My brakes are very low and feel spongy. my master cylinder was leaking alittle so i replaced it with a brand new one, did all the bench bleeding. with no better result. So i figured air in the system so i bled the brakes. no better, So i bled them again and again and again with no result. after noticin that the master cylinder was leakingagain i got another one. and that one began to leak so now im figured its not the master but maybe the brake booster push rod so i adjusted that just today. obviously no result. just wondering if anyone has had this type of problem and could help me out. the brakes will stop me but not til there almost to the floor. also brakes are hard with truck off. so i know the booster is good.

 

Check for vacuum leaks on the line running to your booster.

 

Your master cyl. should never leak from the back were the plunger goes. you might have a bur on the plunger scratching the cylender or the rod is adjusted too long and when you bolt it down you are breaking the seal. If you are leaking from the back of the master you have a problem with your master not the booster.