I’m looking for technical help or recommendations on: Rust treatment
Hello everyone, this is my first post here so please be patient with me! I have trawled the forums for days now regarding rust treatment and would just like a couple of questions answered.
I bought an NC 2.5 on the weekend and adore it. However it’s a little rusty underneath (praying it’s suface rust) around the suspension parts and a little of the subframe. Wheel arches and sills look okay.
Fortunately the dealership has included a free waxoyl or dinitrol treatment which I’m gonna get on Tuesday.
This is fantastic, but the fact they state it’ll only take ‘an hour or two’ doesn’t fill me with confidence as I’m aware that surface rust will need to be removed, wheels removed etc. and the full works which is what I’ve read is necessary.
What I would like to know is if this level of rust looks like something that’s able to be tackled quickly and without needing to nag the garage to ‘do a proper job’ before I even take it in to them. That would seem rude and perhaps I will just have a chat with them before taking it in to see just what exactly their full process is!
Would you recommend dinitrol or waxoyl in this case?
Again it’s free for me so it’s surely better than nothing. My fear is that they’ll just slap some waxoyl on there without properly removing the rust first and end up sealing in moisture and dooming my lovely new (14 years old) car!
Here are some pics of the underneath. If I had my own ramp I would surely already be under there right now with a wire brush! But I’ll have to stay patient and see what the garage will offer first I guess.
I suppose what I’m really searching for here is reassurance from folks who have been in a similar situation!
Oh by the way - unrelated - I keep hearing the occasional clunk from the rear left suspension (I think). It got MOT’d and passed last week (from the dealership/garage mind you) but wondering if this would be a worn drop link or shock absorber?
Best advice to anyone buying any MX-5, even brand new, particularly if they envisage long ownership is to take it to a reputable specialist for an underside with cavity inspection and get a quote for taking the whole underside back to bare metal and getting the cavities protected.
Yours does not look particularly bad, as you aleady indicated slapping stuff on top will only accelerate the process and personally I’d avoid what your dealer offered even if it’s free, 1 or 2 hours is unlikely to get the job done thoroughly and I am guessing your dealer is neither Mazda or an MX-5 specialist.
Wire brush it yourself, as your first step in engaging with the car. Most of the so-called specialists can’t really stand behind their work. Its not their car after all.
It’s important that the wheel arch covers are removed and the rust is brushed off everywhere before the treatment is applied.
I won’t advise on Dinitrol v. Waxoyl but my 0.02 is that either is fine, as long as you do one of them - and properly at that.
These guys below were good for my MX-5, but it took most of a day not “an hour or two”. Factor in around £450+. Your dealer may have a preferred supplier, maybe speak to them and offer to pay extra for them to do the full job not the quick job.
In my experience, rust jobs are better done yourself or taken to a sad idiot like me who actually cares about doing a stellar job. To do it properly, all rust must be abraded off completely, accept no chemical treatments over proper application of elbow grease. Get a wire brush grinder wheel, an electric orbital sander, a large and small steel wire brush, some drill wire wheels and plenty of p60/80 grit sandpaper and give it the absolute business. Before any sort of underseal or water-repellent coating, a decent rust/corrosion-proofer must be used. I prefer red oxide but hammerite is acceptable in my books.
Waxoyl and dinitrol, stuff like that, that’s rust PROOFER, not rust TREATMENT as far as I’m aware. They’d be wasting your time if they just slap rust proofer on it, because that would just have to be removed as well when the proper job comes around. As you say, it will only seal in the problem and allow the rust to do its thing without it being as visible. As I understand it, the chemical reaction that causes rust produces water molecules, so merely proofing rust from further water ingress is not enough, as the rusting process creates more conditions for more rust!
Also, I’ve done tonnes of rust treating and proofing and welding etc and I’ve never used a ramp. A decent jack and sturdy axle stands do the job just fine.
Thanks everyone for your helpful responses. I dropped in to the mechanic today who did confirm that it’s a quick ‘once over’ with the lanoguard or waxoyl which was sadly not what I wished to hear. Says it’s a 45-min job and costs £120. They don’t remove wheel arches and I think that they also don’t remove wheels (can’t 100% remember).
Anyway, I don’t mind them slapping some free lanoguard on there for me provided that the rust is first treated, so that’s been my new task at hand!
Picked up some metal brushes, one for my drill, sandpaper and a bottle of rust converter. Here is some of my progress today. The very orange looking parts (mainly the suspension arm/RARB?) are where I’ve gone at it with the brushes and then slapped on some rust converter.
Also, should I use this treatment on my exhaust box? Would it make it look black? Is that undesirable?
