P38 brakes or lack of them!

[barny]

Bit confused with this one as our p38 4.6hse has now got a longish spongyish pedal that intermittantly rectifies itself. When we first got the car it had a great pedal but the brakes where a little dull sometimes needing a bit more effort than was needed, but we accepted that as being a feature of the car.

Anyhoo on sat the brakes failed and needed a damn hard shove to stop with a fairly long pedal. Quick google and found out the odd buzzing noise behind the dash was actualy the ABS PUMP repressurising the the Pressure Accumulator(this often happened since owning the car but didnt know what it was ) and came to the conclusion this was goosed. fitted a new one and after several attempts of pumping the brakes to get it up to pressure eventually we had a storming pedal and brakes that worked really really well. Went home and all was well till we tried it this mornin and its back to square one

Anyone got any ideas ? My nxt thought is to bleed the brakes as i asumed the pump would self bleed the system. The dash lights are the abs,TC and brakes light up.

[muddysteve]

did you change the pump or the accumulator? i think the pump should run every third brake application and for about 3 seconds. if its running more than that the accumulator is the usual suspect

try over on rangerovers.net forum, loads of p38 info there

[Rossko]

If you changed the pump without bleeding, now is the time to bleed.
There's an elaborate sequence to go through, might as well do the whole thing and so get fresh fluid throughout.

If that doesn't sort it, possibly the accumulator or pressure switch duff.

[barny]

Sorry i didnt make it clear, i replaced the Accumlator as it was the cheaper part and the pump at the time was working.

Ive now since bled the system through but the typical "furthest from the master cylinder route" - im now aware of the elaborate bleeding routine and will do that later as ....... now the pump no worky! To gain access to the pump I've removed the fuse box + siren and have checked the wiring to the pressure sensor. I've no wiring diagrams (so i dont know what i should be seeing )as yet* but i had 2 live feeds to the switch and no "apparent" feed to the pumps motor. I'll not jump to any conclusions as yet.

Thanks for your help also the link to the code reading on the other thread   :D

*Nice landrover Numpty "specialists" are getting them to me in the morning

[Rossko]

If you are going to poke around this, it will be well worth while to get the manual with diagrams, procedures etc e.g. RAVE disc

[Range Rover Blues]

I went through 3 litres of fluid replacing the pipes and bleeding the similar RRC ABS system, it is quite complicated and often frustrating to do.

[barny]

I Dont think its a brake bleeding issue, if so then that'll come later. I just need to find out whats not making the pump run.

I can bridge the pump relay and the pump will work, but i cant see from the diagrams what controls the relay. It could either be the pressure control switch, the abs ecu or the BECM  :shock:

Its starting to really [throw it] me off now, the local landy specialist will "look" at it for

[Rossko]

I can bridge the pump relay and the pump will work, but i cant see from the diagrams what controls the relay. It could either be the pressure control switch, the abs ecu or the BECM

Nowt to do with BECM.

If the pump or relay was duff, you should get an ABS fault light due to not recovering pressure when asked.  No light? (Does the light work at switch on, and go away after a short drive?)  That would suggest the pressure switch isn't calling the pump - it thinks pressure is good already.

I think the pressure switch is a dual affair, with both 'high' and 'low' pressure contacts, but have no wiring diagram to hand.

Have you read this?
http://www.rangerovers.net/repairdetails/braketc/abs.html
One of the interesting things it points out is that hard brake pedal probably indicates faulty pump/acc system
I reckon your mushy pedal was a properly working power system coping with poor fluid / bubbles / worn pads / mushy flexibles?  If the pump had to work overtime to cope with it, you may now have a worn pump/burnt switch/burnt relay - plus the original mushy problem still lurking.

I keep hearing about this RAVE thingy but not really sure what it is? Any links or info Gladly recieved  :)

http://lmgtfy.com/?q=land+rover+rave+disc
Seriously, it is worth having