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Hello gents.

I noticed today that my engine temp needle was about 3/4 the way up the range. Pulled her straight home and checked everything my small amount of knowledge allowed me to: The coolant still looks green tinged with no gunk seen, the overflow reservoir is halfway between the full and empty line. I cant see any coolant leaks and havent noticed any since ive owned the car (2 odd months) and she's 1000 KM's fresh from a 100k full service with MX5-mania. I left the car idling for about 10-15 minutes and it would stay steady on 12 o'clock, the radiator fan would start spinning too. I gave her a quick 5 minute drive around my street with modest use of the throttle (never above 3K revs) and at the tail end of that session the needle began creeping past dead centre up towards 3/4.

Any ideas? should I perhaps try a coolant flush (though it was done no more than a month ago by the maina guys)?

new thermostat & radiator cap maybe

further tests:

- let car idle for 10 minutes with rad cap off: no fluid movement
- turned on heater at full blast: warm air as per normal. slight fluid drop from radiator
- touched hoses to and from the thermostat itself: hot to touch. seems like the 'stat is fine.

havent taken the thermostat out though, looks like theres a gasket between the flanges that I dont have time to find if I need to drive the car somewhere.

You should be seeing a swirl in the radiator I would've thought. Can't say I've specifically looked for it on the mx5 yet but sounds like the water pump might have died if that's all I had to go on.

was the waterpump changed in 100K service?