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brake question

90 xj

NAXJA Forum User
Location
stl mo
i have a quick question i have a 1990 xj and i think that the mastercylinder is bad( sometimes it stops good sometimes and other times not sometimes i can pump it and it gets better, i checked the wheel cylinders so i think that the seals in the master cylinder are bad) i was wondering if the newer style with the bigger booster and plastic resivor will work or if any one has done this thanks
jake
 
maybe there is air in the brake-lines?
or the brake-fluid is too old and it gets cooking?

first you should test the brake fluid - there is equipment to test how high is the max-temperature of it..
if this is ok .. try to bring air out of the system ... (maybe you need some new fluid when doing this).

if this is ok too ... and you are sure there can't get in new air ... you are maybe right .... but i never had that ..
 
Somethig to keep in mind, is that the master cylinder is actually, two master cylinders in one. One half for the fronts and one half for the rears. If you get a leak in the rear, the front part of the resivoir goes down and vice versa. If the master messes up, it is often the fronts or the rears that give trouble, rarley both. And when half of the master starts to fail, the brake trouble light will come on, because the two sides make (radically) unequal pressure (there is a pressure switch for this purpose).
I´ve had the brakes seep (leak) at the wheel cylinder, but also at various fittings in the brake lines.
If the resivoir has run dry, it can sometimes be problematic to get all the air out of the master cylinder, but again the brake light will come on, because of the uneven pressures.
If there is air in the system, the brake light often won´t come on, until the air problem gets really bad.
You can often hear the vacuum booster hissing (when the brake is lightly applied) when there is a diaphram leak.
ABS?
 
If your verhicel has ABS, it is probably the Bendix-9 or 10 system, which has a recall (#702) for the master cylinder and ABS pump/motor assembly. Both have a lifetime warranty.
 
90 xj said:
i have a quick question i have a 1990 xj and i think that the mastercylinder is bad( sometimes it stops good sometimes and other times not sometimes i can pump it and it gets better, i checked the wheel cylinders so i think that the seals in the master cylinder are bad) i was wondering if the newer style with the bigger booster and plastic resivor will work or if any one has done this thanks
jake

The newer style MC will NOT fit the older style booster. If you want to upgrade to the newer MC, you will need to upgrade to the newer booster, and will need to fab some new lines between the proportioning valve and the MC.

Do a search on this, and you will find lots of guys have done this sucessfully.
 
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