In reply to a message from Red Phoenix sent Sat 17 Jan 2009:
Paul,
The appearance of the ‘ABS’ and ‘BRAKE’ warning lights when
you operate the brakes is indicative of insufficient brake
boost pressure in the Teves brake accumulator ball.
The most likely cause of that is failure / deterioration in
the accumulator sphere itself. An idea of the systems level
of performance in that respect can be judged from comparing
your car with mine.
Typically, when my car has been sitting unused (say,
overnight) 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 about
30 applications of the brake before the pedal �goes hard’
when servo assistance is lost.
It is this last sentence which is important, not the precise
timing mentioned earlier.
How does your car compare?
It would be less usual for the fault to be with the Teves
electric hydraulic pump itself (which charges the
accumulator), the combined pressure/ warning switch (the
blue/gold job next to the accumulator which switches the
motor on) or the ABS Pump or Main relays (which are
mentioned in the XJ40 on-line book in section 7.4.2).
BTW, those relays are not to be confused with the usual
culprit on the pre-'90 non-Teves cars, the ABS
‘over-voltage’ relay, which is mentioned in section 7.4.1 of
that on-line book.
If your '94 is post VIN 696460 weith the ‘hybrid’ X300 style
rear suspension, the lower shock mount must be of the
spherical bearing variety as opposed to the normal ‘solid’
rubber bush on the earlier cars. If not so equipped, there
is a tendency for the shock piston rod to snap at the top -
and that causes a knock.
Similarly, on earlier models where KYB shocks have been
fitted, they had a ‘batch problem’(?) which caused that
piston rod to snap at the start of the threads.
[Happened sometimes when the SLS was converted to standard
rear suspension using a cheapo conversion kit - has your car
ever had that conversion?]
Of course, it could simply be that the large foam isolator
(donut) on top of the spring has disintegrated, and that
will cause a metal-to-metal knock.–
The original message included these comments:
The ABS warning light comes on most times when I use the brakes and
the red warning light in the rhs lower section lights up with it as
well. The brakes work well and I’m sure it is a bad connection
somewhere. I will check the relay as in the XJ40 e book tomorrow
and at the same time try to find what is making the knocking sound
at the left rear. sounds like a shock mount.
Any further info would be appreciated.
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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