Considering how common the rear sills rust problem seems to be, surely this must be considered a proper design fault for the MX5?
My car appears to be on its second set of sills, and now they mut be repaired again. On a car 8 years old
Finishingline has quoted £711, ouch!
Shouldn’t the club sponsor some research into this problem? Apparently most other cars in the country does Not suffer from this (certainly not my 14 year old BMW) so could the MX5 design be compared with other cars to figure out what exactly the problem actually is and then a solution could be retrofitted. Whether through improved design on the next set of sills that gets installed, or by retrofitting whatever draining holes, plugs, inspection hatches, plastic covers, foam filling, hair dryer i.e. Whatever it takes to Cure this scourge on our lovely cars!
Or is this the price we pay for having so much fun i.e. like an STD.
If the £711 covers both sides then it is probably in the right area depending on the extent of the damage and the repair method, from what I have see £350 - £450 per side is typical for a repairs to replace rear wheel arch and sill. If the sill is going then there may well be wheel arch involvement as well.
As for the cause this is well documented. The soft top drains in to a catchment tray under the carpet in the rear deck on either side which then drains down pipes which exit under the car. If the pipe gets blocked by leaves, moss or other debris from the roof the water cannot drain away and overflows the tray to go over the wheel arch and in to the sill whch thens rots from the inside. When I bought my car I found a squash ball sat neatly on the top of one drain blocking it completely and the carpet fasteners in the back are a perfect fit! Inspect the drainage holes regularly for blockages and the worst of the problems should be prevented.
There are a number of threads on the Forum covering the topic so have a look in the FAQ’s or try a search.
£700 doesn’t get you a 100% foolproof reapir; it gets you a patch on a wing, albeit very good. The only fully effective repair is a complete rear wing replacement.
My view is, looking at rot damage, that the major cause is the ingress of salty water through a failure in the outer wing/inner wing wheel arch seam. Water per se is not the cause of the rust; thats why Mazda includes a couple of drainage slits in the sill itself. Dirty water does cause the rapid formation of rot (formation of iron hydroxide), and generally, rain water is much cleaner than water thrown off the road.
The guy who undersealed my car, gets a lot of business from brand new car owners (of various makes) who want their cars to really last. Not a bad idea, if you can afford a new (or nearly new) car, to have that extra protection applied.
The problem also stems from the fact Mazda didn’t galvanise the rear of the sills or the rear wings - unlike the rest of the car. This fact is actually displayed in my 2000 MX5 brochure.
It doesn’t just affect MX5s either. I’ve seen 323s and Demios on early 00s plates with rusty rear arches. Pretty poor on a ‘modern’ vehicle IMO.
I’m guessing it was maybe cost cutting on Ford’s part?
Interestingly enough my in laws once had a 92K 626 as a runabout and that had no rust at all at 10 years old. The paint finish was also superb.
This certainly sounds like the core of the problem. What an awful decision they made!
On the North Thames tech day we checked that the tubes were clear, and the previous owner also insisted on being religious about this. Indeed, the drain area of the top seems remarkably clean anyway. I also checked the sill drains on the tech day and they also seemed clear. Basically it comes down to a Lousy construction!
So presumably any replacement sills are Not galvanised, is that an option at all?
Otherwise, is there any other way of protecting these areas with similar effectiveness?
Here are some pictures of the mess, I still cannot believe the state of the sills on an 8 year old car, having already been repaired before (click the picture for a Photobucket gallery):
Users of a sensitive disposition may want to look away now…
Please show me this? i have never known of a galvanised Mx/roadster?,and never seen or heard of one?they would not rust, you would not be able to weld them for sure, with the nice input from ford they turned them all into cheese.
And everything melts and snaps just by looking at them.
Please show me this? i have never known of a galvanised Mx/roadster?,and never seen or heard of one?they would not rust, you would not be able to weld them for sure"
See below :
Amazingly the bootlid is galvanized - didn’t stop them rusting.
Really a crazy idea. My old Porsche from 1983 was hot zinc galvanised and it worked fantastically, although it also needs to be well undersealed on top of the metal.
These days most cars are well rust-proofed and I don’t think it was Ford’s influence on Mazda, as Fords are pretty much rock-solid being designed for Northern European climates/roads.
Spraying some waxoyl or dinitrol under the wing is probably a good idea - even on a new car. Plus checking for tiny stone chips on any painted surface and covering them up. A little extra lacquer sprayed on the paint surfaces that face the wheels is something that I’ve done on our new Hyundai i10, because they are bound to get stones flung at them.
…and yet all the Pumas are rusty. I know several people who only drive Pumas - they buy one, drive it until it rusts, then buy another. Stocks of rust free Pumas are running out.
There seems to be more to the rust cause than blocked hood drain tubes or blocked drain holes in the lower sill flange. These can be clear and still the rust appears. What people refer to as the rear end of the sill is actually the bottom of the rear wing, which covers the sill proper, tucks under it and abuts to the vertical flange which is part of the sill itself (in the Mk1 at least; is the Mk2 the same here?). The tucked-under wing panel has no water exit, so any moisture which accumulates between the sill and the outer wing, up to the level of the round hole in the sill pressing that you only get to see when the bottom of the wing is cut away, has nowhere to go. That moisture can be condensation or it can get in between the inner and outer wheel arch flanges, which are often quite gappy between the spotwelds even before rust has forced them apart further. And of course it can get there if the hood drains are blocked, but that alone is not the cause.
It’s a very poor piece of design. Maybe the solution is to drill drain holes in the lowest, horizontal part of the rear wing about half an inch away from the vertical flange, where there is still a small gap between the outer skin and the sill pressing before they come together by the flange.
Yes my 17 year old eunos is in garage as we speak having a rear wing repair panel fitted ,same old story blocked run off pipe.But at 17 years old cant complain to much as told rest of bodywork ok. Jim.
