Coolant Expansion Tank - Worth it?


I’m looking to replace the coolant tank as it’s the original one still and read many horror stories about it cracking.

My question is: do I replace it with another OEM one that costs £50 or do I need to replace it the more expensive aluminum one at £150?

I’m not bothered about the looks more to do with prevention.

Thanks everyone


  1. My model of MX-5 is: NC1 2006 2.0 75k miles

Whilst you may have read horror stories of it cracking, I’ve not heard one single instance on here.
I even asked the question about 18 months ago, and the answer came back negaitve.
To my knowledge, no one else has encountered the problem either.

Considering yours is about 14 years old, if you really wanted to replace it, fit an OEM one safe in the knowledge it will likely last 14 years.



I agree with the above. The alloy tanks are nice for a bit of bling but unless my physics knowledge is sorely lacking are probably radiating much more heat into the engine compartment.
Failures seem to be more common on US forums where the cars generally attain higher mileages and ambient temps are hotter.

I changed mine when I bought the car last year ,was it nesesary I don’t know but it gave me peace of mind .I just swapped it for another OEM one. For the amount we use the car , I figured it should be good for another 10 years or so.

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this is the advice I was looking for, and yes it was the US forums. 50 quid worth for piece of mind.

Thanks everyone

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I changed mine to the Davefab metal tank for two reasons,

  1. Insurance; the old one was ten years old and seemed to me beginning to become brittle (my imagination?)
  2. Appearance; the black Davefab looks more in keeping wth all the other black bits.

    I’ve since removed the shiny label (dental-floss saw on the D/S tape and white spirit to remove the sticky residue).

There are oddities about the Davefab, such as the orientation of the overflow spigot and the angle of the pressure cap. On the plus side it has excellent welding and a sight glass at the correct level.

it looks cool I’m not gona lie. However with the money I would spend on one of these I can buy the expansion tank, the thrmostat, a new water pump, a new belt and 5L FL22 coolant.

It looks cool well done.

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I changed mine, just because i wanted to.

nice strut bar :ok_hand:

Hi Safetymatch,
Is that the I.L.motorsport tank, and if so is it easy to check the level of the coolant ?

Yes it is the IL and no it is not easy to check the level.
Obviously i have to check when cold and look into the tank and if it appears to be 2/3rds full i am happy with it, I keep meaning to make a dipstick of some kind, possibly a wooden lolly pop stick or similar.
That’s the down fall of it.

I wonder if it would be possible to fit a level window ?

IL Motorsport one for me too. I have a clear plastic tube marked at the correct level which I dip into the tank, cover the top with my finger and bring it out. Shows the amount perfectly and I then just drop the fluid back into the tank.

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guys this isn’t a competition :smiley:

Life’s a competition !!!

Did someone mention DaveFab tanks?