In reply to a message from gst552 sent Tue 30 May 2006:
Well, you should first check that the brake accumulator is
Here’s a write-up I did for the archives on how my (good)
system performs. Check yours against this:-
Teves Brake Boost / ABS pump performance
Typically, when my car has been sitting unused so that any
residual pressure in the accumulator has long since
dissipated, on turning on the ignition (without starting the
engine), the pump motor runs, the ABS light extinguishes
after 32 seconds, the ‘BRAKE’ light extinguishes after 35
seconds and the pump stops after 42 seconds.
With the ignition still on, the pump will re-start on the
second application of the brake and run for 3 seconds to
recharge the accumulator.
Then, with the ignition switched off, it usually takes
exactly 30 applications of the brake before the pedal �goes
hard’ when servo assistance is lost.
According to the Jaguar Service Manual, the (nominal)
pressure in the accumulator on a Teves equipped car at which
these events occur is something like this:-
- Starting pressure = zero
- ‘ABS’ light extinguishes in 32 seconds at ~1400 psi
- ‘BRAKE’ light extinguishes in 35 seconds at ~1550 psi
- Pump stops after 42 seconds at 2700 psi (upper switching
- After one or more brake application(s), pump re-starts at
~2000 psi (lower switching point) and runs for ~3 seconds to
‘top-up’ the accumulator.
- With the ignition ‘OFF’, as the accumulator pressure
dissipates (either through natural losses or brake
applications), the warning switches for the ABS and BRAKE
lights are actuated at ~1500 psi [which will then illuminate
the warning lamps when the ignition is turned back on].
Report back the equivalent figures on your car so that I or
someone can advise if you have a problem. I guess something
is wrong, because my car doesn’t ‘click’ as you described
during cruise - well not unless I touch the brakes a couple
The original message included these comments:
Bryan, you describe thw symptoms precicisely. Does it signify a problem I should have fixed?
Bryan N, '91 Sovereign 4.0 L, (RHD)
Cambridge, United Kingdom
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