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Old 04-22-2012, 03:33 PM   #1
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Default Overheating very quickly

So I've read countless threads on overheating and I realize that without an undertray (which I don't have) and a stock radiator (which I have) and a nice big intercooler blocking the radiator it is going to run hot but I just went on a drive where before I left the temp was 144* and within two minutes of driving without being in boost the temp was all the was to 235*+. I just ordered an ebay radiator in optimism that it would fixy problem but I'm not sure. I'm also running bumperless and hoodless if that makes any difference. I would say I am probably at about 80/20 water to antifreeze...
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Old 04-22-2012, 04:19 PM   #2
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bumperless? hoodless? undertrayless?

I have no doubt you're also running ductless, and possibly working-fanless.

You don't need a new radiator - you need air to flow across it. In it's current state, you have no airflow. You might as well do a radiator delete - just connect the water out on the engine back to the water in. Same result, less weight, AND you won't be wondering why you're running hot because it'll be less mysterious to you.
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Old 04-22-2012, 04:27 PM   #3
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... undertray (which I don't have) ....stock radiator (which I have) ...also running bumperless and hoodless if that makes any difference.
Thes above are problems. Fix them and win at life.

Search "radiator ducting" here on MT and read... its pretty important. The stock Miata cooling system can be marginal at best. Add boost, subtract airflow management (ducting) and you have a recipe for disaster. Your higher capacity ebay rad may cause the car to take longer to overheat, its still going to overheat.
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Old 04-22-2012, 04:31 PM   #4
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Well I have the bumper but it overheated while it was on as well. Both fans are on constantly. But yes i'm in the market for a hood, and you think just ducting will make the massive difference? I just thought that if I was cruising 60 there should be enough air to at least cool a little..
Also I might point out that it was overheating at idle as well so I can't see ducting being a problem there?
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Old 04-22-2012, 05:00 PM   #5
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At idle? Humm... have you burped your coolant system? You might have a big *** air bubble in the block maybe? Are you loosing coolant anywhere?

Hows your timing/afrs? Have you tried anything to double check your coolant temp? I see you are on a MS2... even with as inaccurate as the stock gauge is, does it jive with Megatune/Tunerstudio?
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Old 04-22-2012, 05:07 PM   #6
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I didn't think about air bubbles. I took the turbo off to port the wastegate and a lot of coolant drained out then. Timing, afr, and the gauges were all good and in sync. I'll flush and refill the radiator and see how that goes
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Old 04-22-2012, 05:07 PM   #7
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Air is very lazy. In that if it doesn't have to go through your rad/condenser/intercooler, it won't. It will back up to the point of going around your car instead of though it. If you look there is plenty of space right by the sway mount brackets to flow tons of air bypassing the radiator. That's if you have an under tray. If you don't there's no control. No hood and there's no chance of creating a lower pressure in the engine compartment, thus pulling air through the radiator and into/out of the engine area.

Bottom line: get a hood, some ducting, and under tray= no over heat.

Be sure to check the coolant system too. Thermostat, heater core flow, leaks, and cap.

Im gonna be working on an aluminum under tray soon. If I have enough aluminum I'll make two. Maybe one for sale.
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Old 04-22-2012, 05:24 PM   #8
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Im gonna be working on an aluminum under tray soon. If I have enough aluminum I'll make two. Maybe one for sale.
Looking for a hood as we speak. And hope i'll have $ when you do!
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Old 04-22-2012, 05:31 PM   #9
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If your car is getting that hot with regular driving there is something else going on beyond the lack of a hood/undertray/bumper. I've done plenty of driving with no undertray at +300whp with a stock radiator in the middle of summer in south FL and not overheated. I don't feel like the hood or bumper would change that all too much.

If the fans are on, most likely the thermostat is stuck closed, or there is a massive bubble (but in my experience they seem to work their way out after the car gets warm the first time). Smart money is on the thermostat. Make sure you get a 180 degree stat.
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Old 04-22-2012, 07:20 PM   #10
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I removed the bumper mouth plastic that closes the area between the bumper and the radiator once when naturally aspirated and it was overheating within a couple of miles.
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Old 04-22-2012, 08:28 PM   #11
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Well turned out to be my thermostat stuck closed. Now runs steady at 180*. I guess it won't hurt to have the ebay radiator anyway
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