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Just wondering how long on average an NA8 should take to get up to operating temperature (on the gauge)?

Mine seems to take close to 10 mins of driving before the heater puts out any noticeable heat, something that's made for some painful mornings lately when starting work at 5am!

I think I'll change the thermostat and see if that helps, unless 5-10 mins is normal?

My coolant temp takes a few minutes, then oil takes a good 5 minutes longer. I'll take a look next time I start the car to redefine 'a few minutes' a bit more accurately.

4-5 kms of driving or about 5 mins, This is with a 52mm radiator and 15 degrees is about as cold as it gets here.

My car is up to it's operating temperature in the time it takes me to drive out from the 3rd level underground carapark at work, so approximately 5 minutes.

I had a stuck thermostat a while back, and the car would take around 10 to 15 minutes to warm up properly, and the temperature gauge would drop to cold on long hill descents.

I have a large aluminium PWR radiator.

It wouldn't matter if you had a radiator out of a Mack truck. The thermostat is meant to stay shut and not let water through to the radiator until the engine is up to normal temps. 10 minutes is too long. Either the thermostat is opening too early or not shutting properly or your temp gauge is reading wrong. I'd take the thermostat out and, if it looks OK, test it by bringing to boil in a saucepan with a thermometer in it. It should start to open in the 80s. If it looks crusty or is not fully shut when cold or fails the saucepan test then replace it.

Thanks guys, I'll pop the thermo out and have a look at it. Might just replace it anyway while I've got it all apart.

If you are replacing the thermostat, test the new one as described above before fitting. It's not uncommon to get a dud one from the box.

if you want it to heat up quicker do a coolant re route.

Does anyone know, offhand, whether we can use the Ford Laser or Mazda 323 thermostat?

Assuming your talking about the bp or b6 engine versions, probably.

Check what their temps are, all model mx5 actually changed the thermostat slightly. Have a look on the Mahura website for photos and temperatures.

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Temperature conditions can make a big difference, in WINTER i was unsure if the fan was working lol. In Summer it kicked in after 5 minutes.

My NB took about 4-5 mins before the thermostat would open