After 11 years plus 460,000 km, the roof of my BMW X3 (F25) looked like its clear coat had completely given up. A cheap cordless car polisher proved it had not.
Rain did not bead at all, and even after a wash it had no shine. It made me a little sad every time I looked at it.
This time I finally brought the paint back to life myself, with a dirt-cheap polisher from AliExpress. I am writing it down here as a record.
The roof before: no shine, no water beading
- Zero water beading
- No shine, even after washing
- Coating products did nothing
Rain just sits there in a flat film instead of beading.
What I used
Cordless car polisher
The polisher was a compact rechargeable one I bought on AliExpress. With no cord, it was easy to handle even up on the roof, and simple to use even for a beginner.
The rechargeable polisher. It cost about ¥2,500 (around $17).
Coating plus surface prep
For the coating I used Bliss, a Japanese car coating I have relied on for years. The surface prep product is also from Bliss. I bought the two as a set.
You only need a tiny amount of this kind of coating each time. Since I only apply it about once a year, one bottle has lasted me around ten years, so it is excellent value.
Polishing in the rain
Why a rainy day works well
It was the last day of Japan’s Golden Week holidays, and it was raining. As it turns out, that is ideal weather for polishing outdoors.
- Unlike a sunny day, the body panels do not heat up
- The compound does not dry out as fast, so it is easier to work with
- There is water everywhere, so pre-rinsing is easy
If anything, it was far more comfortable than working under a blazing sun.
Step 1: a quick wash
I used a sponge plus the rainwater to give the roof a light wash and lift the dirt that had built up.
Step 2: polish with the cordless car polisher
Next, I went over the whole roof with the polisher.
I worked carefully, letting it spin to take off the dullness, concentrating on the areas where water beading had completely disappeared.
Working across the roof.
Being cordless made it stress-free to use on a surface as awkward as a roof, and the battery lasted the whole job.
Step 3: wipe off, then coat
I rinsed off the leftover compound with water while wiping with paper shop towels. Then I spread Bliss thinly with a sponge, wiped it off again, and that was it.
Bliss can be applied to a wet surface, so light rain was no problem.
The roof after polishing
After the treatment the shine was transformed, and water beads up properly again.
I had thought the paint might be finished, so I was really pleased to see it come back.
After: the water beads up everywhere.
Before, for comparison.
Final thoughts
Honestly, with the roof refusing to bead water, I thought the paint was beyond saving.
Even a quick coat of product during a wash did not make water bead, so I assumed the clear coat was completely gone.
This time, properly polishing the surface before coating brought it right back. The AliExpress polisher I bought on a whim did a great job too.
My F25 has done a lot of miles. Still, it is funny how getting it a little cleaner again makes me want to keep enjoying driving it.
I am aiming for 500,000 km!
I will keep up the right maintenance to make it last as long as I can.
This article is also available in Japanese.
