- My model of MX-5 is: 2011 1.8 SE__
- I’m based near: Surrey__
- I’m looking for technical help or recommendations on: Underbody sealing__
Ok so even on a Mk3.5 I gather that you probably still ought to underseal even though these cars are better on the rust front than the ones that came before them.
I’ve been quoted £425 for a professional Waxoyl job which would involve removing the arch covers and filling in the holes etc. from an outfit that does MX5s all day long.
Is there a consensus opinion on what product to use or is it all very subjective? My car’s underside has some surface rust but nothing on the drain holes, under the boot liner or the sills (top and bottom). So it’s just ‘standard’ surface rust from a garaged car. But I’d like to be able to drive it in the winter too.
Any views welcome!
Thanks
ps I’m not inviting a debate on whether to do it myself versus delegate the job, I simply have no time. And I want a proper invoice to add to the ‘bundle’ for any future buyer.
Bilt Hamber and Dinitrol are the more modern equivalents. Better at getting into crevices, better at converting odd bits of rust, and less messy. Key is a decent inspection and sorting to major rust issues first, not just covering them up. Waxyol is better than nothing, but I’d much rather use the other products as they are just more effective. Since the majority of the cost is labour it won’t add too much -but a decent inspection, resolution of issues and removal of as much surface rust as possible is still essential first.
MX5 Restorers in Pevensey (near Brighton) did my NC with Dinitrol last year. They are one of the very best in the country, but if you want to use them, book in quickly as I believe they are (rightly) booked ahead for several months.
PS They do a free 19-point inspection.
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Ok thanks both, interesting to hear.
Leftfield question - do Mazda main dealers themselves do rust clean-up and sealing? If so, anyone have any idea of pricing?
To be honest, I would prefer a specialist who do rust proofing all day long. They know where the tin worm hibernates better than anyone else.
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Hi, I have a 2011 3.75 bought two years ago with 30,000 miles on it. Looked to me like it had been garaged for it’s life. Spent £550 getting it protected underneath. Visited the garage part way through the job to drop off some bits and they had taken an incredible amount off the underside to get into every nook and cranny. Had to take the front bumper of recently to replace the grille and found they’d done an excellent job of every surface which I exposed during the job. I bought the car with every intention of driving it in Scotland in the winter and am more than happy to do so after getting it suitably protected.
Also have decent tyres for the winter, Rainsport 5 Uniroyals in my case. Also make sure all the areas likely to leak like the grommets in front of the windscreen have been done. Definitely an all weather, all season car for me.
General point for anyone reading this thread. No matter how well any undersealing is done, you WILL need to inspect it every so often (I can’t supply any recommendation) and redo any places that have chipped.
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I had two imports; one never extra rust proofed, and the other dinitroled when it hit the UK. After about the same amount of time in the UK, both rusted out in the same places.
And the dinitroled car; 10 years after treatment, the stuff was still sodding wet when I had to plunge into the door to retrieve a broken spring on a lock (inside the doors was liberally coated).
So what’s the lesson there - rustproofing makes little difference anyway so save yourself the time and money? Or that Dinitrol is not very good?
+1
Mx5 Restorer did mine 6 years ago and very pleased with what they did, and a number of other jobs since.
drop the subframes , recondition all the parts again , and while the subframes are down , scrape off and reapply suitable rust prevention. stick it all back together and it should last another 10 years
Probably that Dinitrol doesn’t work if applied straight over rust.
I did this on my previous NC on parts of the suspension, I was reapplying it 12 months later as rust was poking through. In short prep is key, grind away the rust to bare metal and use a rust converter too.
I used Bilt Hamber products upon repainting the chassis and just used the Dinitrol had left to coat parts of the chassis that never had rust in the first place.
It’s all quite an undertaking I can see now. And it’s not cheap for a process that has to be repeated every so often.
My (maybe faulty) thinking is to get it done by a professional outfit that will wash / scrape and then apply the stuff properly (inc. sills and doors), then never drive the car on wet roads or in the rain. And I’ll see where that takes me…anything more than that for a £7k car seems excessive but I’m sure that others will differ.
Thanks for all the input, really helpful.
Thought you might be interested to know - I called TM White & Sons’ official Mazda bodyshop in Byfleet and they will do welding etc. to fix rusted Mazdas but it seems not preventative work. There’s probably a business reason behind that around how to guarantee such preventative work etc. which I’m sure they’ve thought through.
The problem with underseals is they cover everything up… so if you have rust creeping in for whatever reason you cant see it until the rust is very advanced. I personally use things like miparox or por 15 that create an enamel like coating. Miparox is like a clear tough rust converting lacquer and is popular within the trade
Ok so I went for a Waxoyl treatment in the end. My car was in good condition but the guy said it was still a good idea to do this and now I can drive in the wet (though I probably won’t!). One interesting point - and don’t shoot the messenger - was he said that untreated MX5s that have lived in Scotland are invariably a rust disaster due to the heavy salting of the road. I’m sure everyone on this forum already knows that. I’d probably extend it to any untreated MX5 driven in the rain or snow anywhere in the British Isles. Oh and final parting point - apparently even the MkIVs should really be treated too. I find that extraordinary but there we are. Thanks for all the input.
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Great stuff and pleased to hear you’ve had someone take a good look underneath and give you some confidence that the car is not unusually rotten!
I had a comment a while back from a local bodyshop that does this kind of thing that I found interesting. Being that the left (kerb side) arches typically go before the driver side. More salt and dirt gathers and puddles in the road and flicks up into the arches on this side (dirt that holds water and moisture in the arches/sills area). I can see the logic in that!
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Yes and you tend to get more scratches on the nearside as the car passes hedges and bushes etc.
Just at the new Mazda dealer in Bookham, Surrey and they had a J-reg Eunos in black with biscuit brown leather up on the ramp - no rust! Must have been treated…
Final parting words from the very helpful parts guy there:
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If you have a tidy MX5 keep hold of it, they are starting to appreciate
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Do the underseal / rust treatment to all of them. Even the new ones need it.
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Take care driving in the wet - the back ends break out, even the new ones!
The big big misconception about de-rusting , treating and undersealing and cavity waxing is that it is the ultimate cure to stopping corrosion , its not, its not just about the weather and salt but also natural condensation in side and out in everything, the treatment is about controlling it, every 12 months, lets say service time, it needs to be checked, “IF” there is a sign in any patches of concern for many reasons from the pounding, you just simply re sort that patch, and check the cavity wax every 2 years to top up.
See it this way, that nice colour your roadster as that gets well over polished only, is just basically a coating of thin plastic over bare metal to look nice and stop it rusting, so if it gets a stone chip or a scratch , whats going to happen to that bare metal with no protection then?, its just the same underneath only it gets a much bigger pounding from a lot of cr*p etc etc, but as most see it , or don’t, its out of sight, out of mind, she looks great at the top with a wax to protect the paint or now the clear coat.
Richard, not everyone out here are slap dash merchants and just “cover everything” there are a lot that know their stuff and what is the correct thing that needs doing.
M-m
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That’s a great explanation of the whole undersealing debate👍.