mhead
NAXJA Forum User
- Location
- Encinitas, CA
Hi All,
I've a 1992 XJ 4.0 4x4 auto tranny. I have about 3K miles on new pads and rotors. I've tried two types of new pads. This vehicle HAD the ABS unit, which I removed. I simply routed master cylinder outs to front and to back brake hydraulic lines, eliminating the ABS.
Under normal brake pressure this jeep stops normally. However in an emergency situation very hard brake pressure does not cause the front wheels to lock up. It seems like the booster assists up to some point but after this point further braking force must be applied by foot onto pedal without much boost. i don't recall when this problem appeared.
When started with foot on the pedal the pedal sinks in the expected way.
After stopping engine the brake assist seems only to last about 30 seconds. I guess the one-way vac valve has a leak or possibly there is some other leak into the booster.
I'm casting about for some explanation. I suppose if the manifold vacuum were low then there would be a limit to the amount of boost I could expect. Anyone know the expected vacuum at idle or some RPM?
Maybe there's a leak in the booster that lowers the overall vac available?
I'm really lost on this one and will appreciate suggestions on how to test the booster or other parts in the system.
Thanks!
Mike
I've a 1992 XJ 4.0 4x4 auto tranny. I have about 3K miles on new pads and rotors. I've tried two types of new pads. This vehicle HAD the ABS unit, which I removed. I simply routed master cylinder outs to front and to back brake hydraulic lines, eliminating the ABS.
Under normal brake pressure this jeep stops normally. However in an emergency situation very hard brake pressure does not cause the front wheels to lock up. It seems like the booster assists up to some point but after this point further braking force must be applied by foot onto pedal without much boost. i don't recall when this problem appeared.
When started with foot on the pedal the pedal sinks in the expected way.
After stopping engine the brake assist seems only to last about 30 seconds. I guess the one-way vac valve has a leak or possibly there is some other leak into the booster.
I'm casting about for some explanation. I suppose if the manifold vacuum were low then there would be a limit to the amount of boost I could expect. Anyone know the expected vacuum at idle or some RPM?
Maybe there's a leak in the booster that lowers the overall vac available?
I'm really lost on this one and will appreciate suggestions on how to test the booster or other parts in the system.
Thanks!
Mike