Intermintent coolant loss at expansion tank

[Jake D]

So I know that the expansion tank is a known problem and I have had the intentions of swapping it out, but just have never got around to it. I had a leak about a year ago and I swapped out the cap because it was cheap and easy and I was hoping it might prevent extra pressure which might be causing the tank to leak. It didn't work, but strangely about 2 weeks later, the leak stopped.

Fast forward a year later and the tank started leaking like crazy again. I had to add about a liter of coolant each time I went to drive the car. This went on for about a month and I drove the car several times a week.

Topped up the tank like I had been doing, and now it hasn't leaked at all since. Has anyone else experienced something like this? I know the solution is to just replace the stupid tank, but I am still curious as why it seems to leak intermittently.

Car as never overheated and the temperature gauge has never got higher than usual..