American Motors: 1978 cj 7 brakes, piston seals, fluid contamination

Question
found out that rear was not working, i got them free and was working ok then the fronts started locking up, you can open bleeder valve,or take loose the line, or pull out the proportional valve spring and it frees up,it got disk on front and drums on rear ,thanks David t

Answer
It sounds like you might have a problem with your master cylinder. There is a push rod between the booster and master cylinder. If it is misadjusted, too far out, it can cause the brakes to apply. Another possibility is brake fluid contamination. If the brake fluid is contaminated, the piston seals could swell and cause the brakes to apply. Or the wheel cylinders could be seizing up due to contamination and not releasing. You could replace the master cylinder, flush the hydraulic system and use fresh brake fluid; providing the wheel cylinders and calipers are not contaminated.
Kevin