Is your brake fluid cap unable to tighten? Is it normal that I can't tighten mine?

The brake fluid cap on the Mazda6 is prone to damage. If it can't be tightened, it's broken, so you should replace it.

You can tighten it. I had a similar issue after changing the brake fluid; it wouldn't tighten and would come off easily. I bought a new domestic one from Taobao for 19 yuan and it worked fine.

The same thing happened before. I bought a new one and it couldn't be tightened either.

Normal!