No no, you make sense. I haven't had a repeat since I first got it and I drive hard, so maybe that's why I'm nonchalant. But I was thinking the radiator is next on the list.

I feel that the designers did not anticipate the miata being thrown around in 95 degree heat, 2nd gear, with not alot of speed and air flow through the radiator. So that's why I was curious if the OEM system is up. For the job. Which it seems to be.

So another question. If the needle is creeping towards H, I should stop, but leave the car idling and so keep the water pump working, but if it hits H, I should turn it off, correct?

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Originally Posted by Yamahaman444

So another question. If the needle is creeping towards H, I should stop, but leave the car idling and so keep the water pump working, but if it hits H, I should turn it off, correct?

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The more air you can force in the nose the better IMHO. But yea if your headed towards H I'd stop.

You have the under-tray and all the aerodynamic do-dads that Mazda bolted on these cars back in Hiroshima??

No undertray. I read it helps with airflow especially at lower speeds, correct?

It helps at all speeds

Well dang. All I gave left from Japan is those super sweet shipping anchors.

1. Get an under tray $65 + shipping - don't drive the car without one! - (anybody have the link for the Rosenthals replacement?)
2. Get a new thermostat $7 - I use a 180o Super Stant from NAPA - http://blog.miataracer.com/2014/01/s...pec-miata.html
3. Get a new radiator cap $12 - a Stant from NAPA works.
4. Replace your coolant with:
a. $10? - a 20% coolant (anti-freeze), 80% distilled water - coolant (anti-freeze) protects from freezing and corrosion but doesn't cool well. Water cools better! 50/50 mix will overheat for AutoX/Track.
b. $10? - or distilled water and RedLine Water Wetter (not Purple Ice), you'll need to either keep the car in a garage from Oct to March or put some anti-freeze in for winter. Purple Ice will not protect from corrosion with distilled water, ask me how I know.

If these don't work think about:
1. The water pump. How old is the timing belt? There maybe a date on it. If it looks old, change it, the water pump, cam seals, front seals, idler pulleys and valve cover gasket. Gates makes good replacements. Trackdog has a kit.
2. A new aluminum radiator - either a stock one or a CSF. It is big, not too expensive and available at either 949 Racing or Goodwin - http://949racing.com/CSF-radiator-miata.aspx

If you really want to spend some money unnecessarily, you can install a re-route: http://www.miataturbo.net/race-prep-...-thread-79930/

Pressure test it…...If its not holding pressure, you can throw fancy parts at it all you want.
OEM parts are fine for a stock NA Miata, plenty of them running with no issues.
I use 33% coolant (1 gal of real coolant and 2 gal distilled water)
I also replace the cap with a uprated lever cap.

Eric, Rosenthal doesn't exist anymore…..Tommy's at Priority Mazda now.

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Originally Posted by Rogue

OEM parts are fine for a stock NA Miata, plenty of them running with no issues.

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+1

I drive mine very hard on the track and AX and have no issues with my OEM setup.

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Originally Posted by Rogue

OEM parts are fine for a stock NA Miata, plenty of them running with no issues.

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Originally Posted by jrj512

+1

I drive mine very hard on the track and AX and have no issues with my OEM setup.

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+1

+2...and I've run for weeks, autocross included (gasp!) without a belly pan.

I had read about the 50/50 not cutting it and since I drained and refilled the radiator with distilled water, I have not had an issue.

I just wanted someone to chime in and confirm that OEM can handle this ridiculous heat

At least I didn't start an oil thread ;):clap:

^If you go all distilled, don't forget to add some antifreeze before winter.

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Originally Posted by Yamahaman444

At least I didn't start an oil thread ;):clap:

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Or worse, oil filters.

Wait. Synthetic or Dino? Hahahahahahaha

I didn't realize replacement bellypans were only $65 Ive been running without as well, with plans to craft one (with attachment points for a splitter) once things cool down a bit. At that price it would just be easier to purchase.

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Originally Posted by Yamahaman444

Wait. Synthetic or Dino? Hahahahahahaha

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Dino oil and synthetic antifreeze, FTW!

B.

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Originally Posted by Yamahaman444

Also, I typically run the car with the AC on, so that both fans are on, helping out cooling I believe.

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Huh?!?

The theory of running both fans when driving at Auto-X speeds is valid (not needed and not helpful at track speeds).

But turning on your AC? Never, ever. Assuming your AC is charged and functioning, there is no better way to overheat a Miata than to add load to the engine and preheat the air with a hot condenser.

For Auto-X, find a way to run both fans WITHOUT engaging the AC compressor. People usually wire the AC fan to turn on with the normal cooling fan.

