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Brake Pressure Light

fless1
Posts: 180
Joined: Tue Jun 07, 2011 8:27 am
Location: Essex

Brake Pressure Light

Postby fless1 » Thu Feb 01, 2018 1:51 pm

I have brake fluid pressure light coming up. Done the brake pedal test with engine off and managed 39 pumps before it went hard (ooer)

Fluid is at max and there’s no reduction in braking
ABS light goes off after engine starts and doesn't come back on.
VCM shows PAD if pushed when the light flashes on but I’ve had pads checked out and all ok

VCM shows FAIL when ingnition on 2 and accumulator priming

Suspect low-pressure/warning-lamp switch?
'94 XJ40 - VIN 703709

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pimgmx
Distinguished Mbr
Posts: 2882
Joined: Tue Jul 08, 2014 12:07 pm
Location: Haarlem area, Netherlands

Re: Brake Pressure Light

Postby pimgmx » Thu Feb 01, 2018 3:04 pm

Perhaps an open door: did you also check the brake pad wear sensors?
If worn too far they will continue to give a 'worn pad' signal, even with brand new pads...

the daily: 01 S8 D2 http://bit.ly/2kIwP4m
the eyecatcher: 93 HFM 4.0 Insignia http://bit.ly/1iGrmsU
the GT: 89 JFJ XJS http://bit.ly/1WQGpC5
the problem child: 95 HFB X306 http://bit.ly/1cW11DN
the pocket rocket: 97 2.8 E36/7 http://bit.ly/12IfE7B
the ex-daily: MY94 BRG 3.2 http://bit.ly/14GTNrq

fless1
Posts: 180
Joined: Tue Jun 07, 2011 8:27 am
Location: Essex

Re: Brake Pressure Light

Postby fless1 » Thu Feb 01, 2018 3:47 pm

PADS weren't changed, was told not required, but sensors are on my list of suspects - easy to install myself?
'94 XJ40 - VIN 703709

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pimgmx
Distinguished Mbr
Posts: 2882
Joined: Tue Jul 08, 2014 12:07 pm
Location: Haarlem area, Netherlands

Re: Brake Pressure Light

Postby pimgmx » Thu Feb 01, 2018 4:10 pm

fless1 wrote:easy to install myself?

If you feel comfortable doing pads yourself (and/or have done that before), swapping/testing the sensors is a walk in the park...

There's one sensor per axle (LH front, RH rear from memory), they're 'embedded' into the brake pad.
Basically, the sensor consists of two wires that act like a switch when the wire insulation wears off with pad wear.
You can test sensor wear or malfunction by disconnecting the sensor: just follow the wire from the caliper and you'll find the plastic connector that hooks it up to the wiring loom. Disconnecting the sensor (again: from memory) suppresses any 'pads worn' signal from the sensor.

This google search retrieves some pics that may be helpful: https://www.google.co.uk/search?q=xj40+ ... ear+sensor

the daily: 01 S8 D2 http://bit.ly/2kIwP4m
the eyecatcher: 93 HFM 4.0 Insignia http://bit.ly/1iGrmsU
the GT: 89 JFJ XJS http://bit.ly/1WQGpC5
the problem child: 95 HFB X306 http://bit.ly/1cW11DN
the pocket rocket: 97 2.8 E36/7 http://bit.ly/12IfE7B
the ex-daily: MY94 BRG 3.2 http://bit.ly/14GTNrq

fless1
Posts: 180
Joined: Tue Jun 07, 2011 8:27 am
Location: Essex

Re: Brake Pressure Light

Postby fless1 » Thu Feb 01, 2018 4:18 pm

don't think issues could be caused by brake pressure switch problems ? Or can this not be case as getting plenty pressure (39 pedal pushed before hardening up)
'94 XJ40 - VIN 703709

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