Expansion Tank info please ??

I keep picking up snippets about the expansion tanks on Mk3s splitting with bad results. I have looked to see if I can find a guide on which cars this affects plus how easy or not it is to do and which specific coolant additive is required. 

If anyone can help or point me in the right direction I would be obliged.


My car is a 2008 2.0 Sport. 

Thanks ???

It’s mainly an age related thing . If yours is looking yellow then it’s a good idea to change it.  Given yours is over ten years old I’d change it for peace of mind.  

thanks… Completely agree it would be daft not too…

i was hoping to find a topic maybe with a guide to exactly what I need and how to do the job. 

Thanks ???

Alas, there is a lack of stock in UK right now. 

I’ve been considering the same thing, with my car at eleven years old (and due a change of FL22), although there is stock of the IL aluminium tanks for slightly more money…

Can I wait a month?  It’s OK right now, but should I put in an order anyway?

This is one case where the old phrase “If it’s not broken, then don’t fix it.” comes to mind…  But then there is also peace of mind…


Changing it is simple enough; three hoses to un-clip in total, the one underneath last after having lifted the tank just enough to gain access. 

But for the sake of tidiness, first drain just enough fluid to empty the tank, and do it cold.  I plan to siphon it out rather than climb under the car and wrestle with the radiator, and I’ll have the dealer change the fluid (and properly burp the system) at the next service.

On my previous NC1, I swapped out the header tank for the ILMotorsport one. Looks very nice in the engine bay  The only thing is, there is no sight glass or other level indicator to see the coolant level is correct. As Richard has said, easy to do, two small hose clips at the top and one large one underneath. OEM cap fits straight on. Worth doing at same time as coolant change whether an OEM plastic one or one of the aftermarket alloy ones. Not heard of any splitting in UK, but reports in the states of this happening. Not to say it hasn’t happened here though. I changed mine more for the looks as much as anything TBH.



EDIT: have a read here, MOROSO tank but same principle.



Barrie do you mean no plastic tanks have split here in the UK ? Or am I reading this wrong ? 

I will take a close look at my tank tomorrow and take a pic… I would rather change it just for the peace of mind but it seems I will have to join the waiting list to get one… Not really into bling under the bonnet where it won’t be seen. ???

Thanks Guys !! 

No there are a few reports of UK cars having the problem and the daft temperature guage does not react fast enough to warn you of the problem until the cylinder head is damaged.

The reports are of cars with more than 60,000 miles on the clock.

I sold my Mk3 at 54,000 miles, 10 years old and advised the new owner and even offered to do the job for them as I changed the antifreeze a year early.

It would have only cost them £60 when I was doing the free to them coolant change.

They just ignored my suggestion.

Their money, their choice. Maybe that one will last for a while yet!!!

Thank you guys for the info. Appreciated… I will get a tank on order ???

I’ve sent an Email to MX5 parts to see when stock may be available… Local dealer can get them next day but typically want a ridiculous price.

Unless of course the part from MX5 parts is a non genuine copy. Does anyone know ?


I’m not best friends with them at the moment  but, to be fair to mx5Parts, it does state GENUINE MAZDA and I would have no reason to disbelieve that. Price (when they are in stock) seems very fair too  It’s £100 less than the blingy one too! 



Might be worth double checking the dealers price with another dealer, they do vary considerably between dealers.  Stoneacre in Doncaster are usually quite competitive with MX5 Parts and will give a discount. 

Have the same thing with the local Skoda dealers.  Sheffield dealer a lot more expensive than the Doncaster dealer.