308 QV Creaking Sound from coolant tank

Hi Gents

I would like to seek some advice please, I took my 308 QV for a long drive after two months of lockdown, and noticed a couple of unusual things, probably me being paranoid.. but here goes

1. I notice that the car got up o 195 degrees after only two miles.. which it normally take around 5 miles for the gauge to even move? I guessed this may be nothing more than a sticking thermostat?.. but secondly
2. I noticed after the run, and the car was sat in the garage about an hour later, there was a small creaking sound every minute or so coming from the coolant header tank, I undid the Rad cap to released the pressure when it was safe to do so, and the noise stopped... I put the cap back on, and it started again after a few minutes....this went on for the next two or three hours? And then finally stopped.
so I guess my question is... is this pressure related creaking sound something to worry about?.. or Is this fairly normal? And maybe a new cap and thermostat is in order?

any advise would be greatly appreciated

 

Hi... not sure how old the cap is, but I’ll change it regardless... however.. I took her for another 100 mile trip and she behaved perfectly... and funnily no creaking sound maybe where it hadn’t been driven for two months... it just had a small hiccup Thanks for the advise