Now I have a problem...

I've finished refurbishing the bushings on the rear suspension of my '99 Miata and I started removing the front suspension to do the same to it.Then I noticed a rusty spot right where the sway bar supports bolt to the front frame horns of the unibody. I gave the area a whack with my chipping hammer and it went right through. There's an area about ten inches long of rot on both sides of the car. Now, I'm debating whether to try and fix it by welding in a patch or abandon ship and scrap it. Not a good day.

Grind it down, rust primer, weld metal over it, done.

Fix it

The "floor' of the chassis horn doesn't look too bad, but I'll bet there's far more grot than meets the eye. The whole section is actually a sandwich of two layers of sheet metal with some sort of paper/fiber core. Bet that junk wicks the water really well and hides it everywhere.I think I'll go ahead and cut out the bad section on one side of the car and see if I think I can weld in a "good enough" repair panel. That can wait until tomorrow, I've had enough for today.

I've heard the NBs are terrible for that. I'm not sure what the solution is.

Joey

Joel, the answer is "Buy a better one", but the SWMBO thinks I have too many vehicles now, so that will have to wait. If I can patch it well enough to get a couple of more years out of it I can use the time to look for a nice one and sell off something else.

And a closer inspection of the driver's side chassis horn reveals it's much, much worse than the passenger side. My day just keeps getting "betterer and betterer" as I used to tell my mum.

Pics are required.

I feel your pain. I have the same problem with my 2000 expedition. There is significant rust in the rear of the truck (not in the frame) that will in a couple of years be the end of it. To fix it correctly I would probably have to separate the body from the frame. About the only thing I can think to do is take my sand blaster and go nuts under the truck and then follow it up with some POR and then primer and paint and under coat. I fear that this will only slow it down.

I don't have pictures of my car yet, but it's as bad as the one in this thread's first page.
http://www.mx5oc.co.uk/forum/forums/t/46836.aspx?PageIndex=1

Exocet?

DeadSkunk wrote: I don't have pictures of my car yet, but it's as bad as the one in this thread's first page. http://www.mx5oc.co.uk/forum/forums/t/46836.aspx?PageIndex=1

WT F'n F. Arent these modern cars?!

Oh my god, how come I'm just now finding out about this? I daily drive an NB2, this is bloody terrifying. Definitely checking my car when I get back home. I guess the metal sandwich construction bit them in the ass. I don't even know how to prevent this, and it's showing up on low mileage garage-kept cars!

On the other hand, it could lead to a whole new world of VVT/6MT/LSD donors for Exocets...

Meh, just fix it. If it's that common a problem, you'll just have to deal with it no matter what.

Warren v wrote: On the other hand, it could lead to a whole new world of VVT/6MT/LSD donors for Exocets...

Or buying up cheap cars that need a simple rust repair.

In reply to Warren v:

You can't even see the problem area until you remove the plastic undertray and the plastic shields in both wheel wells. It's not hard to do, I just never did it until yesterday so I could get the bolts out of the upper A-arms.
The front of these box sections are open to water ingress. Mine's bad because it's been driven every winter from new, but there are cars with the issue that are newer than mine and haven't been driven in salt. Once water gets into that sandwich it's just a matter of time.

Here's my conundrum .....the repair sections are about $460 each to replace the rails from the spring perches forward, assuming the rot doesn't go any further back. The car would need to be stripped from the firewall forward to replace them (lots of work). I've never done frame work like this before. Those rotten sections are your crumple zone in a crash. Patches will interfere with the crumple zone. Leaving it as is means my car has the structural integrity of a sleeve of soda crackers.
Part of me wants to strip it and attempt to install new frame legs for a challenge, but I'll be plenty pissed if I screw it up and waste another $1000 in parts. Although, the thing to do would be buy one side and see how it goes before committing to the second side.
The smart/safe thing to do is walk away from it and buy another car , but my Scottish ancestry is coming into play.

BobOfTheFuture wrote:

DeadSkunk wrote: I don't have pictures of my car yet, but it's as bad as the one in this thread's first page. http://www.mx5oc.co.uk/forum/forums/t/46836.aspx?PageIndex=1

WT F'n F. Arent these modern cars?!

My question exactly. I had no idea they had these rust traps in front of them. Mazda doesn't seem to have figured out rust like Toyota and Honda have.

@DeadSkunk: It sounds like you have all the data you need, you just need to decide if it's worth it to you. I would probably attempt the repair, myself, but like you said if it doesn't work out it will be really frustrating.

Since I have not done much work on a Miata take this with a grain of salt. How bad could it be to fix? Cut out the bad areas. Make template with cardboard (including bends) flatten out card board and cut sheet metal (or have sheet metal cut and bent) test fit / grind to fit etc. Grind back all the other bad stuff and apply zink rich paint / primer grind edges again and V for good weld penetration. Weld in new piece of metal grind prime and paint. Yes it will kill a weekend but the job really is not all that bad. At least there appears to be access. The spot that is rusting in my truck I can see but is above the frame rail behind the rear axle.

Look at it this way it gives you an excuse to go and purchase some new tools.

Find a clean NA chassis and swap over the NB good ness?

Kenny_McCormic wrote: Grind it down, rust primer, weld metal over it, done.

That is pretty serious looking... Cut, repair and shoot por15 down the length of the framerail...

dculberson wrote: My question exactly. I had no idea they had these rust traps in front of them. Mazda doesn't seem to have figured out rust like Toyota and Honda have.

Toyota's still got a pretty good grasp on how to make cars rust. The truck frames are made of multiple layers of thin steel, which is just begging to rust out. And I don't know how many '00-era Corollas I've seen where the windshield was only held in by gravity and luck. Nothing left at the top to hold it in.

The driver's side rail is so bad that I would have to cut it completely off someplace between the shock mount and the firewall. The upper surface might be salvageable, but I'm doubtful.There is no patching it as it's just a pile of rust held together by some paint and undercoat on the sides and bottom. The passenger side might be possible with an l-shaped patch to the outer and lower surfaces. I'll ponder my options for a day or two and then probably start ripping it apart to get a good look and working room. Maybe I just need to find a suitable car to swap the entire drive train into, like an MGB-GT, or maybe a Chevette.

Ohhhh I like the Chevette Idea.

dean1484 wrote: Ohhhh I like the Chevette Idea.

Yep, can't go wrong with a Chevette!!!

Can't believe I actually just typed that, but the more I think about it, the cooler the idea becomes!!!