Hard pedal

[rickandbev16]

Hi guys,
Fishing around for ideas on this one. Car is a 1.6 diesel auto 2016.
Drives fantastic in every respect BUT left overnight the brake pedal
goes solid. Never used to, and if only left for a short period doesn't
Obviously wouldn't normally be a concern but only just started doing
this and and anything weird on brakes is always a concern.
Anyone got any thoughts ???

[deejay_xb]

maybe you park the car on inclined terrain and it's activating the brakes so the car does not go back

[oilyrag]

Might be worth seeing if the servo is operating - put you foot on the pedal and crank the engine over to start it - as it starts the pedal should sink to the normal brake biting point. 
Switch off and press the pedal a few times and the pedal will harden up as any vacuum is then 'used'.
I guess as a diesel it will have a vacuum pump for the servo - this might be playing up and allowing vacuum to bleed off as might the servo or any vacuum hoses.

[cancunia]

It will almost certainly have a vacuum pump to supply the brakes and the turbo. Does the pedal go 'soft' as soon as you start the engine? If so, as oilyrag says,it's probably some vacuum bleed over time, worth checking hoses etc.
The other thing to note is that diesels often get 'brake pedal creep' where the pedal goes soft and travels further than expected as the vacuum is deliberately bled by the system when the pedal is pressed while idling to prevent overloading the calipers with fluid pressure.
It's odd that it's suddenly started doing it though so well worth a check, but tbh losing vacuum overnight or over a few hours is what I'd expect.