- My model of MX-5 is: 2008 2.0i NC
- I’m based near: Berkshire
- I’m looking for technical help or recommendations on cooling!!
To give a back story, on Friday I was driving round a roundabout when my back end suddenly span out. When I got it back under control I looked down to find a check engine light on. After pulling over in a car park a couple hundred metres down the road I opened the bonnet to find coolant had exploded all over my engine. Turns out the car had overheated causing the coolant to leave its tank (when every other time I’ve driven the temp has sat perfectly in the middle, no matter how hard, how far, or how hot it is outside.)
I’m planning to replace the thermostat so am wondering if anybody knows of any good one to try (if there are differences between them)?
The other thing is whether anybody has any other ideas on what might have caused this? (The car couldn’t make it out the car park without overheating (after the coolant had been topped up) so I’m assuming something is blocking it off, hence replacing the thermostat)
In case any extra info is wanted, it’s a 2008 2.0i with everything stock.
Edit: all solved! Thermostat went so replaced it and the car is working as normal again!
check the coolant expansion tank. i have a feeling it cracked under pressure and i reckon that’s where the coolant came out.
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Agreed.
This is a well known possibility.
Two solutions exist if the tank has failed
- fit a NEW (not second hand) Mazda plastic tank, and it should (hopefully) last another decade.
- Fit an aluminium tank, a couple on the market, both more expensive, but well made and will/should outlive the car.
I fitted the Davefab version because it’s black and has a sight-glass to check the coolant level. As shown here,
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I’ll have a look, thank you! Only thought is why would it still be overheating if coolant has been topped up?
Has it been properly burped? ALL air purged?
Is lots of steam coming out the exhaust? (Head gasket failure).
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Personally i would not touch dave fab stuff with a barge pole hence why i went with a moroso expansion tank. (Wouldn’t rate much cheap Chinese stuff as well).
On the plus side apart of being functional i now need to clean my engine with all the bling under the bonnet 
)
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Haven’t seen any steam coming out the exhaust. Could be that there’s still some air in there, is there any specific way to get it out?
I like the strut brace too! I’ll have a look into it, would be nice it get a bit more shine under the bonnet anyway!
Nicer looking one (and may be also stiffer) at mx5 parts that im also tempted of buying.
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Under bonnet bling is a must for an NC 
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next club meeting I’m taking a cloth and the autoglym engine bay washer. will let anyone clean mine cuz I cant be asked
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Very nice! I’m feeling a bit jealous now!
I can clean an engine for the price if four tyres! Offer will always be there!
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Here is an extract from the (US) manual page on coolant replacement.
- Refill the coolant into the coolant reserve tank up to the F mark on the tank.
- Install the cooling system cap.
CAUTION:
If the water temperature gauge rises too high, stop the engine and decrease the water temperature to prevent overheating. Then, verify the malfunctioning part and repair or replace it.
If the engine coolant level in the coolant reserve tank is below the L mark during engine coolant air bleeding operation, stop the engine, and after the engine coolant temperature decreases, add engine coolant. Then, resume the engine coolant air bleeding operation.
- Start the engine and warm up the engine by idling.
NOTE:
If the accelerator pedal is depressed continuously for a specified time, the engine speed may decrease to the idle speed. This is due to the fuel cut control operation, which prevents overheating, and it does not indicate a malfunction.
- After the engine warms up, perform the following steps. At this time, be careful of the coolant temperature to prevent overheating.
a. Run the engine at approx. 2,500 rpm for 5 min.
b. Run the engine at approx. 3,000 rpm for 5 s, then idle.
c. Repeat step (b) 4—5 times.
- Stop the engine, and inspect the coolant level after the coolant temperature decreases. If it is low, repeat steps 7—10.
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Not by the book, but a burping method which has worked for me and others on here is to raise the front wheels (or park on a decent slope), heater full on and run at varying revs, also giving the heater hoses a good squeezing and topping up fluid as necessary. Very satisfying when you get a good ‘burp’ 
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Hi, This is my first reply to a forum topic!
I also have a 2008 2.0l NC Niseko. It’s coming up to 98k miles.
I’m wondering if the failure of the plastic coolant expansion tank is a common problem.
So far the car has been ultra reliable. Is the replacement of the tank something I should be seriously considering in the near future?
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Not heard of many failed, if any on this forum. It seems from an article posted on another forum (maybe USA) they can fail in warmer climates around the plastic welded neck on the tank.
I’ve got a metal tank fitted, got it at a reasonable price, well made, despite remarks they are sub standard.
On my last NC, now transferred over to the current one.
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I have to say my comment was on a purchase of a davefab oil catch can, and in particular on their engineering decision to thread tap a 2mm aluminium sheet with aprox 20mm emptying plug.
Obviously the threads would strip and the canister would not hold vacuum - and that was around 200 quid worth of hard earned cash
Based on that i made the personal desision to stay away from their products. I have no experience in regards to their other products - which may as well be ok - the just wont take my custom and I’m not willing to take another chance at that.
Before changing anything, do the logical checks:
Assuming it is an old tech wax expansion type, put it the thermostat in boiling water to see if it opens , also check the fan is switching on. If any of the cooling system is controlled by electronic sensors, try an OBD2 diagnostic test.
If those are ok, flush out the radiator just in case the waterways are blocked.
Finally pressure test the cap and the system at the filler, preferably when the coolant is warm. If that is all ok sounds like a blown head gasket, unfortunately .
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