Disco 2 3 Amigos and slight brake squeal.

NPG said:

Under normal braking conditions and without the 3 Amigos, it is hard to detect when EBD activates but it does and acts as a brake fluid pressure regulator.

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You'll definitely feel the EBD when it rarely kicks in cos it's even more pulsating than he ABS but in most cases you dont know if it's ABS or EBD ... believe me i've digged into this system untill it's deepest guts and i tell you that in normal braking mode when there are no conditions for any electronic involvment the brakes are purely hydraulic from the pedal and the modulator acts as a simple pipe

So this is like an old fashioned brake limiter valve, only more sophisticated.
I drive very gently on my brakes and have only felt ABS or EBD working when I have deliberately pushed it to work like that, just to check it is there.

HOWEVER, I have felt Traction Control working, when I didn't expect it at all. Was surprised: dry tarmac, slow speed, no apparent need. No problem, and no amigo came on other than the one that you would expect and it went off again once it had done its stuff, as expected.

As for HDC, I have yet to use it. You have to understand I am so old skool the idea of letting a computer and an engine take control of a vehicle containing me and my wife, on a steep and slippery hill, makes me sh1t myself. Not the way I was trained to go down that sort of slope off road, in an old 110 V8! That I am confident in doing!

One day, on my own, in a place I know, I must have a go. I hope to be pleasantly surprised!

(Must google "Canbus"! Haven't done my homework yet!)

Thank you for all of your input, funnily enough the pressure washer has had zero effect . I hasten to add that it wasnt on this forum that I read about brake dust being a cause, it was justified by the poster by saying that the squeal (vibration) can cause the sensor to detect fault, however, thinking about it I was just being super optimistic Next step is going to be diagnostics, I dont suppose there is anyone on here in the south wales area that may be able to assist in return for beer/cake ?

sierrafery said:

You'll definitely feel the EBD when it rarely kicks in cos it's even more pulsating than he ABS but in most cases you dont know if it's ABS or EBD ...

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What you describe sounds very much like the ABS pump kicking in, in which case it cannot be the EBD as the pump stays at rest -

sierrafery said:

in normal braking mode when there are no conditions for any electronic involvment the brakes are purely hydraulic from the pedal and the modulator acts as a simple pipe

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This is expected as all ABS modulators are fail safe (inlet valves open and outlet valves closed) to maintain the use of conventional braking in the event that the modulator becomes inoperable. What I tried to say in post #18 is that suppose we don't have EBD because of the 3 Amigos - there is nothing to counteract the increased inertial forces on the front brakes caused by the weight transfer upon braking. For a forward moving vehicle, this could result in a slight loss of traction on the rear wheels, in which case the braking force at the rear cannot be entirely applied to the road surface. Thus the rear of the vehicle would be moving faster than the front and hence the additional clamping force required on the front wheels to bring the vehicle to a complete stop, which might have been the cause of the squealing.

Stanleysteamer said:

So this is like an old fashioned brake limiter valve, only more sophisticated.

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Spot on. I think they used to call it load conscious regulating valve and unlike EBD, it was installed only on the rear axle.

Stanleysteamer said:

As for HDC, I have yet to use it. You have to understand I am so old skool the idea of letting a computer and an engine take control of a vehicle containing me and my wife, on a steep and slippery hill, makes me sh1t myself.

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If you dont like it you can use the pedal cos it overrides the electronic mode

NPG said:

What you describe sounds very much like the ABS pump kicking in, in which case it cannot be the EBD as the pump stays at rest -

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I attached the description from RAVE while your's looks like from the Technical academy...in this case from my experience i sustain what RAVE sais cos i made tests for all the default modes and for Return pump or relay fault the defaut is: ABS: Disabled.ETC: Disabled.EBD: Partly disabled. HDC: Disabled. So i remved the relay, got the 3 amigos then made some drive tests on slippery ground especially to see how the EBD works and even partly disabled(which means that just the deceleration threshold is increased) i felt the pulsing and stiffening of pedal exactly like it's described in RAVE

NPG said:

Spot on. I think they used to call it load conscious regulating valve and unlike EBD, it was installed only on the rear axle.

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On kit cars which have to use conventional brake gear from a donor, peeps often install variable brake limiters bought from somewhere like Europa and then set them up by whacking up and down a flat straight road with a mate watching closely who will tell you which set of wheels locked up first, until the adjustment is right. Very old skool! But the brakes were always more powerful than when on the donor as the donor nearly always weighed more. Frinstance, my Marlin roadster weighs something like 715 kgs, but the servo brakes are fitted as standard from the donor Morris Marina TC! To be honest, if you panic brake the wheels always lock up! Good thing they have tons of width! One day I'll remove the servo, to make them less fierce. Part of the reason I tend to be very soft on brakes, as well as not liking using fuel, tyres and changing brake pads and discs too often. Reading the road and the traffic, anticipation it used to be called, makes for such a smoother ride!

sierrafery said:

So i remved the relay, got the 3 amigos then made some drive tests on slippery ground especially to see how the EBD works and even partly disabled(which means that just the deceleration threshold is increased) i felt the pulsing and stiffening of pedal exactly like it's described in RAVE

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I do not doubt the reliability of your tests although I will be cautious with the interpretation of the results, given that the ABS unit was operating under fault state conditions, using an emergency braking strategy. In particular, if you had subjected the vehicle to test scenarios where the ABS and not EBD would have been applied under normal conditions, SLABS might decide to open and close the inlet and outlet valves in quick succession and use the force applied on the pedal to sustain fluid pressure in the absence of the pump. This is of course theoretical as I have no details of the backup strategies stored on the SLABS and therefore I am in no position to say exactly how the brakes behave when the modulator's functionality is reduced. The least we can expect is conventional braking, which I'm pretty sure is SLABS bare-bones strategy when everything else fails.

NPG said:

This is of course theoretical as I have no details of the backup strategies stored on the SLABS and therefore I am in no position to say exactly how the brakes behave when the modulator's functionality is reduced.

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IMO the modulator behaves quite the same once EBD kicks in cos it's about opening/closing valves just that on default there are other limits when the SLABS activates it. As i said even "partly disabled" i felt it in the pedal exacly like it's described in RAVE and i was sure it can be only the EBD as without relay the ABS was disabled hence my test with relay removed... it confirmed also that on ''solid" open circuit all the 4 warnings were on as they always should be according to the protocol(but we know how it works in other cases)