Rot in sills at rear wheel arches?
Discussion
Looking to get an MX5 and all the models I have looked that date from 1999 to 2004 have the same problem where there appears to be rot. The picture shows where I am talking about. I have heard to versions of why this occurs. One is choked internal water run-off channels and the other is a reaction between different materials used in the construction of the car.
Can anyone help on this?
Can anyone help on this?
It is more down to the hood drainage tubes not being kept clear, or a badly fitted hood/rain rail.but it can also happen if the undersealing as not been done, more so where the wheel arches are tacked welded with the double skin,water can get in between them if not sealed, resulting in tin worm.
Don't be put off , there are some good ones out there.
I have been viewing Mk 1's for a local owner, and i can believe how many rot boxes are out there, and the daft prices some of these owners have been asking for them, some have been that bad, that they need taking off the road.
M-m
Don't be put off , there are some good ones out there.
I have been viewing Mk 1's for a local owner, and i can believe how many rot boxes are out there, and the daft prices some of these owners have been asking for them, some have been that bad, that they need taking off the road.
M-m
Northern Rockape said:
One is choked internal water run-off channels and the other is a reaction between different materials used in the construction of the car.
The ones I've looked at, it seems to be a combination of things. But one thing I noticed, that part which is arrowed in the pic, is the outer surface of a double skinned section, with the inner piece forming an extension of the inner wheelarch. Such narrow sections are notoriously difficult to rust proof, and form moisture traps. The rear wheel arches on most cars are potentially prone to the same problem, as moisture tends to lie right where the two panels meet. However I have to say the MX5 seems more prone than average.At least the sills and wheel arches are visible, another place to look out for is the chassis rails just in front of the front subframe mountings. I viewed a couple which had serious corrosion on both sides.
Personally I thought they seemed a bit below par when it comes to corrosion resistance. This problem with the sills has been heard of on cars barely 6 years old.
Edited by robgee1964 on Sunday 24th July 14:03
Edited by robgee1964 on Sunday 24th July 14:04
On the sill repair the actual welding is indeed not a big job, and its fairly straightforward to cut and shape a piece of sheet steel to let in.
But, to do a proper job you either need to cut the plate to exact size and butt-weld, or joggle the edge of the existing panel, so that the plate ends up flush. Skim with filler as required, stoneguard and paint to match the body colour. This required good body skills and wills bump up the cost a bit.
I saw a few where someone had just welded a plate on then painted the whole sill in matt black, or underseal. Cheap but nasty job.
But, to do a proper job you either need to cut the plate to exact size and butt-weld, or joggle the edge of the existing panel, so that the plate ends up flush. Skim with filler as required, stoneguard and paint to match the body colour. This required good body skills and wills bump up the cost a bit.
I saw a few where someone had just welded a plate on then painted the whole sill in matt black, or underseal. Cheap but nasty job.
the going rate is about £2-300 a side for repair and respraying. Basically the MX5 comes in two versions, those that have had a sill repair and those that need it.
If you buy one that hasn't its probably a case of how many MOTs you can get away with before it needs sorting!
I just had the passenger side on mine done, because the previous owner had basically never unblocked the hood drain tube...the drivers side is in a much better state.
For reference mines an 02 car, so they are obviously a bit prone, apparently the mk1s are a bit more rust proof.
If you buy one that hasn't its probably a case of how many MOTs you can get away with before it needs sorting!
I just had the passenger side on mine done, because the previous owner had basically never unblocked the hood drain tube...the drivers side is in a much better state.
For reference mines an 02 car, so they are obviously a bit prone, apparently the mk1s are a bit more rust proof.
Imports are less likely to have rust due to the fact that they don't use salt on the roads in Japan but most of them have been here 10+ years by now so many are no better than UK cars. It's best just to look at a lot of cars and buy on condition. Don't let high mileage put you off, rust is a much bigger issue. It will cost more to get the sills/arches repaired than it will to replace an engine!
MX-5 Lazza said:
Imports are less likely to have rust due to the fact that they don't use salt on the roads in Japan but most of them have been here 10+ years by now so many are no better than UK cars. It's best just to look at a lot of cars and buy on condition. Don't let high mileage put you off, rust is a much bigger issue. It will cost more to get the sills/arches repaired than it will to replace an engine!
This. 
Also, when looking at imports, ask how long they've been in this country for. Mine came over here in December 2003, which is why it isn't rusty (yet!). Some have been here as long as '96, so wont be any better than uk spec cars. It also obviously depends on if it's been garaged or left outside the whole time.
I have done several of these for clients at The Sports Car Shop recently, and without doubt having a quarter panel spot welded straight to an outer sill with no drains is ulimately the cause of rust. I have just done two 2003 cars, one with minor problems, easily resolved with my own repair section with drains built in,I also soak everything internally with wax until it runs out of the new drains. The other car required HUGE surgery, as the inner sills, diaphragms,inner wheel arches and even floor required repairs, astounding on a 2003 car.
I love these cars, but an owner or buyer has to be careful!
I love these cars, but an owner or buyer has to be careful!
Had the same problem when we bought the wife's. The local Mazda specialist had the car on their ramp, and told me it was fine, but it wasn't.
Ended up having both rears completely replaced and any/all remaining rust killed and then the full underseal redone - so that we knew definitely that he car was perfect.
It's the only way to be certain
Ended up having both rears completely replaced and any/all remaining rust killed and then the full underseal redone - so that we knew definitely that he car was perfect.
It's the only way to be certain
Gassing Station | Mazda MX5/Roadster/Miata | Top of Page | What's New | My Stuff