I have a 1991 jeep cherokee limited , so lately iv been driving it and out no were my breaks started to make air noise everytime i would push down on them, as well the peddle was going to the floor, another thing if i cotinue to push the peddle down hard it make my jeep idle higher, now i have bleed them many times n the peddle still goes to the floor n ot hardly breaks, now i do have abs but.it was never connected , had ot for 3years n it just started happening , now im not sure if it might be the break booster or MC or the diaphragm? Any ideas ??

 

Vacume problem. Start checking vacume lines from booster to motor. will cause all of the symptoms you are describing. If you can't find leak its the booster. Try a tube up to your ear while its running and probe around vacume canister and vacume lines.should hear where leak is.

 

Rite on i will do that soon as i get back home, any specific hoses? I know theirs one that runs from the booster to the air manifold

 

That is most likely the one. I would check all that come from the booster though. Cant remember off hand how many there are.

 

Well i checked all the hoses they seem to be fine, the air nose absolutely only happens when i push hard on the peddle n it stays hissing n u hear it as when wen u push on the peddle but only stays hissing when u hold it down to the floor , tje peddle is hard when the jeep is off soon as u turn it on it gets really soft

 

I would check diaphragm in master if it looks good then its the booster. If you can check vacume line with gage as you press brake it may show you what is happing. I would try to have someone press brake as you descibe and listen with a stethoscope or small hose to determine where noise is coming from. Gonna be the fastest way to determine problem.

 

K , will do thanks, im actually just gonna.replace the booster with a 93 cj booster is bigger but more efficient im heading over to the junkyard

 

So iv changed the booster one from the junkyard n it seems that i might of got a.bad one diaphragm is still hissing, n i just replaced the master cylinder brand new n my breaks still feel weak

 

master cylinder seems to be the culprit. brake pressuire is bleeding through internally through the seals on the rod. my guess

 

Cant be i just replaced the master cylindet.brand new, im guessing its the break booster since i did get from the pik n pull

 

You have some odd breaks, I usually sit down eat a snack and drink a pop or something for 10 min or so.
Now I'd we are talking about brakes that makes more sense, sounds like that JY brake booster is failing on you. What can you say it's a JY part could last you 15 years or it could be the reason the jeep was in the JY anyway, you never know.

 

Well its an xj n im using a break booster from a 92 xj sport , but since i replaced the master cylinder with a brand new one im going to simply buy a brand new booster n c c if thats the cause of my issues! Thats my xj last weekend at pismo.beach.dunes

 

Lol I think that still flew above a couple heads.

 

Lol didnt fly above anyones head atleast not mine, i doubt another sarcastic response to a matter of absence of humor was not in my state of mind since i chose to ignore a bundle of words.

 

Hi I have a 96 Jeep grand Cherokee limited changed calibers brakes and bled the breaks and it is tight when the car is off but when you crank the car the breaks go to the floor I'm stumped is there still air in the lines or what please help