Finally the floor is up in my Mercedes Sprinter Conversion and that leads to the inevitable question, how best to fill the holes left over from ripping up the floor.
Pardon the phrasing here but there’s many types of holes that need filling. First up are the ones left over by the self tapping screws. These are typically around 16mm – 50 mm but thankfully the same diameter. No matter how deep the hole with width is the same which is M4.8 or 4.8mm.
Before you fill the tank, the whole treatment is important, and this is where the devil is in the details. If there are any signs of rust, this has to be treated; otherwise, the problem will get worse. If you have a Mercedes, this is especially the case.
Steeltip Wire brush
Providing you have a drill, by far the most effective way to remove rust is a Steel Wire Cup Brush (Amazon). There is very little pressure required to remove rust; just let the weight of the drill and the wire cup brush rest on the rusted surface. Go around the hole in a circular motion, and all you are trying to do is just remove any rust (brown stuff) on the exposed metal. Try to take off as little as you can; you aren’t aiming to get things shiny, shiny, just get the rusty stuff off.
Rust Treatment.
Once the exposed area is nice and clean, the next step is to prevent further rusting. Metal meets air + water is going to equal rust. Hammerite – Kurust is the stuff you need.
Of course you’ll need some brushes to go with this and if you can try and find the u bend type as it’s always good to to the underside of any holes if you can (more about going underneath).
When I first applied this, it looked just like white water with no adhesive qualities at all. I thought this was an off batch, but nope, this is how it’s meant to be. Generously cover any exposed spot, and then the magic happens, turning the white from blue to black. Then you know it’s worked. 15 minutes is all it takes when not freezing cold like here in the uk at the time of writing, and then after 3 hours, it’s ready for a 2nd coat. Don’t skip on this step, as once that floor goes down, hopefully, it won’t be coming up or need to come up.
Even more rust prevention.
So far I’ve listed the steps to clean and treat rust but now’s the time to prevent rust. Basically what is the difference between Kurust and a Hammerite Metal Oxide Paint.
Kurust transforms an active surface into a hard, stable black surface (simplified). It’s similar to general painting, where you use a primer or undercoat.
This is where Hammerite Primer – Red Oxide Metal Primer is the next step. Red oxide metal primer is a rust-resistant topcoat paint and once applied prevents rust from reoccurring. The topcoat takes 6 hours to fully harden, so don’t skimp on the 2nd layer.
Under the van.
Yes it’s a pain in the backside, yes working on a cold concrete floor is never fun but going that extra mile lets you enjoy the years of your van without that rust worry. If you can do all of the above after sealing treating the underside with Wax Oil Rustproofing Aerosol will be a choice you won’t regret and the chefs kiss to prevent rust and water leaking through.
Sealing holes in the floor of your van
Preparation is key and more than likely the above if done properly will take the best part of a day, that not including dual coats which is always recommended. Now for the “fun” part sealing up those holes.
For the smaller holes caused by self tapping screws and up to 5mm in width
For the bigger holes I’ve heard many a suggestion to fill them. One has been to use spray foam, cut off the excess and done. Personally I’d not consider this as it can wear out after time and it’s porous.
Rubber bungs are also on the suggested list and your holes aren’t deformed a good way to go providing you can find the right size.
By far the best way to go is one of the many brands of epoxy putty.
A steel reinforced epoxy putty has many benefits including being resistant to water, oil, and chemicals. Also once hardened, it can be sanded to match the surface level of the van and painted over for a seamless finish. Finally putty like this handles van vibrations. SteelStik is the closest you can get to welding without welding.
To use please wear gloves!. Cut off the amount of putty you need and knead it by hand until it turns a uniform color (usually gray). Press the putty firmly into the hole, ensuring it fills the gap completely. Smooth the surface with your fingers or a tool, and let it cure for about an hour. Once hardened, the repair is durable, waterproof, and ready to be sanded, painted, or left as-is.
Tl;dr Final Workflow for Your Van Floor
Grind back loose rust to bare metal.
Apply rust converter (Kurust) to neutralize any remaining rust.
(Optional) Prime the area with a metal primer for added protection.
Use SteelStik to fill and seal the hole.
Once cured, sand the surface smooth.
Paint the entire area with a rust-resistant paint like Hammerite for extra durability and a clean finish.
