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Discussion Starter · #1 ·
On my 2000 D2, I've changed all 4 calipers, Wagner thermo quiet ceramic pads, rotors, steel flex hoses, and still have a crappy pedal, I changed the booster to an 04 booster, changed the shuttle valve switch, and replaced the master cylinder with a new one, bled it with a scan tool etc, first time I went driving, all the brakes got stuck on, pulled the master and adjusted the rod, and kept doing trial and error until I got a good feeling pedal (well a tolerable pedal) Its been OK for a while, but still just not the best brake pedal, no where near the braking power in my P38, can't lock them up, even on dirt cant get it to lock a wheel and activate ABS or slide. Yesterday, out off roading, I was doing a lot of sitting spinning tires working the TC, and for a while the brake pedal completely changed, fantastic brakes, locked up on a dime on the trail, great feeling pedal, like a proper boosted brake pedal like in my pickup truck. After that the brakes got stuck on again out on the trail, pulled the master (in the woods), adjusted the rod back, drove back to my friends shop and re bled with a scan tool, now they are working but not great again, pedal has a lot of travel before it starts stopping. For the life of me I can't figure this out. It seems like the brakes are better at highway speeds and RPM, city driving, a panic stop is just not an option. The just have no bite. My father had a 03 disco that stopped like a BMW,. Any help is appreciated.

Thanks
 

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Might be an air lock in the modulator though, that's why the brakes were improved after TC operation, you have to pedal bleed it first in the correct sequence(from short to longer lines) then power bleed it with tester, the pedal bleed will push out the air ONLY from the lines between the master cylinder and calipers through the N/O inlet valve circuits of modulator and the power bleed will push out the air ONLY between the return pump and the N/C outlet valve circuit...if you've bled it only with tester there might be air locked between the non return valves and the return pump in the modulator... after bleeding it find a slope and make the HDC work as much as you can, that will clear the modulator of air for good then pedal bleed it for a last time... then it should be good IMO, btw don't mess with the master cylinder's rod

that flow with red and blue is activated both sides on pedal only and the rest is steady the on power bleed the fluid is pushed downwards between 8 through 9 and 11 ... that's why the corrsct sequence and both (pedal and power) bleedings are important if the system was empty
 

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Discussion Starter · #3 ·
When I first installed the new master cyl, the brakes would apply themselves and get stuck on. Do you think that was because of air in the system or different clearances in the new master? I did a bunch of manual pedal bleeds then at least 10 modulator cycles with the scanner then a power bleed. Im using Dot3/4 fluid as that was all that was available when I changed the master. It seems like the brakes got stuck on yesterday when the system got hot?
 

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I edited my message while you was writing to make you understand what's in there... did you pedal bleed it in the correct sequence and as in the book with bleed tube attached?... then also the correct order on power bleed? the sequence for LHD is: front RH - front LH - rear RH - rear LH ... when the system was empty everything must be done correctly cos air locks can be very 'stubborn' ...happened to me, so if you misssed something do it again correctly
 

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BTW, just remembered, replace the return pump relay(R10 enguine bay fusebox) to rule it out cos there is a technical bulletin about sticking relay which can cause such problems
 

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Discussion Starter · #6 ·
Ill have to give it another go, do you think that the first time I bled it and the brakes stuck on it was because of air in the system though? I would like to have that rod set to the correct length...
 

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there's no reason to mess with the cylinder rod whatsoever, it's factory set to proper position i doubtb that it was the root of the problem it's very possible that air in the system to make you such tricks, happened to me too... though rule out that relay too, at least swap it with R8(heated screen) for test
 

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Discussion Starter · #8 ·
Ill swap the relay, I'm going to have to find one the factory length of the rod is as I stupidly didn't measure it when before I adjusted it. Maybe I got a bad master cylinder? I just dont under stand what would make the truck apply all the brakes like that. the only way to make it home when that happend was to crack the lines on the master and they would release.
 

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Discussion Starter · #10 ·
Ill try it but I doubt it is that, as there are no warning lamps, bells etc. The brakes staying applied seemed like the rod was not allowing the master to fully release
 

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I edited my message while you was writing to make you understand what's in there... did you pedal bleed it in the correct sequence and as in the book with bleed tube attached?... then also the correct order on power bleed? the sequence for LHD is: front RH - front LH - rear RH - rear LH ... when the system was empty everything must be done correctly cos air locks can be very 'stubborn' ...happened to me, so if you misssed something do it again correctly
Incorrect. This is one of the more glaring mistakes in RAVE. The Disco brakes bleed like any other. RR, LR, RF, LF.
 

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And why is that so? ... IMO it's very logical what RAVE sais cos the correct procedure is to bleed starting ftom the shortest line and ending with the longest, this has a certain technical logic too, what's the logic(technical benefit) of the procedure described by you please?
 
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