Had its MOT a few days ago. Passed, but the guy said that it only scraped through and next year it will need a raft of welding to get through next time.
This surprised me, as I thought that the Mk 3 had resolved the rust problems of the Mk 2.5.
Here is the list of advisories:
subframe corroded but not seriously weakened rear (very corroded all over)
- subframe corroded but not seriously weakened front (very corroded all over)
- suspension arm corroded but not seriously weakened rear (all rear suspension arms very corroded)
- underside of car is very corroded around behind fuel tank
- subframe mounting prescribed area is corroded but not considered excessive rear (all rear mounting points on body corroded)
- offside rear (floor very corroded)
- underside of car very corroded
The inspector also said he could not inspect the outer sills due to cover sills being fitted.
To have all this report makes it sound like the car is just a heap of rust and cannot be economically repaired - extensive corrosion of subframe is a killer, isn’t it ?
Does anyone have a view on this please, whether the cost of repair is £100s or £1000s, whether attempting to repair would be foolish because the rust has spread everywhere like cancer.
From the outset of owning the car I did notice that there didn’t seem any undersealing but as I say I thought it was only Mk 2.5 that had big rust problems.
Yes the NC does rust and in some cases very badly. there should have been something about this rust on previous MOT’S. Take it to a garage and put it up on a ramp and see how bad it is. The subframes may just need a wire brush and painting. Realistically, about £500 needs to be spent to treat the rust to stop it becoming terminal. It may just be more expedient to run it for a year and then scrap it without spending any more money on it.
Lots of previous posts on MK3 rust which is specifically underbody/suspension related. Some ‘X’ rated videos from MX5Restorer on the subject where you can clearly see how bad things can get.
Your car has just passed an MOT! This tells me that the situation should be recoverable.
Take the hints and get restorative/preventative work done.
Maybe not as serious as it sounds. Subframe and rear suspension arms are prone to surface rust that needs attention, usually wire brush and rust killer etc, however, take nothing for granted as elements of the subframe and also fitting areas can rot through. Rear sills at the front of the rear wheel arch and the return panels inside the wheel arch go badly. Really need to take off the arch liners and sill covers to see what lurks beneath, but be ready for some nasty surprises. I have seen one or two that are eaten alive in this area and been scrapped because of it.
No real way to know without getting underneath and removing a few covers. If, like mine, rust is mainly surface on subframes etc, it is quite easily dealt with. Sills and wheel arches need a welders attention unfortunately.
Thankfully my front end was clean so I can’t really add anything here.
I can send some pics if you need to see where problems lurk.
These frames are reasonably sturdy bits of kit to be fair. If it was that bad, including the floor pan bits mentioned, it would not have passed this year. I bought Bilt Hamber materials (rust converter and sealer) and attacked my underside on axle stands, a bit at a time. Clean off, wire brush by hand or with a drill attachment. Then treated and protected, zero issues at MOT time. They do rust, they can look awful at first glance but sounds more superficial than terminal. Get it treated and stop worrying! Its not just a case of trying to move it on now, it’s recorded and this will put buyers off completely. Get it done and hopefully pass next year with no further advisories, then if you decide to move on, it will have a better chance as the advisories will have been dealt with. They all rust to some extent, some worse than others unfortunately.
As an NC owner I am surprised by the rust on mine but I put most of it down to the car not be used. Its clear on my car is it has been sat (06 model with less than 60k) for most of its life. If its not garaged (or in a damp garage) water/moisture can get everywhere. If the car is parked up in a corner near a wall one side may not dry out in the winter, water can run off trees etc and get into places in quantities is shoudl and so on.
They key thing is to do preventative work but also to save these cars. 20 years ago everyone was scrapping Fast Ford due to minor rust. Now people are spending a fortune on rotten shells. The Fast Fords are over priced and it cant be all about the money but all MX5s must live on despite these challenges.
Had similar disccusion with my friendly MOT garage on how my car prior to me owning had passed for years with out mention of rust then the first year I bought it failed MOT on corroded rear part can’t remember the exact phrase.
Anyway MOT garages don’t have to report rust due to it been an impossible time scale for when failure will happen.They generally discuss with customer to give them an idea of future problems…makes sense really, last thing you want to do is change all the parts because of surface rust that will probably still last for years.
Off topic posts removed, and archived; please stick to the questions asked, if possible.
While reports are surfacing of rust on the NC, there isn’t enough for reasonable estimates to be formed of unseen cars, unlike NBs and NAs, which are so common for rot, its fairly easy to give reasonable estimates.
The only anecdote I can offer is from Thrussington Garage (MX5 specialist), who noted that when rusting occurs on the NC, it is “everywhere” (on the underside). Pretty much all the repairs have to use bespoke parts. On the upside, fabbing the bits is easy, and because its the underside, you don’t need to worry about the cost of paintwork, which is the biggest element of NA/NB repairs. He’s done a few, so I guess the cost wasn’t bankrupting owners.
