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Discussion Starter · #1 ·
Finally got around to tackling the rust on my 04 Mk2.5 Mx-5 Passenger Sill today with a lot of help from my a friend Matt in Northampton who is a welder/fabricator for a local racing team. Of the two sills, this one was the worst but was not showing too bad thanks to the a bit of treatment/underseal a couple of years ago. However I was surprised by how bad the rust was once we got the top skin removed. I'm glad we tackled it today & planning to sort the other side's sill next weekend before the rot sets in. Given the car is now mostly garaged & out of the rain I'm hopeful this repair will last a number of years. I've included a few photos so you can see the job in progress & work involved.

Underseal hides a multitude of sins...

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Spot welds removed & the rust starts to be revealed...

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After a bit more cutting, we find some good metal ;-) and more rust :-(

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Quick check with the repair panel (ebay special)

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More cutting and nearing the end of the rust (hopefully)

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Finished cutting and after a bit of grinding, some decent metal begins to shine through

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Enjoy some lunch whilst the rust treatment goes off

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Primed and ready to go

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Matt spot welded the repair panel in, v neat. He had to fabricate an extra piece to fill the gap not covered by the repair panel

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Welding complete, v tidy job - cheers Matt (you've earned a pint or two for that!)

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That's where we got to today. Weld needs grinding back but its looking like we can get it flush with the panel & then applying stone chip & top coat of paint to blend in with the surrounding area. Hope it gives others an idea of the work involved, let me know if you have any questions or want to know any more about it.
 

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Nice job and welcome to Nutz.
 

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Discussion Starter · #4 ·
Matt has managed to do a bit of grinding this evening...

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Don't think it'll need much (if any) filler, it's looking pretty smooth, shiny & rust free - :goodjob: Matt!

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We will hopefully be painting her up at the weekend & tackling the other side
 

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Discussion Starter · #6 ·
I've had the car around 3 years but it's clearly took me a while to get involved with the Nutz community. It was apparently 'rust free' when I bought it! Will try to share any future projects I get up to with it.
 

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MARK AT TOTAL MX5 REPAIRS
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Nice job. Gary at OAL really makes nice repair panels. he does make larger sized panels for rust that has crept up a bit higher..
 

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I think an OAL repair panel is what we used, see link below:

http://www.ebay.co.uk/itm/NEW-PAIR-MX5-Eunos-Miata-MK2-MK2-5-Rear-Sill-Repair-Panels-Both-Sides-Schweller-/331699251212?fits=Model%3AMX-5&hash=item4d3ad0e80c:m:m5Z-hL1QsZqiXGNbW92-ZTg

We thought the standard size ones would be big enough but it wasn't until you start tackling it that you realise how far the rust had travelled up! We were trying to work out what causes it to rust, is it likely the water drains from the roof have been blocked at some point and the filled up the inside of the sill & inbetween the various panels that make up the sill?

Thankfully my friend Matt is v handy so was quickly able to fabricate a section from the remains of the repair panel we used. The drivers side sill doesn't look so bad so hopefully the standard panel will fit, should be a lot easier now we've had practice!
 

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Discussion Starter · #9 ·
We managed to tackle the driver's side today & as suspected the rust wasn't as bad this side

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After a bit of grinding and sanding, got back to some clean metal

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Then after rust treatment & paint, Matt did his magic again and welded the repair panel in, v tidy

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Car is looking a lot better on both sides. The first few coats of stonechip were blended in on the passenger side today, drivers side will get similar treatment when the primer has dried. Matt then plans to give both sills a top & clear coat of paint up to the edge of the factory stonechip.
 

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We were trying to work out what causes it to rust, is it likely the water drains from the roof have been blocked at some point and the filled up the inside of the sill & inbetween the various panels that make up the sill?
This can be the cause, but water can also get in there by other means. Any water in the cabin can eventually lead to condensation forming in the boot, which in turn can drip onto the wheel arches and trickle into this area. Hood rain rails can leak and allow water to find it's way there too. The small drain holes only serve as exit points for water trapped between the inner sill and outer sill panels, which at the rear are then covered by the outer wing skin with virtually no gap between the outer skin and outer sill panel. Once in between the thinly separated layers of steel where there is no flow of air, the water will take a long time to evaporate allowing rust to develop. It is virtually impossible to ensure decent coverage of this thin cavity when rustproofing and partial filling could even exacerbate the problem creating more voids to trap water. Here's a link to a post and animation by The MX5 Restorer explaining the rear sill construction in excellent detail:
https://www.mx5oc.co.uk/forum/yaf_postst43393_Exploding-diagram-video-of-the-rear-sill-area---Made-by-The-MX5-Restorer.aspx
 

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Discussion Starter · #12 ·
Thanks AndyK for the detailed response, sounds like it's a pitfall of the design. The car is mostly garaged and rarely out in the rain so hoping the repair will last for the rest of its time with me.

Chi Kung - It is mostly Matt's handy work. I'll have a word with him and message you what he thinks
 

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Payday! Aaaand it's gone.....
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Top quality work by Matt! Are the ebay panels thinner than the oem metal?
I had the arch repair panels and when I took them to my dads friend who's a fabricator/classic car restorer he didn't even use them as they were 'cheap crap' if I remember rightly.

He fabricated the sills, and I've not needed any filler on them at all, the real test is if OEM sideskirts go over as they are probably aren't 100 original size.

Sent from my SM-G920F using Tapatalk
 

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MARK AT TOTAL MX5 REPAIRS
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Gary's panels are much thicker then the o/e metal. but as said the rear arch and sill panels that are available on ebay are rather flimsy if you buy cheap ones.
 

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Discussion Starter · #19 ·
Gary's panels are much thicker then the o/e metal. but as said the rear arch and sill panels that are available on ebay are rather flimsy if you buy cheap ones.
We used the OAL panels and as Penarth MX5 parts commented, they were pretty thick panels (from checking the listing, they are manufactured from thicker than standard 18 gauge (1.2mm) steel). Matt commented that with a template, he could make up his own sill repair panels. However, given I'd purchased a pair of panels already, they were fine for the job & gave a decent finish with a bit of fettling by Matt.

Matt also managed to finish the paint on the driver's side of the car last weekend (I was away this week hence slow response).

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Very happy with the finish to both sides - if only the rest of the car's painwork looked as good ;)

Thanks for all the good feedback on the work done. I spoke to Matt and he said if anyone in the Northampton area is interested in getting some similar work completed, feel free to get in touch with him on his email - [email protected]
 
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