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Old 06-01-2010, 02:42 AM   #1
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Default [NB] Overheating issue with AC

Alright so I purchased my first Miata almost 2 weeks ago in Washington state and drove it back home to Texas. I'll have the list of mods in a bit but it's supercharged and supposedly putting down 250 hp to the wheels according to the previous owner. Anyway, I had no issues cruising 70-80mph most of the way. I didn't have to use the air conditioning until I hit Arizona and that's when the temperature gauge on the stock cluster started rising past 12o'clock and close to the 'H'. For the rest of the trip I had to leave the AC off or bring my speed down in order to use the AC. I've driven it around town here in Texas where it's currently 90 degrees during the day and if I'm putzing around town doing 30-45mph I can have the AC on full blast as long as I keep my rpm's down below 4k and it won't overheat.

My goal for this Miata is to make it my track car so it will definitely be pushed at the track and I will definitely need tip top cooling for it. AC is a must in the Texas heat for traveling to and from the track.

2000 Miata LS, 5spd, 112k miles
Flying Miata Coolant Reroute Mod
Oil Filter Relocation Kit
Eaton Supercharger (forgot which model)
10psi pulley
131mm crank pulley
Hydra Nemesis 2.5 EMS
550cc Injectors
Intercooler with heat shield up top
Undercarriage metal guard

Yesterday I drove about 15 miles along 30-50mph roads, AC cranked on full blast and I kept my revs below 3500 and the temperature needle didn't move past the 11:30 position. After that 15 miles I stopped and then continued again along the same roads but played around a bit keeping the revs up in the 3000-4500 range trying to simulate the highway driving (cruising at 80 left the rpms around 4200) and that's when the car started to overheat which is when I pulled over, popped the hood and the coolant was bubbling in the overflow reservoir.

I'm pretty sure the thermostat is fairly new due to one being included in the Flyin' Miata coolant reroute kit the previous owner put on but I could always test it again I suppose. Friends have been suggesting it's either (1) bad AC causing excess heat (2) water pump possibly not pumping as much as it should (3) car is running lean causing excess heat (4) being that the thermostat is a couple of inches away from the head now due to the reroute mod it might actually not be heating up the same time as the head causing heat issues. I know that both fans run when they kick on so they must have been wired in parallel. It's possible that the intercooler may be blocking airflow to the radiator.

Just wanted to let you know as well that cruising at 80 on the highway without AC the car was perfectly fine. Turning on the AC is when the temperature started climbing. I'm kind of stumped at the moment and not sure which direction to head in for debugging this issue. Has anyone encountered a similar issue? I thought about going to the Koyo 37mm radiator (can't do the 55mm since I have the large Eibach swaybars) but my friend told me that solution would only delay the car from overheating. Is this true?

Pics for reference...
After we rerouted the long coolant hose under the strut brace (didn't fix it)
http://i389.photobucket.com/albums/o...ute/photo2.jpg
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Old 06-01-2010, 03:46 AM   #2
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Time for a radiator....... Might take a look at the PRC unit all the V8 guys are using.
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Old 06-01-2010, 04:05 AM   #3
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think you mean m-tune reroute, fm don't make one, they sell the m-tune kit.

i had the same set up with out a reroute but with a pwr and i had a problem not getting hot enough in weather under 80*

get a pwr and duct your radiator better.

edit: i just looked at this photo http://i389.photobucket.com/albums/o...aEngine013.jpg you have what i'm guessing is a water hose going from your dummy throttle to some were if that's water going into you dummy body then cap it, your just reheating the air after the intercooler cools it. not sure where your getting water from and where it's going to after words but i'm betting it's not needed.
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Old 06-01-2010, 05:17 AM   #4
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That's just so the IAC uses metered air but it can probably be replaced by a small filter at the IAC instead since he is running the MAP-based Hydra.
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Old 06-01-2010, 05:50 AM   #5
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Next step is RAD for sure. What percent mixture coolant/water are you running? Perhaps try some redline water wetter? Also how well is it shrouded, pics?
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Old 06-01-2010, 08:26 AM   #6
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I just so happen to have a PWR rad from my NB that I pulled out.

Frank
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Old 06-01-2010, 08:37 AM   #7
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Make sure you coolant/water ratio is not too high. You could probably run a 70% Water 30% Coolant Mix. Also make sure the T-Stat in the reroute has a 1/8 holes drilled in it.

Hope this helps,
Marc
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Old 06-01-2010, 10:22 AM   #8
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Quote:
Originally Posted by jeff_man View Post
think you mean m-tune reroute, fm don't make one, they sell the m-tune kit.
Nah, Flyin' Miata actually makes a kit... http://www.flyinmiata.com/index.php?...umber=09-60000 I took that spring out of the old hose when I rerouted it under the strut tower brace. Edit: Wow, I just looked at the M-Tune kit and they're almost identical. BUT the metal piece of the back of the engine denotes "Flyin' Miata" on it.

