21 Turbo 21 turbo braking system

[plvehicles]

well after finally getting the car back on the ramp I had a mass effort to get the brakes sorted, ive renewed all calipers, discs, pads flexi lines and copper ones, and bled it all up.
but here is my problem, it seems like there is no servo assistance( I know it doesn't have a conventional vac servo by the looks of it) but how does the system work?????
the brakes work but have a really hard pedal with no travel, is it all governed by the abs unit??? and what is the motor/pump unit under the header tank as that was unplugged
cheers
pete

 

[Haz]

Bleed up is explained in the Hayes, fronts are traditional way, rear is primed with the pump, the unit under the header tank.
The pump can go faulty, and the rear compensator valve

 

[Andyquadra]

is there a buzzing noise from under the heater tank after you turn the ignition on?

 

[plvehicles]

haz ive bled the system completely and have put it on brake rollers to see each wheels braking force, and the all come up, its just that I have a rock hard pedal, rear compensator is ok as I ve stripped cleaned and rebuilt it. im just wondering if ive got a partially seized master cylinder or the abs unit is faulty in some way???

andy.... nope no buzzing from the pump unit???

does anyone have a wiring diagram so I can trace what power is where
thanks

 

[Haz]

The buzzing is the abs pump priming the system, well filling the sphere up. There's a pressure valve to turn it off.
If it's unplugged it may be due to it constantly running, a fault with either.
Iirc the 2 relays under the ecu, one is for the pump, and there's a chunky live wire from battery to pump too.

 

[DaveL485]

andy.... nope no buzzing from the pump unit???

The 21 system isnt a traditional system. There isnt a servo, its a full electronic assist system. There is an accumulator unit on the pax side under the expansion tank, its a pump with a big black ball sat on top of it. The pump consumes fluid from the brake reservoir and pressurises it into the black ball. It turns on when the pressure drops below 1600psi, and turns off when the pressure hits 2150psi. It uses this pressure store as the "assist". Without it the pedal feels hard and spongy, much like a normal servo system without servo assist.

When the pump isnt working and pressure is low you should get both the ABS light and Handbrake lights permanently on. If you sit with the ign on and pump the brake pedal and get no buzzing from the pump, it's goosed. Check it has power. You can take it off and test it across a battery.

**BE CAREFUL because the feed is connected to the bottom of the res, and it'll empty the fluid everywhere if you dont close off the line**

**BE EVEN MORE CAREFUL because if there is pressure in the black ball its high pressure enough to inject the fluid under your skin when it escapes, and brake fluid is some nasty shit to take intravenously**

 

[DaveL485]

Oh and the pipes out of the bottom of the res perish over time. If you move it it may well just break up and howl fluid everywhere, its happened to me enough times.
Theyre not pressurised (the feed back in is though) so dont tend to break and leak unless disturbed. And its right above the exhaust.

 

[plvehicles]

cheers dave that's exactly what ive got with the hard pedal and no noise from the pump, will check the supply to it and see what ive got, the handbrake light is continuously on but not the abs light, and as it happens I have no abs either it just locks up, where is the pressure sensor which governs when the pump turns on and off?
I remember looking at the connectors of the pump unit and found a vw and ford stamps on the plug housings, does this mean the system was a mish mash of parts from the factory, or has someone f**ked about with it?

 

[DaveL485]

cheers dave that's exactly what ive got with the hard pedal and no noise from the pump, will check the supply to it and see what ive got, the handbrake light is continuously on but not the abs light, and as it happens I have no abs either it just locks up, where is the pressure sensor which governs when the pump turns on and off?
I remember looking at the connectors of the pump unit and found a vw and ford stamps on the plug housings, does this mean the system was a mish mash of parts from the factory, or has someone f**ked about with it?

It'll be original mate, there was never anything to cross it with until recently @Red21 found some stuff.

Does the ABS light ever come on at all? If not, the bulb will have been pulled to get it past MOT (or its just blown from being on all the time). Sounds like your pump has packed up anyway.

 

[plvehicles]

got the pump running today, after a while with the power probe I got ignition live to it and a good earth, so that's that bit out of the equation but it still hasn't given me a better (softer) pedal
what would be the average pedal travel from top to full hard on the brakes?

oh and how long should the pump run for and what governs when it turns on and off? as it seems to be running continuous( as in I left it 20 mins )and it was till running
sorry for all the questions but this is really beginning to bug me now
cheers
Pete

 

[andybond]

It turns on when the pressure drops below 1600psi, and turns off when the pressure hits 2150psi

@plvehicles

 

[DaveL485]

got the pump running today, after a while with the power probe I got ignition live to it and a good earth, so that's that bit out of the equation but it still hasn't given me a better (softer) pedal
what would be the average pedal travel from top to full hard on the brakes?

oh and how long should the pump run for and what governs when it turns on and off? as it seems to be running continuous( as in I left it 20 mins )and it was till running
sorry for all the questions but this is really beginning to bug me now
cheers
Pete

It should run, from empty, for 20-30 seconds, any more than a minute and something is wrong.

Continuous running isnt unheard of, it's probably goosed mate. Try another one if you can find one.... search for Land Rover Accumulator on eBay theyre VERY similar, though i've never tried retrofitting yet.

 

[Deleted member 486]

Just to hijack this thread!

Rusty memory is making me think that I saw somewhere the Quadra system is different again. Is this correct? If so, how is it different and what parts are common?

 

[DaveL485]

Just to hijack this thread!

Rusty memory is making me think that I saw somewhere the Quadra system is different again. Is this correct? If so, how is it different and what parts are common?

Yes Quadra system is different.

Common? Calipers, front flexis, front discs, all pads. Brake fluid. Er, front solid brake lines, front ABS sensors. The accumulator itself, but the bracket is different as it also holds the pneumatic diff lock controller.
Whole computer/wiring/master cylinder setup is different. Whole back setup is different save the calipers and pads.