[xj40] need help identifying regular click-on road trip right now

XJ40
1

I just picked up a 1991 XJ6 Sovereign LWB in Dallas and am now driving to California. There is a soft but clearly audible mechanical double clicking sound approximately every 17 seconds when I’m going 70 MPH. If I slow down to 55 it occurs about every 21 seconds. It sounds as if its coming from the dash or steering column. Any ideas as to what it might be?–
gst552
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2

In reply to a message from gst552 sent Sat 27 May 2006:

I first thought it may by your trip odometer updating, since it
seems to be speed related. but I think it’s all digital, not
mechanical.–
The original message included these comments:

I just picked up a 1991 XJ6 Sovereign LWB in Dallas and am now driving to California. There is a soft but clearly audible mechanical double clicking sound approximately every 17 seconds when I’m going 70 MPH. If I slow down to 55 it occurs about every 21 seconds. It sounds as if its coming from the dash or steering column. Any ideas as to what it might be?

–
Pete 70 XKE (193K) 88 XJ6 (233K) 88 XJ6 (217K) 60 Mini
Severna park, Maryland, United States
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3

In reply to a message from Jaguarpete sent Sat 27 May 2006:

My dad, who is with me, thinks the clicking sound is digital and not mechanical. On the highway the sound is regular at 17 second intervals at 70 mph, but when I break I sometimes get clicks within a few seconds of each other.–
gst552
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4

gst552 wrote:

I just picked up a 1991 XJ6 Sovereign LWB in Dallas and am now driving to California. There is a soft but clearly audible mechanical double clicking sound approximately every 17 seconds when I’m going 70 MPH. If I slow down to 55 it occurs about every 21 seconds. It sounds as if its coming from the dash or steering column. Any ideas as to what it might be?

gst552
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Welcome and best of luck with your new Sovereign

Not really from the description but it is something connected with the
rotation of the wheels apparently since its speed related.
I’d start with checking them out on a lift before taking the wheels off
and checking for any other issues.

Oh BTW there really is no LWB XJ40’s in the USA. All XJ40’s have a
wheel base of 113" except the the 50 or so UK Daimler Double Six
Majestics made in the late 90’s and they were X300’s not XJ40’s. The
LWB designation arose years ago on the Series I or II XJ6. I don’t
recall exactly.

The only long wheel base XJ40 were the 50 or so UK XJ6 Daimler Majestics
which were sent out from the factory cut and lengthened 5" to 118".
Drove me nuts trying to figure out where the extra 5" was in my 113" WB
US VDP Majestic

Jay 90 Vanden Plas Majestic–
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5

In reply to a message from gst552 sent Sun 28 May 2006:

OK, that narrows it down.

If you hear it more frequently when you apply the brakes, my
guess is that you are hearing a relay energising to switch
on the Teves electric pump for the brake boost / ABS system
to top up the brake accumulator.

Since you hear it at speed without touching the brakes
suggests that there is a gradual leak-down of accumulator
pressure but I can’t think how that is related to road speed.

If it is brake accumulator related, you should be able to
reproduce it with the car stationary, engine running, by
applying the brakes a few times. Normally, on a fully
charged accumulator, you can hear the Teves pump cut in to
top-up the accumulator after two or three applications of
the brakes. Check if the relay which does that produces the
same ‘click’ as you hear at speed.–
The original message included these comments:

My dad, who is with me, thinks the clicking sound is digital and not mechanical. On the highway the sound is regular at 17 second intervals at 70 mph, but when I break I sometimes get clicks within a few seconds of each other.

–
Bryan N, '91 Sovereign 4.0 L, (RHD)
Cambridge, United Kingdom
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6

In reply to a message from Bryan N sent Sun 28 May 2006:

Jay, thanks for the clarification on the LWB.

Bryan, you describe thw symptoms precicisely. Does it signify a problem I should have fixed?

I’m pleased to report that I successfully made it from Texas to California.–
gst552
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7

In reply to a message from gst552 sent Tue 30 May 2006:

Well, you should first check that the brake accumulator is
holding pressure.

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
    point)
  • 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
of times.–
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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