My 90 Civic has been stored for 5 years, took it out for a tear and the brakes are spongy as hell. I`ve flushed/bled the brake system, and replaced the rear wheel cylinders... My question is what should i try next, Master cylinder, calipers?

 

a donkey

 

As long as there's no leaks and no cracked/bulging rubber lines, I would suspect the master cylinder.

 

Probably a MC is their isnt any leaks.

 

Bled properly?

 

disc all around or disc/drum? make sure the pads aren't hanging in the pad carrier (file the edges of the carrier AND pad down until it moves on its own with your hand, with minimal effort, then high temp anti-seize the contact points. same with that little tab on the shoe that acts as a slider on the backing plate. it's a cheap easy to do job, and if you still have a spongy pedal its your master cyl, but at least you know your brakes wont hang up

 

Honestly your brakes aren't going to be that "spongy" if your master cylinder is leaking past the seals internally.

If that's happening it's more like a gradual loss of braking, low engagement, or a generally shitty pedal feel, i.e. doesn't give much feed back because the hydraulic fluid isn't compressing evenly.

Spongy brakes is going to be air in the system. Period.

 

I'd say you did not bleed correctly.