Hey team,
Recently had an issue with my brakes that is now sorted, but could not find any info on someone having similar symptoms so thought I would share in case someone ends up in the same spot and comes looking for help.
On start up the brake warning light would come on (indicating lack of vacuum). However in most cases if the car was driven for about 100m the brakes would sort themselves out and the light would turn off and the system was fine until turning the vehicle off. How annoying this was would fluctuate sometimes it would be sweet by the time I pulled out of the driveway, other times it would stay out of vac until 20min later.
I checked the hoses and thought it was a faulty vac pump as getting the revs up usually helped, but when I tested that it and it was fine. I replaced the hoses and put one with a check valve in just to make sure the system was set up properly. I also changed the wee solenoid at the bottom of the brake booster... Fixed, for about 3 starts and then the problem returned and gradually got worse.
Ended up being the brake booster itself, swapped that out, bled the brakes and boom, its awesome now. Assuming that that Diaphragm has a break in its seal, but no real clue.
They fix itself seemed pretty systematic (following instructions found on here as per what to check). Just had not seen anyone with the same symptoms so here we are. Hopefully makes life easy for someone in the future. Cheers.