Soft Brakes...

I have had an issue with my brakes lately and I can't figure it out.

The resevoir has had a small leak, so I've just been topping it up every other tank of gas. Anyways it was about half full (or half empty for you pessimists) and I needed to hammer on the brakes at a stoplight. My parking brake light came on and since then my brakes have had a LOT of play in them before they grab and even then they're not grabbing hard at all. So I figured I'd top it up and see if that made any difference. I filled it and drove it around a bit with no change in the brakes. The lights still on and I have lots of fluid still.

I originally thought air in the lines, but even if I pump the brakes, they don't firm up at all like I'm used to when they need bleeding.

Suggestions for where to start?


Oh and some specs on my Jeep.... it's a '93 AW4 with 4.5" lift and I'm running 33x12.5's.

Thanks in advance guys!

Do you hear a vacuum leak when you are pressing on the brakes? If so you need to replace the brake vacuum booster. If not, it is probably the brake master cylinder that needs replacing due to internal piston cup and cylinder wear thus causing internal leakage (Not enough pressure generated).

Also sounds like you have an external leak somewhere so check the lines and each wheel for signs of a leak.

Mike McGinness
South Houston, TX

Thanks, I'll check into it today and hopefully fix it up.

Well I just changed out the master cylinder and the resevoir from another 93 XJ I have here (my parts jeep) and I bled the brakes... but the problem is still there. The dashlight went off though, so I don't know if that's a good thing, but I'd assume it means I'm in the right direction.

Anyways, now when the jeeps off and I pump the brakes, they get nice and firm right away. But once I turn it on, they immediately get mushy again and lose all pressure.

Help?

I had the same problem a few weeks back..
If you bled the brakes and changes the master cylinder and still have the problem it has got to be the booster or a leak in the vacume hose, tinker around with it and see what you come across.

I'm going to try swapping in the booster from my other Jeep to see what happens tomorrow. I have a new master cylinder ordered too so that I can completely rule out that as the problem, but it won't be in till tuesday. So I'll play with the booster and see how it goes.

How long should swapping boosters take approx?

are your rear brakes worn out?

Porportioning valve for sure get one and you will be happy