I was in the cab of my bay today and noticed what I thought was the cap unscrewed from the brake fluid reservoir under the drivers seat, it wasn't, the centre of the cap was sheared away from the sides.... So the threads are still threaded but the middle is 'out' ! I haven't been near there in ages so I'm tempted to blame my two kids for messing with it, before I whack them with a fan belt, is there any other possibility ? Anyone got a spare? lol....
You have over tightened the cap. I had the same thing 40 years ago on my Beetle, teaches you to ony finger tighten it!! Tony