In 2017 I bought a 2010 Mazda mx5 NC cabriolet with 75K miles on the clock, she was by no means perfect but essentially appeared to be sound.
Over the next couple of years I put right various issues which arose after purchase and after the 2020 MOT the examiner commented on the rust he had observed on her undercarriage while going about his business, which got me thinking about what I was going to do about it.
At some time in her life she had been resprayed but her collars and cuffs don’t match, the engine bay along with inner sills, outer door surrounds and inner boot lid area were not included and after finding a piece of broken plastic grill on the inside of a front valance I’m guessing she may have been front ended at some point and hence maybe the respray.
So what to do?
I thought about a professional underbody seal using the likes of Dinitrol and read numerous comments from people not happy with the results due to careless work and then when considering a cost of around £500 or so, was it worth the risk of having no control over the work and spending a considerable amount on a less than perfect car?
Had she been a Prima Donna with half the amount of miles I might have thought it a wise investment but I just couldn’t bring myself to seriously consider it, so went off on a quest to determine what DIY solution would suit.
Lanoguard won the day, there are no chemicals. £71.94 (inc shipping), kit includes 600ml grease, 2lt spray and the spray head assembly.
The manufactures advise “minimal prep” and 20 minutes job done, I don’t think so!
It all depends on the amount of rust, if the vehicle is relatively new with only surface corrosion then yes virtually no prep and you could be done in 20 minutes or so but with me and my 11 year old Mazda it was a different story.
I started by jacking and putting an axel stand at front offside, removing the wheel, completing the work, putting the wheel back then moving on to the rear offside then onto the near side.
Each corner took at least 2 hours to scrape back the rust, another 10 minutes or so greasing nuts, bolts, seams and vulnerable areas then just a couple of minutes with the Lanoguard spray.
Then I moved on to the underside, not really a lot to do there fortunately but I have to say I am really happy with the results, time will tell so took a number of photos to compare when I next come to top up next year which should hopefully be a doddle and will only take 20 minutes (we will see)!
I didn’t bother about rust treatment, the car is a summer runabout and is covered and under cover in winter with plenty of ventilation so didn’t see the need.
The only issue I had was that the spray head stopped spraying after a long session, it was down to a blocked filter at the end of the pipe in the container, easy sorted, pull off, run under warm water, clean off, wouldn’t recommend leaving the filter off as the spray nozzle would then likely block and be more difficult to clear.
Another tip would be to put the grease container in some warm water before use, makes it easier to remove and brush on.
Here are several pics showing before (after cleaning), during (after grease & spray) and after (24hrs later) -
