Brake pedal is very soft until last two inches of travel

I have a 1992 Jeep Cherokee Laredo with 185000 miles and ABS brakes. I have replaced front rotors and pads and everything (springs, drums, pads)on the rear besides one of the two wheel cylinders. No sign of brake fluid leaking. My brake pedal is very soft in the first 4 inches of travel and hard in the final two inches. The brakes still pump up very well and pump to very hard! Stock brake booster, stock master cylinder. Brakes haven't been bled in a looonng time. Any input would help! Thanks!

I think that's a bad brake booster... I think. Because my brakes do that, and my booster is confirmed bad. However, I also have other issues...

Quills said:

I have a 1992 Jeep Cherokee Laredo with 185000 miles and ABS brakes. I have replaced front rotors and pads and everything (springs, drums, pads)on the rear besides one of the two wheel cylinders. No sign of brake fluid leaking. My brake pedal is very soft in the first 4 inches of travel and hard in the final two inches. The brakes still pump up very well and pump to very hard! Stock brake booster, stock master cylinder. Brakes haven't been bled in a looonng time. Any input would help! Thanks!

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start by bleeding teh brakes, if that doesn't work I'd go after the master cylinder next

Definitely bleed the system....especially since you installed new wheel cylinders.

Get all the old fluid out....anytime you OPEN the system, which you did if you replaced them, you must bleed it since you've introduced air into it.

Good Luck.

Try adjusting your back brakes.

Dude....


Trust me. If you can pump them up it eliminates the master cylinder, becuase the pressure is holding.

It is very rare for a power booster to go out but it does.

Bleed the system out.

Start in the Right Rear, Left Rear Right Front and Left front in that order. Make sure that the fluid coming out of each corner is nice and clean. Check the MC after each corner is done to insure that you done get anymore air back into the system.

Also it is advisable to replace calipers, and wheel cylinders in pairs...you might want to just go get another wheel cylinder for the other side.

Unless there is something radically wrong with your brakes....your problem will be solved.

Done the auto repair / wrecking thing now for 18 years. Brakes are actually simple to do.

Then adjust the rears, you'll find doing it now will not solve your problem.

Good luck again.

iratefla

Note look in your post. If you replace a wheel cylinder or even open any of the lines to the hydraulic system bleeding of the brakes must be performed. That is the problem. The air compresses and the fluid does not.
:wave: Your hydraulic guru

Red91 has it, if you replaced a wheel cylinder and did not bleed, that's almost 100 percent what is the matter, but a couple of added points.

If the booster is bad, the pedal will be firmer, not softer, and braking effort will increase. A bad booster will not produce a low pedal.

A dual master cylinder will behave as stated if one circuit is drastically in need or either bleeding or repair. It will be soft until near the end, when it will operate the good circuit alone.

A bad master cylinder might still pump up. Often when the MC goes bad, it will stop all right when pumped up or hit hard, but bleed down when under steady pressure. If it always goes low, and always pumps up firm, it's probably not that. But every once in a while, it's a good idea to put your foot firmly on the pedal (pumped up if necessary) and just hold it there, to see if it stays up. If it sinks slowly under pressure, and there's no leak, the MC is going out.

This also happens to me, I have no fluid leak but when I step on the brakes I hear an air leak, can this be the booster leaking? Any info would be appreciated, Thanks all

denn34 said:

Try adjusting your back brakes.

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x2, that sounds like the issue (or air in the lines). I had that issue on my 92 XJ a few years ago, the self-adjusters needed to be replaced.

SketchyXJ said:

This also happens to me, I have no fluid leak but when I step on the brakes I hear an air leak, can this be the booster leaking? Any info would be appreciated, Thanks all

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If you hear a sucking noise when you apply the brakes, then pull the check valve from the brake booster and listen for vacuum.

X96....lol. I agree...replace the other wheel cylinder, bleed and you should be good to go.
After replacing my entire brake system (-power booster) I actually enjoy doing them now. Took about a half day(mostly bending/flaring) but it was instant gratification. My pedal only travels about an inch b-4 they start to grab, thats a good pedal for a XJ.

Is the chech valve the little black elbow piece with the vavume line attached? Do I just listen for air in there? Whats good to hear and bad? Sorry for the questions I just dont understand. Thanks