Also, your OEM temperature gauge is a liar. It's non-linear and will stay in the middle even as your water temp is creeping past 220. By the time it's indicating hot, you're HOT!! This is on purpose to minimize warranty service. Install an aftermarket temperature gauge if you want to know the truth.

Just one more data point before throwing $$ at it. Check you main fan. This fan is knownto fail at this kind of mileage. To see it spinning is not enough. It gets weak with age. Wear a heavy and try to stop it. If is stops easily, it is bad and it is your over heating issue. Also, check your secondary fan. If it doesn't kicks in when the a/c is on, you will over heat b/o the extra heat from the condenser and extra load. Don't ask how I know! :-(

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Originally Posted by hornetball

Huh?!?

The theory of running both fans when driving at Auto-X speeds is valid (not needed and not helpful at track speeds).

But turning on your AC? Never, ever. Assuming your AC is charged and functioning, there is no better way to overheat a Miata than to add load to the engine and preheat the air with a hot condenser.

For Auto-X, find a way to run both fans WITHOUT engaging the AC compressor. People usually wire the AC fan to turn on with the normal cooling fan.

Also, your OEM temperature gauge is a liar. It's non-linear and will stay in the middle even as your water temp is creeping past 220. By the time it's indicating hot, you're HOT!! This is on purpose to minimize warranty service. Install an aftermarket temperature gauge if you want to know the truth.

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Are there any aftermarket gauges that the stock wires just harness right in and fit in the OEM gauge spot in the dash?

Ahhhhh that's what I read. No AC because it preheat the air. Yup yup. Thanks for that!

No issues in a few weeks. We'll see how autox this weekend goes

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Originally Posted by Yamahaman444

Are there any aftermarket gauges that the stock wires just harness right in and fit in the OEM gauge spot in the dash?

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I've seen some people get pretty crafty with putting aftermarket gauges into the stock gauge pod. I just pull the radio (can't hear it anyway) and mount gauges in that location on my Miatas. Also, the 2 1/16" gauges are a perfect fit into the eyeball vents.

The fan on a Miata only generates as much air as driving 12 mph. So if you're overheating on-grid or in stop/go traffic, then it can be the fan. If you're under 12 mph, usually the RPMs are very low and the fan can handle that.
Once you're moving more that 12mph, then it's not the fan.

I saw a NA with its hood up on the way home the other day on I35W north of 114 and stopped to help. It was overheating. She'd been downtown in stop and go traffic, no issues. Her fan was working.
When she got on I35W, the fan was no longer of consequence, but the missing bottom tray was. All the air at 65 mph was going under the radiator. Needless to say, at 65 mph she was probably running 3,700+ rpm. The fan couldn't handle that.

Rogue is right about the pressure test. Most of the autoparts stores will loan you the tester.
Does the '97 have an oil cooler, always check those little hoses from the back of the block and throttle body. Even though the previous owner says he changed all the hoses, those don't usually get changed as they're a PITA to get to.

Search Miata.net, there's a fix for the temp guage to make it linear. Or just get the kit from Advanced Autosport. I have their oil pressure.

OR get a ODB-II reader, it will show the water temp. I have a Bluetooth adapter and the Torque phone app. Works great!

I've got a couple of used belly pans I'll let go cheaper than new if you want to grab one quickly/cheaply.

Awesome guys. See, this is what I wanted.

I'd love a used belly pan, thanks. Will PM soon

Hoping to get a pan from Ozmdd as soon as he pms back. Had no issues with overheating while doing Autox, even while in the 95 degree heat. I think everything is alright but I know the belly pan will help more.

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Originally Posted by Yamahaman444

Hoping to get a pan from Ozmdd as soon as he pms back. Had no issues with overheating while doing Autox, even while in the 95 degree heat. I think everything is alright but I know the belly pan will help more.

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Belly pan isn't that important at autocross speeds. Much more critical at highway speeds where air tends to compress under the nose of the car. This pressurizes the engine compartment if there is no belly pan, which impedes radiator airflow. The R-package front spoiler also helps with this issue (you can find cheap knockoffs on E-bay).

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Originally Posted by Yamahaman444

No undertray. I read it helps with airflow especially at lower speeds, correct?

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You need one. This is where I would start. Speaking from experience here.

Thus why I am getting one. Also thinking about getting some turn signal vent conversions? For the front indicators.

Turn signal vents are primarily for cosmetic purposes. For cooling, make sure your radiator is up to the task (sufficient capacity and not old) and then it's all up to airflow through the radiator. That means sealing the "mouth" to keep air from dodging under or around the radiator. It also means a belly pan to help smooth flow and create a pressure differential from the front side of the radiator to the back side. Turn signal vents add pressure to the back side of the radiator -- not what you want. If you want vents for airflow, you want hood vents, which are obviously more difficult to do.

Ozmodd, is a pan still available? Still interested in buying.