I bought a CJ-5 with all drum brakes and they are very spongy?

start by flushing out the old brake fluid -- start with the rear passenger side wheel (farthest from master cylinder). Put a clear 1/4" hose over the bleeder and into a jar, make sure you have plenty of extra brake fluid, open the bleeder and pump the brakes until the fluid comes out clear keep checking fluid level at MC. then do rear driver side front passenger side and last the front driver side.

If that doesn't fix the problem and you know that the brake cylinders are not leaking then you might have to replace your MC. search on line for possible upgrades (my CJ7 has a Corvette MC) good luck

Sounds like you still have air in the lines. Might want to flush system and start over with fresh brake fluid.

i'm a coloration tree mechanic so do no longer take this to the financial employer. i could wager that rear brakes would be so as. a minimum of do an inspection of the beef left on the footwear. there is likewise the prospect that the warmth created ought to have warped the drums. verify them for tolerance. yet another theory is that in line with probability the warmth would have affected the viscosity of the brake fluid. it is not that i'm effective of this, yet in line with probability extra proficient mechanics could have a remark in this. yet i'm questioning that if the viscosity is decreased, it ought to describe the "sponginess". ? risk-free making use of grasshopper!!!

may want to rebuild the whole drum unit on the wheels depending on how old the jeep is. then flush out the whole brake lines. if you have rubber hoses connecting to your brakes. they maybe worn and are swelling when you apply the brakes. might want to replace them too.

remember 4 wheel drums dont have the stopping power or feel like disk brakes have.