Front chassis rust
Discussion
Hiya,
Our '99 1.8 S has just failed it's MOT on rust to the front chassis rails around where the ARB mounts are. Is this a common thing? Has anyone repaired anything like this before?
Thanks
N
Eta, same as this guy - http://forum.miata.net/vb/showthread.php?t=397790
Our '99 1.8 S has just failed it's MOT on rust to the front chassis rails around where the ARB mounts are. Is this a common thing? Has anyone repaired anything like this before?
Thanks
N
Eta, same as this guy - http://forum.miata.net/vb/showthread.php?t=397790
Edited by buggalugs on Thursday 5th July 15:08
Yeah I would be doing it myself. The MOT man said something about it having layers; if I just cut out the brown bits and weld say 2mm plates in will he have a problem with that?
It's a '99 1.8-S. Pretty shocking for a '99 car to get into this state. Sills need doing too... and a caliper... and a brake hardline... and tyres
But I know what a ball ache it is breaking a car for parts!
It's a '99 1.8-S. Pretty shocking for a '99 car to get into this state. Sills need doing too... and a caliper... and a brake hardline... and tyres
But I know what a ball ache it is breaking a car for parts!
Not sure, it was bought as a track-y project and owes us about £900 as it stands. I foolishly didn't pay much attention to rust when we bought it cause I wasn't too bothered about cosmetics and thought how bad can it be on a '99?? <<< ERROR.
Just been round it with a hammer and think I'm going to weld it, I think we could 'cash out' without too much pain if we put it on ebay with the fail sheet but then another one we buy is going to be on the same road to this state anyway by the sounds of it.
I will post pics of my ugly welding when it's done!
Just been round it with a hammer and think I'm going to weld it, I think we could 'cash out' without too much pain if we put it on ebay with the fail sheet but then another one we buy is going to be on the same road to this state anyway by the sounds of it.
I will post pics of my ugly welding when it's done!
Well the project is progressing at breakneck speed...
Been cutting chunks out of it now it's in the garage -
What you're looking at here is a cross section of the base of the left front chassis rail, I've cut half of it out.
Before I started cutting it looked like I was cutting all the rust out, i.e. I was cutting into clean steel. But you can see there that the sandwich construction is rusting from the inside out, in places there is almost just a tissue of clean steel over a good few mm's of rust. If you scratch it or hit it with a hammer even it would seem fine but there would be no real strength there whatsoever, and in another year or so the rust would be breaking through in more and more places.
Where the metal is good and close together is where the spot welds where, inbetween them the good metal has been swelled apart over time.
From the outside the only slight giveaway that this is happening is a slight swelling on the surface of the metal, it should be flat not have any bumps in it. It doesn't come out well in the pic but looking at the back wall there of the box there's a slight raising of the metal between the spot welds, I feel confident that if I cross sectioned that it would look exactly the same as this
From what I can see the whole area with this sandwich construction is like that so the whole front leg of the car would have to be removed and replaced to fix it properly. It's even going to be difficult just to patch the bits that have holed naturally since the metal is so s
tty to weld to 
I can see a lot of Mk2 and 2.5's being parted out in the next few years!!
Been cutting chunks out of it now it's in the garage -
What you're looking at here is a cross section of the base of the left front chassis rail, I've cut half of it out.
Before I started cutting it looked like I was cutting all the rust out, i.e. I was cutting into clean steel. But you can see there that the sandwich construction is rusting from the inside out, in places there is almost just a tissue of clean steel over a good few mm's of rust. If you scratch it or hit it with a hammer even it would seem fine but there would be no real strength there whatsoever, and in another year or so the rust would be breaking through in more and more places.
Where the metal is good and close together is where the spot welds where, inbetween them the good metal has been swelled apart over time.
From the outside the only slight giveaway that this is happening is a slight swelling on the surface of the metal, it should be flat not have any bumps in it. It doesn't come out well in the pic but looking at the back wall there of the box there's a slight raising of the metal between the spot welds, I feel confident that if I cross sectioned that it would look exactly the same as this
From what I can see the whole area with this sandwich construction is like that so the whole front leg of the car would have to be removed and replaced to fix it properly. It's even going to be difficult just to patch the bits that have holed naturally since the metal is so s
tty to weld to I can see a lot of Mk2 and 2.5's being parted out in the next few years!!
Edited by buggalugs on Monday 8th October 09:38
I read a thread there by a guy with a light blue one, £314+VAT a side for the part wasn't it. That's going to write this car off and then some... this car needs sills too.
It's weird, when I first googled this issue in July there was very little on the web about it, just a couple of chaps in the US. Seems to be becoming a bigger issue over time though.
It's weird, when I first googled this issue in July there was very little on the web about it, just a couple of chaps in the US. Seems to be becoming a bigger issue over time though.
I'm sure someone will rip my arse out for crappy welding but here goes -
I went about as high up again on the other side, and either chamfered back the outer layer or welded from both sides where possible to tie both old layers into the thicker new single layer. I beat the st out of it with a lump hammer and nothing moved so just hope the MOT man likes it!
Other side looks about the same, just finished replacing the rear outer sill on one side, other side needs same, then a few bits and bobs then MOT time. Honestly I'm expecting it to come back in new places in a couple of years so will have to decide to keep patching or break it, I think I'm a bit mad for doing this much TBH but we'll see.
I went about as high up again on the other side, and either chamfered back the outer layer or welded from both sides where possible to tie both old layers into the thicker new single layer. I beat the s
t out of it with a lump hammer and nothing moved so just hope the MOT man likes it!Other side looks about the same, just finished replacing the rear outer sill on one side, other side needs same, then a few bits and bobs then MOT time. Honestly I'm expecting it to come back in new places in a couple of years so will have to decide to keep patching or break it, I think I'm a bit mad for doing this much TBH but we'll see.
I'd say my ability now is a lot better than before I started! 
On the other side of the car I had to go right up to the top to find good metal. It's scary how many must be driving round with no strength at all in those front sections
This car had a month's MOT left on it when we bought it, there's no way all that happened in 11 months...
On the other side of the car I had to go right up to the top to find good metal. It's scary how many must be driving round with no strength at all in those front sections
This car had a month's MOT left on it when we bought it, there's no way all that happened in 11 months...Gassing Station | Mazda MX5/Roadster/Miata | Top of Page | What's New | My Stuff