Cherokee Brake Problems-Brake Booster?

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tyytyy22 - 30 Jan 2006 01:08 GMT

When i'm driving, sometimes there will be brake pressure and somtimes
there won't. If i apply pressure for a few seconds, the pedal loses
presure and goes to the floor. I have to pump the brakes to get the car
to stop. I tried bleeding the brakes and got through the back to wheels
fine, but when i tried to bleed the front right brake, air bubbles kept
coming out. After refilling the resivoir for the 3rd time (it never got
completly empty), i got the idea that it might be somethign more
complicated. I was able to bleed the front left with no problems but
the same thing kept happening when i tried to drive it. I checked all
the lines and can't find any leaks, but i have an oil leak so i might
be missing something thinking its just oil and not brake fluid. There
is some black fluid underneath where the brake booster connects to the
master cylinder but i don't konw if its coming out of there or is oil .
I can also hear some air come out of the brake booster inside the car
but i dont' know if that is normal. My brake fuild is also pretty dark,
i know i should flush it out and replace it but could that be the
problem? I don't know too much about brakes
and i don't want to take apart the whole system before i know what to
look for. Any ideas?

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DougW - 30 Jan 2006 01:42 GMT

tyytyy22 did pass the time by typing:

> When i'm driving, sometimes there will be brake pressure and somtimes
> there won't. If i apply pressure for a few seconds, the pedal loses
[quoted text clipped - 15 lines]
> and i don't want to take apart the whole system before i know what to
> look for. Any ideas?

If your getting fluid from between the booster and master cyl or
coming out the bottom of the booster (and it's not spilled or leaking
from the connections) then your master cyl needs to be rebuilt/replaced.
Front and rear are seperate pistons in the master cyl.

Barring that I'd be checking the proportioning valve for leaks.

Loosing pedal pressure (without seeing a massive puddle of brake
fluid under the Jeep) makes me about 90% sure it's your master cyl.

Signature

DougW

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tyytyy22 - 30 Jan 2006 02:21 GMT

thanks for the help. if i took out the master cylinder and replaced all
the parts in one of these kits:
http://www.tellico4x4.com/catalog/product_info.php/cPath/1714_307/products_id/13305
do you think it would work? or should i just buy a new master cylinder?

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billy ray - 30 Jan 2006 05:27 GMT

If depends.... do you have the hones, etc that would be required to do it
yourself?

Master Cylinders don't cost that much to buy remanufactured and if you have
another vehicle you can remove your current one beforehand and avoid paying
the core charge ($20-$25) They will also (usually) come with a small kit
for bleeding before installation.

As a final note I would use suggest that you use the synthetic DOT 4 fluid
instead of the standard DOT 3. It is less attractive to water which leads
to less corrosion in the system (the black gunk), has a higher boiling
point, and only costs an additional $1 per quart.
http://www.valvoline.com/pages/products/product_detail.asp?product=51

> thanks for the help. if i took out the master cylinder and replaced all
> the parts in one of these kits:
> http://www.tellico4x4.com/catalog/product_info.php/cPath/1714_307/products_id/13305
> do you think it would work? or should i just buy a new master cylinder?

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Dave in Columbus - 31 Jan 2006 05:53 GMT

>If depends.... do you have the hones, etc that would be required to do it
>yourself?
[quoted text clipped - 14 lines]
>> http://www.tellico4x4.com/catalog/product_info.php/cPath/1714_307/products_id/13305
>> do you think it would work? or should i just buy a new master cylinder?

A big plus with the better rebuilt master cylinders is the installation of
a bronze cylinder which is much less likely to corrode than the aluminum of
the original bore.

Signature

Dave in Columbus

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Mike Romain - 30 Jan 2006 14:28 GMT

You have too many threads going on.

I gave up rebuilding MC's years ago. The kits just plain don't work
because you have to hone out the cylinder and they 'don't' sell you
oversized O-rings or cups to make up for it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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