Heater problem possibly known issue

  1. My model of MX-5 is: ND
  2. I’m based near: JERSEY
  3. I’m looking for technical help or recommendations on: HEATER

Heater takes a long time to warm up and even then temperature is nowhere as hot as it was a couple on months ago. I have checked coolant and header tank and overflow have liquid. Any ideas please?

Car had its annual service and originally technician denied that there was a problem and that car was not warmed up. However after I insisted that the car was hot was advised that this is a known issue with several modified parts to be replaced and would be ordered,

Anyone heard of this and if so were the parts replaced free>


No… there was a recall on some early ND’s related to an air conditioning pipe, this might be related.

Not read anything during research prior to buying.
If it’s any help mine is blowing hot air within about 1 1/2 miles of a 48hr cold start.
Running temperature (after 4 miles or so) is just under 100c, but not sure how accurate the gauge is.
Sounds like a thermostat issue to me

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Sounds like the thermostat is not opening fully. Not too difficult job to replace and probably wise before we get any hot weather. (Assuming we will be allowed to get out and drive this summer!)


Thanks all, most helpful.

Temp gauge shows just under 100 and all pipes seem hot. This has only occurred recently, heater performance has been fine after about ten minutes. Thermostat was not mentioned by the technician but I will report back when car goes in for rectification. Strange that they knew about the issue but failed to stock the necessary parts.

Again, sounds like thermostat

Just under 100*C sounds like normal operating temperature for an ND to me.

Problem restated below and will advise after car fixed. Sorry to summarise but preparing a complaint to Mazda and any comments .

During service I complained that the heater wasn’t working and was told that the engine had not warmed up sufficiently but after insisting and further running it was agreed that the heater was only delivering lukewarm air although the engine was hot.
The mechanic came back to me next day and told me Mazda had issued a notice advising that “customers may complain about degraded heater performance even when the engine is up to normal running temperature” It seems that this is a known issue and the fix involves total evacuation of the heater system and replacing the fluid with a different fluid. Apparently a special Evacuation Tool is needed which the Mazda Agent had to order as they had not come across this problem before although they are now aware of it. Mazda state that will not pay for this once the vehicle is out of warranty although obviously there is some design/manufacturing fault somewhere in the set up. The special replacement fluid will cost around £50 and the labour about £150. Graciously the garage will not charge for the special toot that they have had to get!! Car booked in for rectification in two weeks’ time.

Has anyone else come across this and did they get any contribution from Mazda to rectify the problem? Thanks

the service bulletin is here

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Thanks, much appreciated. I will give it to a friend who understands this sort of technical stuff as I am supremely non tecchie,

There may be a bit of leverage to get Mazda to make a contribution on my low mileage car…

Hm, nothing about special evacuation tools in that bulletin, but a very detailed procedure to check heater coolant in and out temperatures. It appears the heater radiators got clogged because the (factory) coolant (antifreeze) had insufficient anti corrosion additives. The repair requires the heater core to be replaced. Quite worrying. The car is then filled with the Mazda 55% FL22 coolant. Nothing special other than the fact the antifreeze concentration appears to have been increased. The message is don’t top up the colant with plain water and keep the coolant up to strength. A good few hours work there so no wonder they are not keen to do it out of warranty.

Thanks again, your further input is much appreciated.
Not really looking forward to visiting the garage next week!
I have never had cause to top up the coolant as the level has always been satisfactory when checked.
Perhaps the “evacuation” is meant to clear out the heater core rather than replace it.

In any event I will report back.

Evacuation tool may be required for the a/c system if it has to be disconnected to remove or access heater core?
It’s surprising that the bulletin blames insufficient anti corrosion concentration in what is fairly “new” longlife coolant. It doesn’t bode well for those owners of NC models etc who change coolant at the recommended intervals.
How old is the car?

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Coming up to six years, August 2015 with 21,800 miles.

Sorry to be so long getting back but the problem was solved by the Mazda dealer draining and replacing the coolant at a cost of £207.90 (Our GST is 5%)

I complained to Mazda UK that the coolant was demonstrably not fit for purpose and they refunded the bill in full. Hopes this helps if anyone else experiences this problem.

Really sorry I forgot to thank all those who pointed me in the right direction and in particular the Mazda Service notice. Really grateful to have all the knowledgeable input to help ,my claim.