Quote:
Originally Posted by jeff_man View Post
edit: i just looked at this photo http://i389.photobucket.com/albums/o...aEngine013.jpg you have what i'm guessing is a water hose going from your dummy throttle to some were if that's water going into you dummy body then cap it, your just reheating the air after the intercooler cools it. not sure where your getting water from and where it's going to after words but i'm betting it's not needed.
That's actually an air-line, we shortened that as well to get rid of the kink on the right side of the enginebay. Like saboteur said, which is actually what my friend told me, is I can cap that line at the air filter side and run a catch can on the dummy throttle side.

Quote:
Originally Posted by Fireindc;
What percent mixture coolant/water are you running?
Currently in there is a new stock radiator that the previous owner installed. I'm running a 70/30 distilled-water/coolant mixture after I flushed whatever the previous owner had. It also seems like he got a set of aftermarket fans that are bolted to a this sheet of metal that sits a good 1-2 inches away from the radiator. Doesn't seem to be affecting idle temperatures though.

I haven't heard of the PWR radiator. Is it a bolt on replacement or custom? What kind of fans are attached to it?

I'll get closer photos of the front intercooler, AC condensor, and the radiator tonight when I get home from work.

Last edited by RavynX; 06-01-2010 at 10:44 AM.
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Old 06-01-2010, 10:45 AM   #9
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That sure looks like the M-tuned coolant reroute to me.

Jeff knows what he's talking about on cooling, he's been tracking a supercharged NB for about 3-years. You need to duct the radiator so air cannot go around it, you need a real radiator in general for when you start tracking it, and run 10% anti-freeze (good to around 10*f freeze protection).
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Old 06-01-2010, 10:56 AM   #10
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Quote:
Originally Posted by hustler View Post
That sure looks like the M-tuned coolant reroute to me.

Jeff knows what he's talking about on cooling, he's been tracking a supercharged NB for about 3-years. You need to duct the radiator so air cannot go around it, you need a real radiator in general for when you start tracking it, and run 10% anti-freeze (good to around 10*f freeze protection).
Oh, I think I misread what jeff said, me mentioned FM doesn't make one but they sell the m-tuned kit. I guess FM just stamps "Flyin' Miata" on the part connected to the motor of the m-tuned kit.

How do people go about ducting the radiator?
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Old 06-01-2010, 11:13 AM   #11
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Quote:
Originally Posted by RavynX View Post
Oh, I think I misread what jeff said, me mentioned FM doesn't make one but they sell the m-tuned kit. I guess FM just stamps "Flyin' Miata" on the part connected to the motor of the m-tuned kit.

How do people go about ducting the radiator?
Take a roll of 2-4mm plastic and seal the mouth of the bumper to the radiator so no air can go around it. Its that simple and absolutely required for tracking a car. I have a "coolradiator.com $150 pos) and I can run all day long at 100*f ambient temps and the gauge never goes above 180*f on engine water temp, and the fans never turn on.
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Old 06-01-2010, 11:54 AM   #12
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Quote:
Originally Posted by RavynX View Post
Friends have been suggesting it's either
(1) bad AC causing excess heat A joke, right?
(2) water pump possibly not pumping as much as it should Probably not or you would be overheating more when it was spinning slower.
(3) car is running lean causing excess heat Running lean and/or with a retarded spark will cause more heat to be released to the cooling system, but not a lot more.
(4) being that the thermostat is a couple of inches away from the head now due to the reroute mod it might actually not be heating up the same time as the head causing heat issues. If the thermostat doesn't have water flowing past it when closed it will not see the engine's temp and open properly. This is why the aforementioned holes are important.
I know that both fans run when they kick on so they must have been wired in parallel. It's possible that the intercooler may be blocking airflow to the radiator. If the factory plastic bumper inlet sealing/ducting is not present and has not been replaced with a similarly effective sealing arrangement you will have trouble. This applies to unmodified cars as well.

Just wanted to let you know as well that cruising at 80 on the highway without AC the car was perfectly fine. Turning on the AC is when the temperature started climbing. Twenty degrees above ambient might be too much for the efficiency level of the stock radiator at whatever ambient temp was.
I'm kind of stumped at the moment and not sure which direction to head in for debugging this issue. Has anyone encountered a similar issue? Yes. The stock cooling system is inadequate at stock power levels on hot days with the A/C running either when parked or autocrossing.
I thought about going to the Koyo 37mm radiator This would increase your cooling capacity somewhat and might be adequate for a supercharged street car.
(can't do the 55mm since I have the large Eibach swaybars) Then you should buy a different bar, move the swaybar mounts, get slim fans, or something that will allow you to run a proper track car radiator for a southern climate. I recommend the 52mm Mishimoto.
but my friend told me that solution would only delay the car from overheating. Is this true? Yes. It would delay the car from overheating for the rest of the time you own it.

Pics for reference...
After we rerouted the long coolant hose under the strut brace (didn't fix it)
http://i389.photobucket.com/albums/o...ute/photo2.jpg
Why is that hose reaching all the way around the front of your engine? Do you have a closer pic?

The other possible problem that you have not mentioned is the possibility of air trapped in the head because of the reroute not being able to be burped at its highest point.
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Old 06-01-2010, 12:19 PM   #13
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Hey, RavynX, welcome to the forum and to Miata ownership.