Before doing any treatment I would recommend having the wheels off it and using a wheel brush and some wheel cleaner on everything in there followed by a good jet wash. Let everything dry and you can see what’s what. I did on mine and was pleasantly surprised at how it came out. Then you can be sure what is grime, mud, grease, oil and rust. As you can see in the pics, everything was caked, looking crusty and rusty but after a once over the condition wasn’t as bad as I feared. Not saying you’ll be as lucky, but I’d have a go first to see what you’re working with .
I wouldn’t get too obsessed with this. Yes, ideally get rid of all the rust you can get to but don’t forget some is, in practise, inaccessible. You may be able to get a lot of stuff back to bare metal and get a good basis for keeping rust at bay ( with annual top-ups if we are being realistic).
Just look at a typical sub-frame. It gets very rusty as it’s right it the center of all the water and salt spray. It’s typically two pieces of stamped steel welded together and has lots of holes that allow water in and out. Realistically you will not get your tools into those cavities and your best bet is likes of Waxoil etc that at least form a barrier to even more rust attacking your Precious.
Edit: Waxoil et all all claim to displace any moisture present. That probably correct but partial.
Get as much treated as possible (scraped off, rust converter applied) pre the under treatment. I’d go with the Lanogaurd treatment, this needs to be topped up annually anyway. You’ll be able to tell where the rust is as it’s clear treatment, just systematically work your way around the car afterwards at your leisure with your own treatment. I recommend Dintrol, pay particular attention to rear wheel arches and under the car on the rear sills portion near the wheel arch. Getting it ground down to bare metal and slapping plenty of treatment on there.
Thanks again for the great tips everyone, it’s really helpful!
Had another quick bash at it this morning and worked on rust converter. Compared to my previous updates and Imgur links, you can already see what a difference it’s made!
I’ll try and get it jacked up and have another couple runs at it before I do take them up on the lanoguard. I’d like to take the wheel arches off (and wheels but I don’t have a torque wrench to do them back up) but unsure how.
I’ll keep updating as I go!
Oh and as someone just mentioned the subframe - regretfully this odd crossbar looking section kinda in the middle of the chassis was really REALLY flaky. Any advice? Perhaps I’ll take it to my most trusted garage and ask the mechanic to take a glance over to reassure (or dissuade!) me.
Thanks Beryl. Helpful stuff. Is this part of the subframe here, next to the catalytic converter? I’ve painted it with rust converter but alarmingly it was very rust damaged and flaky. https://i.imgur.com/dZfIxVD.jpeg
No. That’s a reinforcing strut. It’s actually, in its construction, like the subframe. It comes off with just three bolts each side. I did mine recently. They are a good item to cut your teeth on vis a vis rusty bits.
Just to a wider audience, I did think of using expanding foam to keep moisture out of these hollow structures. Just tape off all the holes except one to get a good fill.
Have I missed something?
Astonishingly bad idea. The expanding foam will absorb moisture.
A few tyears ago, it was all the fashion to fill the sills with foam to stiffen the car. It was a disaster. The foam absorbs moisture, but also cracks as the car flexes. Even closed cell, hydrophobic foam will trap water against a metal surface.
Once you do it, you can’t undo it. Also, it might stop welding in that area once the foam rots out the part.
If the bracing bars are rotted through or very flaky you can replace the pair for about 60 pounds. Mine had suffered seeing as they’re laid pretty much flat at the lowest point of the car. I opted to replace as by the time I’d bought the products to treat them and the time required, it just made more sense. These were well made with a quality finish and a perfect fit.
Those braces are exposed but also easy to remove, access-wise. They are a good indication of your general underside condition. canary in the coal mine sort of thingy🙂
Mine were rusty but fine. I power brushed the outside and flooded the internal surfaces with inhibitor then Waxoiled. Currently it’s the best a DIYer can do?
In my experience a proper rust treatment is going to take about 2 or 3 days, if done properly. The most important thing is removing the old rust and scale before treatment. Personally I’ve always used the Dintrol system. Getting it done by a proper professional will cost at least £1000 nowadays. I’ve done it myself and it took me several weeks on my back with wire brushes and my Black & Decker with the Dinitrol products costing about £350. To be honest it’s an awful job.
I had a 2009 MC3.5 Roadster for many years. It was immaculate up top but, like most MXs. a different story underneath. Keeping rust at bay was constant.
Wire brush, power wire brush as much as you can possibly get to, then, jenolite all cleaned areas,then waxoyl whatever. Jenolite used by MOD,I’ve used it 40yrs,you will not be disappointed, good luck.
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