Brake Question ???

[Lead Dog]

Allright, I have a 04 Wrangler unlim. with a 8" Fabtech suspension, it has replacement brake lines. Here's the problem.... when in 4 low the brake pedal sometimes goes away !!! I mean it will out of nowhere allmost hit the floor and then it will come back??? I drive this Jeep almost eveyday and it never acts up!!! The only time it does is when it's in 4 low.

What could it be? :confused:

[Dukes69]

bad master cylinder maybe? Could be that stock jeep brakes suck and require you to push that far.

[Old Fart]

What kind of replacement brake lines? Brake lines swelling would give that type of symptom (and it would be much more noticible in low range)

[Lead Dog]

What kind of replacement brake lines? Brake lines swelling would give that type of symptom (and it would be much more noticible in low range)

I'm sure there some kind of mass produced stuff? They came with the kit from Fabtech!

Why more noticible in low range? and why not in every day traffic?

[Old Fart]

Don't know. The only other thing I could think of was a vacuum leak initiated by putting it in 4WD (does it do it in 4WD High Range)

Torque gets multiplied big time in low range, could be causing you to push harder (although with a stock t-case, it shouldn't be _that_ much)

[Lead Dog]

No! It does not do it in high. And why wouldn't it do it in the daily driving times??? Seams that vacuum would be it's lowest in bumper to bumper traffic??

[aston]

My YJ has (had!) a vacuum operated disconnect on the front axle. I don't know if the TJ has such a device.

Anyway, what if there was a vac leak at the disconnect that only occured when 4WD was selected. And this leak bled down the brake servo.

A wag on my part.

[Jeri Lyn]

No! It does not do it in high. And why wouldn't it do it in the daily driving times??? Seams that vacuum would be it's lowest in bumper to bumper traffic??

Vacuum is highest at idle, lowest at wide open throttle.