it's not a drum brake master cylinder by any chance?

with a line pressure valve?

never thought of checking the struts, will look into that, maybe do a complete service and parts replacement on them. thanks

I would have a look at the caliper itself and check the condition of the bore and piston. Being quite old I have found all brake parts of this era to be full of crap or the seals themselves needing replacement.

I installed a set of stanza struts a while back in my ute, problem is i'm at my 4th different brake master cylinder. the original one started leaking so i replaced it with a new one that tuned out to be faulty, replaced again and again faulty, bought a different make and works, but now the brakes keeps building up to the point where it's undrivable and i need to bleed it again and drive for about a day and same problem. it seems to build up the first time I brake really hard. any help please? it's the standard ute brake cylinder without the booster