I have a later type ND with the metal valve stems and dust caps fitted to the wheels. These are, I think, the type with the tyre pressure sensor built into the valve stems.
I was trying to remove one of the dust caps to find it was more than finger tight. I then used a 9mm socket and small wrench. With only a little bit of forced I got the dust cap to turn only to find out it was not unscrewing but just spinning around. To cut a long story short I ended having to just pull the cap off with mole grips as it was apparent that most of the threads had stripped on the valve stem and the cap was just spinning. The valve cap had split to allow it to come off! On inspection I found that all the other valve caps were very tight but luckily I was able to remove them, again with a wrench, only to find that the threads on the valve stems were quite severely corroded with the tell-tale white powdery deposits typical of aluminium alloy corrosion due to electrochemical action. The car had been sat for over a month since it was last driven and possibly a couple of months since the tyre pressures were checked.
I would therefore advice owners to put a smear of grease on the valve stem threads and regularly check that the caps are only finger tight or replace them with the standard plastic caps.
Finally does anybody know if tyre dealers can replace this type of valve stem or is it a dealer job?
1 Like
I had a similar problem with my 2019 ND and changed the caps to the plastic ones too.
When I bought a matching spare wheel, my local dealer, NortonWay Mazda, fitted the tyre complete with valve incorporating the TPI sensor and all for a very reasonable amount.
2 Likes
Yeh, I will see how I go. The end of the valve stem is pretty chewed up but I can still use a pump and tyre pressure gauge on it. A standard plastic cap would not screw up on the damaged stem so I swapped a metal cap from one of the other wheels which just catches the remaining threads on the damaged valve stem. I have put the plastic cap on the wheel from which the metal cap was borrowed.
1 Like
My 2018 ND2 came with plastic caps. Sounds like someone put metal aftermarket ones on? They more often than not cause issues as the two types of metal used can fuse themselves. As mentioned, if you have these, finger tight only and a good dollop of grease on the threads.
My 2021 MX-5 came with plastic caps too. I changed them to metal caps but kept them just less than finger tight and with a dollop of copper grease.
Every time I wash the car I give each one a little twiddle.
Common problem on many makes of cars when changing to metal valve caps. Solution seems to be keep to original caps or plastic ones after tyre change.
A replacement probably means a whole new TPMS valve. A set of four is about ÂŁ120 from Mazda, and itâs cheaper than buying Schrader branded valves from a third party vendor. Stick to plastic dust caps.
Can you not just buy one?
My dealer fitted and charged for just one for my spare wheel !
1 Like
I noticed this rusty metal tyre valve on a brand new ND back in 24/04/2016 at the Spring Rally
All four much the same.
Never mind the dust caps, they are easy to change.
The valve is the seal. The cap is mearely a dust cap to keep out contaminants that can damage the valve. Even if the thread is corroded or partially stripped a plastic cap can still be fitted and is unlikely to come off. A pack of 20 can be had for 99p including delivery on eBay. Metal caps just arenât worth the risk.
Ta for the heads upâŚchecked mine today but they are all plastic, so hopefully no need to panic Mr. Mainwaring!!
Same problem on my MB, I wrecked one valve and let the main dealer remove the rest which all felt just as corroded on. Plastic caps now rather than the MB logo stainless caps.
This is an interesting thread. Do we all not check our tyre pressures on a regular basis? Once a week, two weeks, surely monthly at the very least. I can not see how corrosion can become so serious in such a short space of time.
Or do most now rely on technology and only remove the cap when the dashboard light comes on?
Perhaps the problem may not be âmetal tyre vale capsâ after all!!
1 Like
Surely if (and I appreciate that itâs a big âifâ) the TPMS technology works correctly, then there should be no need to check tyre pressures manually.
I must admit that I only tend to check pressures when I know Iâm going on a long journey, or if the handling doesnât feel spot on for any reason. And of course Iâll always include tyres in the visual check that the car gets every time I approach it!
1 Like
All tyres gradually lose air, and the TPMS warning wonât tell you if theyâre all 3psi too low, or if there is a difference of 2psi across an axle. Neither are safe, especially on a sports car.
Mmmmmmm, R above has a highlighted why we should be perhaps more vigilant. Another reason is that ambient temperature has a big impact on pressure, what was good on that cold day when you set the pressures may not be good on a day when we hit 27c.
All metal caps need grease.
