VW T4 Fuel Flap Refurb

Rust is a pretty common find on a VW T4 and quite a common place seems to be the fuel flap. Luckily it’s a pretty easy thing to either replace or repair.

It really comes down to how bad the corrosion is and whether you want to give it a go yourself. You can pick up a second hand one for £15-£50, at the lower price it will be rusty but maybe not as bad as yours. You can buy a new replacement flap for around £50 but this will need painting. Lastly you can repair it yourself, this is what I chose to do. Trying to find a good condition second hand one is probably the best option and will set you back about £40. However I enjoy working on the van and it’s a good place to practice on as somewhere down the line I want to clean up the wheel arches.

As you can see, my fuel flap was in a pretty poor state. It had completely rusted through in one spot. Your flap will probably be in a slightly different condition however hopefully this post will be of use. Obviously I’m not a professional and I don’t claim to be one, this post is for guidance only.

First thing is to make sure you have everything that you will need for the repair. Here is a list of what I used:

  • Power drill with wire brush attachment
  • Assorted sand paper
  • Sanding block
  • Aluminium mesh
  • Body filler P38/P40
  • Zinc primer
  • Basecoat (custom colour match)
  • Clear lacquer
  • Rubbing alcohol
  • Tack cloth

I then proceeded to grind off all of the rust and old filler, making sure I got all of it. I also stripped back all the old paint that surrounded the rust so that the whole front face and sides were back to shiny metal. On the back I only did around the hole so the filler had a better surface to adhere to. I wasn’t repainting the rest of it so I left it as it was.

I’ve heard differing answers on whether you need to prime before filler as well as after. If you know then leave a comment as I’m still not 100% sure. However as you can see below I decided to cover all the exposed metal in zinc primer before the filler. I then sanded the the entire surface with 400grit sandpaper ready for the filler. Make sure the surface is properly cleaned with rubbing alcohol and a tack cloth before applying primer and then again before applying the filler.


Next up was to cover the hole with the aluminium mesh. This is great for spanning larger holes to add strength to the repair. It’s easy to fix to the flap. Just cut it to the size required and then wedge it between the second skin on the back of the flap. The mesh should sit in there pretty snug so it stays in place.


With the mesh in place I could begin applying the filler. As you can see from the items list, I used two types of filler. P40 and P38. P40 is reinforced with glass fibres which makes it great for situations where more strength is required. Then P38 is your standard body filler, this is much easier to sand and achieve a better finish.

So I started with the P40. I applied this to the the mesh on both sides and also covered the surrounding areas. I then sanded this as flat as possible.

Next I used the P38 over the whole flap. After leaving it to dry I used the sanding block with 180grit sandpaper to get the filler flat and seamless with the rest of the metal. At this point you can add more filler if required and repeat the previous step.

With the filler level, I continued block sanding working my way up the grits to achieve a smooth finish.


With with prep work complete, next task was the paint. First step is primer followed by the basecoat and then lacquer. Always read the instructions on your paints. I applied around 3 coats of each. Leaving the primer to set for 24hrs before sanding it with 400grit. Then applied the basecoat after cleaning the flap with rubbing alcohol and a tack cloth. I then left the basecoat for around 20mins before applying the lacquer.

So that pretty much sums up my fuel flap refurb. I’m happy with the results however there is one imperfection that I wish I sorted before painting, can you spot it?

Let me know!

Good luck with your own projects!

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