NA8 overheating on track

BARWICK · Postby **BARWICK** » Wed Nov 18, 2015 7:28 pm

Hi guys,
took my stock NA8 MX5 out on a trackday at Mallaha and found i was unable to get 2 consecutive hot laps with out the temperature gauge going right up to the hot mark. Even when i backed off for a couple of laps to get the temp down as soon as i started pushing it again it would just skyrocket.

I had flushed the coolant including the block, changed the thermostat and even removed the front indicators to increase air flow in preparation for the track day.

Is this a common problem with the standard cooling systems on the NA models?

If so what upgrades have you done to solve this problem?

Thanks in advance guys

Kind regards
Greg

Dweezle · Postby **Dweezle** » Wed Nov 18, 2015 7:34 pm

Removing the intake assembly will actually hurt your cooling.

You need air flow through the radiator not around it.

Common overheating issues in these older 5s are stuck thermostats, deteriorating radiators (brown and faded), dying water pumps and no Undertray.

I bet your radiator has had its day.
Cheap Alloy Ebay jobs usually do the trick for around $120.

davekmoore · Postby **davekmoore** » Wed Nov 18, 2015 7:39 pm

Yup, removing front indicators will probably increase under bonnet air pressure, thus allowing less air to come in through the radiator. If it goes to the end of the temp gauge there's a real problem waiting to happen right there at that moment. Fingers crossed it hasn't already happened.

Magpie · Postby **Magpie** » Wed Nov 18, 2015 7:44 pm

Is the undertray installed?

gslender · Postby **gslender** » Wed Nov 18, 2015 7:54 pm

Also, make sure she's properly burped as air in the system will cause over boiling.

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Postby **beavis** » Wed Nov 18, 2015 9:51 pm

No it is not common. A stock NA8 shouldn't overheat at the track. You shouldn't need to do any upgrades to make it work. There is something wrong.
Could be:
faulty thermostat - which you said you already replaced
crap or lack of coolant - which you said you already replaced
clogged/old radiator
waterpump
air in the system

Steampunk · Postby **Steampunk** » Wed Nov 18, 2015 10:25 pm

- do you have the radiator air-redirection plate installed?

- as mentioned, do you have the engine undertray fitted?
- does your heater work and blow hot air?, indicating that your heater hoses hasn't been bi-passed.
- do you have a grille fitted in the bumper "mouth"?
- is your thermostat in good condition?

Guran · Postby **Guran** » Wed Nov 18, 2015 10:35 pm

Try running without a thermostat. I've found that even brand new genuine Mazda thermostats can be faulty from day one. If it goes ok without a thermostat then you know where the problem is and just need to keep trying new ones until you find one that works properly.

manga_blue · Postby **manga_blue** » Wed Nov 18, 2015 10:49 pm

I ran a couple of thousand laps in a lightly modified NA8 with its original radiator and standard cooling system and never had problems.

Radiator needs to be clean inside and out. All air needs to flow through the radiator and not around it. The undertray must be on. Thermostats and radiator caps slow down and die. The coolant needs to be fresh and as low as you can go on ethylene glycol - use Redline Water Wetter and no glycol if it's never going to get frost. Water pump needs to be working OK. All the hoses, including all the little ones which hide in front of, under and behind the inlet manifold should be checked for perishing, softness, brittleness and leaks - replace the lot if a few are bad.

If you've got all that under control and it still overheats then remember that retarded ignition, lean mixtures and blocked exhausts can all sap power and cause overheating. Is it a bit gutless?