Chrisjameswild Posted August 1, 2013 Share Posted August 1, 2013 ABS problems - I need your help please! I have been restoring a 94 Vogue SE over the last 12 months and have hit a brick wall. All work completed and booked in for MOT and on the way the brakes started sticking on. The garage were stumped, I was stumped. It is certainly not the calipers as they have been rebuilt. It is not the booster unit as I have replaced it with a second hand unit. I have re-bled the system and...... the problem is back. The pump is not running constantly and there are no lights on the dash. Perhaps it is the pressure switch or a valve, all I know is that something is putting the brakes on and it is not me! Any ideas, where can I start (again)...... Thanks all, Chris Quote Link to comment Share on other sites More sharing options...
Josh NZ Posted August 2, 2013 Share Posted August 2, 2013 Give this a read, especially the last few pages. There's a lot of mention of ABS and pressure switch issues and you could stumble across something! http://forums.lr4x4.com/index.php?showtopic=69483&page=17#entry728757 I have no idea about rangies sorry, but that thread made me think of this one! Quote Link to comment Share on other sites More sharing options...
task Posted August 2, 2013 Share Posted August 2, 2013 Are the lights on the dash behaving correctly? Have you plugged the ABS ECU into testbook or similar and looked for fault codes? It should also show you valves sticking or opening when they shouldn't be. Quote Link to comment Share on other sites More sharing options...
duncmc Posted August 3, 2013 Share Posted August 3, 2013 I agree with Task. I would first check if there are any faults registered on the ecu first. I have a sneaky feeling that you can still do the blink test on a 94 Classic. I have the book "getting comfortable with wabco abs brakes range rover 1990 to 2002". They say that they have never seen a modulator block fail, however the book was written in 2008 even though it was updated in 2011. It was published in Arizona where things don't quite work the same....its a lot lot drier to start with. And moisture in the brake system is the killer.......I would put money on the replacement ABS modulator block having a sticky valve in it somewhere. Basically all the pressure valve on the pump does is control when the pump runs, and switch some lights as the appropriate pressures are reached. It sounds like you have pressure in the system, and it is rising and falling as it should do normally so the pump is cycling on and off as it should. It is only the valves within the modulator that then direct that fluid pressure to the correct circuit to apply the brakes.......so something has stuck within the block I am afraid.....a bit like how my pressure switch stuck the other week. The only other thing that it possibly could be is a faulty ABS ECU....but again they are meant to be reliable. The ECU sends an electronic signal to those valves within the modulator and if it is sending an incorrect signal......the same end result will apply. Therefore it is possible that there is a faulty wire somewhere, but who knows where or which one. I would bet on a faulty modulator valve. Quote Link to comment Share on other sites More sharing options...
task Posted August 4, 2013 Share Posted August 4, 2013 I've had two faulty ABS ECU's over the years, one refused to extinguish the dash lights but the other produced a dangerous fault where the ABS would kick in for all 4 wheels below 15mph every time you slowed down. That was a twitchy moment. Quote Link to comment Share on other sites More sharing options...
Chrisjameswild Posted August 5, 2013 Author Share Posted August 5, 2013 Thanks for your help. When I bled the modulator the fluid was contaminated so it sounds like it may be a dud. So frustrating to be thwarted at the last minute by an expensive-hard-to-get part! I have a spare ABS pump now so I will swap it over and give it a try, if only to rule it out. After this I guess a new ECU is another cheap try...... Anything to avoid changing that modulator again, it's a horror of a job. Quote Link to comment Share on other sites More sharing options...
duncmc Posted August 9, 2013 Share Posted August 9, 2013 I know what you mean about changing the modulator block. I have been there and done that. Quote Link to comment Share on other sites More sharing options...
coachman Posted August 12, 2013 Share Posted August 12, 2013 why did you change the block ,were there obviouss reasons,or a sequence of events. coachmaan . Quote Link to comment Share on other sites More sharing options...
duncmc Posted August 12, 2013 Share Posted August 12, 2013 why did you change the block ,were there obviouss reasons,or a sequence of events. coachmaan . I changed mine because it was leaking brake fluid into the footwell from the "master cylinder actuator rod" seal. I also upgraded mine to an ETC block whilst at it. The other night I found a thread on rangerovers.net where someone says he dismantled the modulator block and fixed some sticky valves as well as the electronics. Look for "brake booster rod adjustment" in the classic range rover section of the forum. I have asked for more details, but there is no reply as yet. Quote Link to comment Share on other sites More sharing options...
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