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From my experience in my MX it seems to hate hills, I have run it up Nebo quite a few times and never had issues with heat but on the steeper sections like coming back up Mt glorious and going onto nebo from Samford it always seems to love to overheat. I have installed a 52mm ASI radiator on it and still have the same issues. Lately i have been reading that the cooling on the earlier 5's was questionable and a "coolant re-route" has been made to combat the problem. My question is, is do i give up and and avoid steep hills or would a coolant re-route fix this?

What a people's experiences with the cooling system's of MX-5's?

It sounds like there's an issue somewhere to be honest.

A stock standard MX-5 shouldn't be overheating that easily.

I could be wrong but the coolant re-route were more for people who have fiddle with there engines.

Standard engines shouldn't have much trouble, if any, keeping the temperature stable. Mine just has the 42mm ASI, with no undertray, and I've never seen the gauge budge above half way (except once when I was stuck in traffic and I didn't have the radiator fan installed...)

Maybe there's a blockage somewhere that's restricting your coolant flow.

Sonds like you have a flow restriction in your cooling system. First thing is to remove your thermostat and test that it opens at the correct temperature (82C) and is fully open at 95C. Look for bright polished marks on it, which is a sign of a sticking thermostat. Replace with a new thermostat if it's sticking. Cheap fix!

Go to an auto store and buy a new thermostat and radiator flush.

Run the flush + distilled water through.

Drain it, which will probably be gross as it dissolves various deposits.

Check the new thermostat as Guran has explained, if it's all good put it in.

Put new coolant in, and bleed it properly!

Coolant re routes are boss, and revert the engine back to how Mazda designed it, but it sounds like you have a problem that needs addressing before you mod it.


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Somethings funny there.
I have a stock radiator and a few little mods here and there, and I run up Mt Dandenong most days and don't even get half way on the temp gauge

emily_mx5 wrote:
Coolant re routes are boss, and revert the engine back to how Mazda designed it, but it sounds like you have a problem that needs addressing before you mod it.

Unless you have a later model in which case a re-route will make things worse.

Agree with others, your car should be okay with hills unless you are doing something like driving in a high gear with your foot on the floor and the engine labouring.

Car should have no heating problems if you are driving at legal speed limits, even through hills.

but yeh, test thermostat and reroute if your budget affords / want piece of mind

Something possibly notable- I blew a radiator hose a while back, and replaced the thermostat first thinking it could be that.
Eventually I replaced the radiator and all associated hoses, and the temp gauge sat a touch below half way, compared to the perfect half way it used to sit at.
The thermostat was like 5degrees different in terms of the point at which it opens, and with new hoses and radiator the temp on the gauge fell a very noticable amount.

Small things obviously have a pretty big impact in terms of cooling, so double check everything, make sure there's no pinhole leaks in any pipes that could cause you to lose pressure

I've tracked mine for years with its original Mazda radiator. The only time I had an issue was at a track day at Winton just before Black Saturday when it was 46 in the shade and the thermostat was playing up. I did a coolant route last year and that takes out any fluctuation whatsoever in the temps and it's still on the old radiator. 52mm is overkill.

You could also have a problem with the water pump. If there's ever been any corrosion then there's a chance that the pump impeller blades are not as big as they used to be. As Guran and Emily suggested, do the flush and thermostat things first. If overheating is still a problem then check the coolant flow. Drain off a couple of inches from the radiator, take the cap off and idle it until the thermostat opens. Then look at the water inside the radiator. You should be able to see it flow fairly briskly from left to right over the tops of the core, even at or near idle speed.

emily_mx5 wrote:Go to an auto store and buy a new thermostat and radiator flush.

Run the flush + distilled water through.

Drain it, which will probably be gross as it dissolves various deposits.

Check the new thermostat as Guran has explained, if it's all good put it in.

Put new coolant in, and bleed it properly!

Coolant re routes are boss, and revert the engine back to how Mazda designed it, but it sounds like you have a problem that needs addressing before you mod it.


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When i bought the car in july i had the thermostat and radiator cap replaced due to it actually spilling out all of its coolant and therefore being abandoned on Nebo for a while as i waited for someone with a bit of water to help out, so i hope it's not the thermostat already. i will get some flush and distilled water and run it though properly and might as well get some new pipes as well as the bottom one is becoming a little brittle.

oh and it is when it is floored and trying it's going up the hill as fast as possible - so is that an unfixable issue on these cars or do you need a highly modified cooling system?

Thermostats are unreliable, that's just how they are.

Sometimes they dont work properly straight out of the packet.

Dann

angusis2fast4u wrote:oh and it is when it is floored and trying it's going up the hill as fast as possible - so is that an unfixable issue on these cars or do you need a highly modified cooling system?

No, what we're saying is that a stock MX5 cooling system in reasonable condition can handle that sort of thing easily, every time. That's what these cars were built for. There's something wrong with yours. As Dann said, you could have bought a crap new thermostat, or your 52mm radiator doesn't flow properly, or your water pump is stuffed, or the whole system is blocked up with gunk, or maybe one of the hoses has gone soft or delaminated inside so it collapses and blocks under suction, or whatever ...

You shouldn't need any cooling system modifications if it's working.
An unmodified MX5 shouldn't overheat, it shouldn't matter if it's sitting still, belting along at 200kph, or going up a hill. (I'm talking real life here, not doing 200kph for an hour straight, or crawling up a 45degree slope for an hour)

When you add turbos and other stuff that can generate heat, or reduce the airflow (ie: number plate in the intake), then there's potentially issues.

angusis2fast4u wrote:oh and it is when it is floored and trying it's going up the hill as fast as possible - so is that an unfixable issue on these cars or do you need a highly modified cooling system?

As all the others have said, the standard cooling system works fine over any hills that have a road if it is working correctly. There is a problem somewhere with yours or your engine is overheating through detonation etc.