Power Brake Problem

What would cause a 1991 Jeep Cherokee limited to have no power brakes? the Master cylinder was changed but that didn't help there is still no power. :banghead:

Check the vacuum lines to and from the master cylinder, and also make sure there is enough fluid in the system. You may also want to bleed the brakes to be sure there isn't any air in the lines. All of these problems will greatly reduce or even eliminate braking.

I should also mention this has a ball on the mastercylinder, and we changed the mastercylinder setup, Vacuum lines all good, it was bled, no leaks and the fluide level is good.

WHat happened first, reason for replacing M/C. Usually if the MC goes bad, you will either have a mussy pedal, or it will go to the floor with no responce from the brakes. If you have a hand vac pump, remove the vac line to the booster, and try to pull a vac on it. If it won't hold a vac then look at possibly r&r the booster. Do you have any brakes at all? ie. engine off, firm pedal when applied.

We purchased the vehical from another owner, when we got the Jeep it the breaks were there just enough, though neutral got used alot just to be safe when stopping. We changed the MC because of that problem. As I pointed out this MC has a ball on it, there is no booster on it. There are breaks on it persae a bit better then when we got it, but not the best they could be.

Now one person told me that we have ABS equipped vehicle, and that they do not employ a conventional vacuum operated power booster on that model year with that feature. Also that the ABS on that model year is problem-prone, and that switching the brake booster/master cylinder to a conventional, non-ABS variant.

I don't know yet what to think, I have alot already put into it, and otherwise it is a great vehical so I am looking at all the options and that requires some advice which is why I asked.

Fist I have to apoligize for missing the key phrase about the bubble. You do indeed have the abs system brakes. I too had this on my 89 XJ. This is what you need to do, go to napa and get a M/C and booster ( they come together, and cheaper), stop by your local junk yard and pick up the puportioning valve for that system, along with the front brake lines, taking care to how it looks before you remove it. Now once you have all the old abs stuff removed ( becareful some other things are running with the abs wiring) situate your P-valve and lines. Good time to install new rubber lines if the old ones are cracked badly.( the ones that run from the metal lines to calipers) INstall your booster first, take and turn out the threaded rod a couple turns ( the one that goes into the M/C. Then bleed out you M/C then install it and attach your lines. carry out your typical bleed out RR/RL/FR/FL. ALso attack a 3/8" vac line from your intake to you booster. Your brakes should work well, you'll notice a little travel in the pedal before you get responce, but this is normal. This is a little tricky, but you can do it in a week-end if you have all the stuff together. Oh, and to get more storage space, lift up your back seat, on the DS, remove the old abs processor. Good luck.

Hi I have a 2004 grand cherokee that the breaks simply go to the floor every now and again. I know its in the abs but not sure how to fix..