I'm guessing that the supercharger is an MP62, and the kit was packaged by a company called BR Performance out of South Carolina. They don't exist anymore.

I think the 'undercarriage metal guard' is a knockoff of this.

Please go to "Edit Your Details" and insert your city. Texas is a big place. Plus, that'll make it easier to send you to the right performance shop.

For now, all you need to upgrade is the radiator. The stock rad is insufficient for forced induction on the track. I use a PWR (great radiator from Australia) but there are others just as good. Personally, I use pure distilled water and a sip of Water Wetter by Redline.

One more thing: you should find out what size your pulleys are (in millimeters). That info will come in handy later. Looks like Flyin' Miata helped out with the build, maybe they have the specs on file.

Here's my ****:
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Old 06-01-2010, 12:34 PM   #14
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I had the same overheating with A/C on a trip across I90 on a 33 Celcius, humid day.

Stock Rad, BRP 62, no reroute, no intercooler, no funky fairings to direct the air into the rad.

I was able to eliminate the overheating by removing the front license plate (required in Ontario, Canada) which was installed in the mouth.

Spent the day at the track in Shannonville, On yesterday, it was hot. No overheating problems.

YMMV.
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Old 06-01-2010, 01:58 PM   #15
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Quote:
Originally Posted by RavynX View Post
Nah, Flyin' Miata actually makes a kit... http://www.flyinmiata.com/index.php?...umber=09-60000 I took that spring out of the old hose when I rerouted it under the strut tower brace. Edit: Wow, I just looked at the M-Tune kit and they're almost identical. BUT the metal piece of the back of the engine denotes "Flyin' Miata" on it.
Most everything they sell is sourced.
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Old 06-01-2010, 02:48 PM   #16
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Originally Posted by Double O 86 View Post
Why is that hose reaching all the way around the front of your engine? Do you have a closer pic?

The other possible problem that you have not mentioned is the possibility of air trapped in the head because of the reroute not being able to be burped at its highest point.
That was there when I bought the car. That hose was actually kinked on the right side of the enginebay but we shortened it and rerouted it. I plan on capping the right side off and putting an oil catch can connected to the left port. As for the air being trapped, we had the front jacked fairly high on jack stands so that we could properly burp the system. I think we let it burp for a good 20 minutes; does it need longer?

Quote:
Originally Posted by Double O 86 View Post
Hey, RavynX, welcome to the forum and to Miata ownership.

I'm guessing that the supercharger is an MP62, and the kit was packaged by a company called BR Performance out of South Carolina. They don't exist anymore.

Please go to "Edit Your Details" and insert your city. Texas is a big place. Plus, that'll make it easier to send you to the right performance shop.

For now, all you need to upgrade is the radiator. The stock rad is insufficient for forced induction on the track. I use a PWR (great radiator from Australia) but there are others just as good. Personally, I use pure distilled water and a sip of Water Wetter by Redline.

One more thing: you should find out what size your pulleys are (in millimeters). That info will come in handy later. Looks like Flyin' Miata helped out with the build, maybe they have the specs on file.
Thanks for the welcome! I updated my profile info from the '06 s2k to the Miata. I still have the s2k, but I'm tracking the Miata. I'm from San Antonio so I'll be frequenting H2R a bit. I can't wait to make it out to TWS, MSR-H, and MSR-C.

Since I have that thick Eibach swaybar I can probably only do the Koyo 37mm radiator. How is the fitment with the PWR radiator? Can you keep your AC unit with that one? Would you happen to know if the current FM fan shroud setup is worth keeping or is it a hindrance with aftermarket radiators? Not sure if I'd have to replace the fans I have now if I went Koyo or PWR.

According to his excel sheet of mods/repairs that previous owner gave me...
110 mm s/c pulley
131 mm crank pulley

Should I keep the stock thermostat with the M-Tuned reroute, drill holes in it, or go for the 160 degree thermostat?

Last edited by RavynX; 06-01-2010 at 03:16 PM.
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Old 06-01-2010, 03:09 PM   #17
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I'm running the 1.125" RB front bar and a 53mm Koyo. i doubt that the eibach bar will cause any interference with a 53mm rad.
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Old 06-01-2010, 03:14 PM   #18
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Keep the 180* thermostat. Lowering the t-stat temp will not increase the thermal capacity of the cooling system.
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Old 06-01-2010, 03:18 PM   #19
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Originally Posted by tann3r View Post
I'm running the 1.125" RB front bar and a 53mm Koyo. i doubt that the eibach bar will cause any interference with a 53mm rad.
What type of fans are you running with your 53mm radiator? You're Colin from TrackJunkies, right?


Quote:
Originally Posted by hustler
Keep the 180* thermostat. Lowering the t-stat temp will not increase the thermal capacity of the cooling system.
Sounds good, thanks.
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Old 06-01-2010, 03:26 PM   #20
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I sure am. and i'm running the stock fans with some fuel line to seal the fan shoud to the rad better.
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