Brakes have been awesome until these last few days. When I back out of our garage I always test my brakes several times because the driveway is very steep and ends in a ravine! When I start the car, for the first minute or so, (whilst the hisser is working), and back out of the garage testing the brakes and the brakes work once or twice as normal, then need massive foot pressure to stop like there is zero vacuum for two or three attempts then they go back to normal.
I have been for several test drives and the brakes work well all the time, I can get a lock up, the car stops okay, its just during start up that this happens. It happens if the car has been sitting for a few days or a few hours, same thing.
Though my car is a 1967 420G it was built in August 1966 so the system is like a Mark X Tony AWG in another thread describes it as this : 4.2MKX 66-67 had a booster with a band clamp that holds the clamshells together, and type B master cyl, Mine is this clamshell variety.
I tested all my vacuum lines for leaks with starter spray and no increase in idle.
What other checks can I do to discover the issue and or easy fix before condemning the booster?
If it is the booster is there a repair kit for this type and if so from where?
Are there any booster shops that can refurbish this type?
Should i simply go ahead and install a XJ S1 as Tony suggests and get it over and done with?
Thanks for your advice