Range Rovers Forum banner

Sinking Pedal and ABS Module Bleeding

27K views 40 replies 13 participants last post by  1937prp9391 
#1 ·
Hi,

I changed the brakes all round on my 2005 Range Rover Sport 4.2 SC RHD. All parts moving freely on the brakes, no binding. Recently purchased so don't have a good baseline on the brake feel.

After bleeding I get a solid pedal when engine is off but once the engine is running the pedal sinks slowly down to the floor. If I hit the brake like in an emergency the pedal goes hard and starts sinking slowly making it harder to stop. After some driving in the car park the pedal will become softer and have a lot of travel. Hitting the brakes at this point still causes it to go hard but normal braking pressure will allow it to brake and stop ok but I still get full travel.

I have no external fluid leaks, the pedal goes to the floor so in 20 pumps like this I would drain the fluid and this isn't happening the fluid doesn't change at all.

I manually bled the ABS module by following the directions of a technician on here of cracking the connectors on the top of the ABS module while someone held the pedal and re-tightening but that didnt help. Servo is new and holding vacuum. Thought it may be an internal master cylinder leak even though it wasn't doing it with the engine off so I have replaced that with a new one, fully bled, still the same.

I thought I should do a proper ABS bleed so got it on SDD and followed the ABS Bleed procedure where the system got me to open the bleed nipples on each wheel and pump the brakes while it did its thing. It told me to do them in the order

Rear Left. Took around 30 seconds and there was no ABS Pump or Solenoid activation. Fluid flowed whole time.
Front Left. Took around 30 seconds and there was no ABS Pump or Solenoid activation. Fluid flowed whole time.
Rear Right. Took a couple of minutes and had a lot of ABS Pump and Solenoid activation. Pedal went solid for some of this one, no fluid flow.
Front Right. Took a while and had a lot of ABS Pump and Solenoid activation. Fluid flowed whole time, sometimes slower than others.

I did this twice with the same results and Its still doing the same thing so my question is should the procedure pulse the solenoids and pump for each corner or does the above sound correct? Having replaced the servo and master cylinder I'm suspecting the ABS unit as I'm not losing fluid and its the only thing I can think would be allowing the M/C to do a full stroke at this point.

Cheers
Stot
 
See less See more
#34 ·
Hi. Sorry I missed these replies.

No I haven't found the issue, the new hubs didnt help with the brakes. What I ended up doing which helped a bit especially for maneuvering was fit a pressure switch in line with the booster vacuum and have it turn on the aux vacuum pump when the pressure in the booster was too low.

The booster and I think master cylinder is different on the SC/Brembo cars and I still wonder if the aftermarket parts I have are not the right ones still even though I bought them as such. Its as if there's just not enough volume in the booster to press the master cylinder the distance it needs to go to fully apply the brakes. I was looking into whether I could source a big bore M/C even, the standard one is 21mm on the rear circuit and 27mm front circuit.

Cheers
Stot
 
#35 ·
I too am following thread as I have a 2011 sport SC with Brembo on front. In August I had to tow a boat of about !800lbs(small inboard ski boat, no trailer brakes) and the next day found brake fluid exiting about midway from rear lines and pedal soft and low. I did not notice the failure while towing and did not have any panic stops. I drove it to my local goto independent shop where they replaced the rear hard lines attached to the frame and reasoned the line had corroded through. The shop then bled the system the hard way with short pedal strokes (each wheel is over 20 reps multiple times) only to find a soft pedal each time. My shop guy finally threw his hands up and wanted to start throwing parts at it. It now had brakes again but a soft pedal and nothing like the stopping power before. I had a LR3 previously and no comparison to the Brembo fitted sport brakes. We agreed for me to take it back as I am retired now but have worked on vehicles since the 60's and have diagnosed many problems but nothing like this...

I have now pressure bled all 4 wheels twice. Then acquired a abs auto bleed from Autel.and bled while running the program several times. In doing Autel bleed the first it directs to is left rear which shows program running but no pump activation and the dash screen shows EBD fault. The fault is not stored in either vehicle system or the Autel. Dynamic stability control is part of the system and gets input from wheel speed sensor, yaw sensor, and steering angle sensor. None of this shows any faults.

My question because I am a little lost at the moment, did you see a EBD fault(Electric brake-force distribution) on the left side wheels when the pump did not activate? It would have shown on the instrument panel.

Any feedback would be appreciated.

2011 Sport SC, 2006 LR3, 2012 Volkswagen Beetle 2.5, 1969 TR6
 
#36 ·
I too am following thread as I have a 2011 sport SC with Brembo on front. In August I had to tow a boat of about !800lbs(small inboard ski boat, no trailer brakes) and the next day found brake fluid exiting about midway from rear lines and pedal soft and low. I did not notice the failure while towing and did not have any panic stops. I drove it to my local goto independent shop where they replaced the rear hard lines attached to the frame and reasoned the line had corroded through. The shop then bled the system the hard way with short pedal strokes (each wheel is over 20 reps multiple times) only to find a soft pedal each time. My shop guy finally threw his hands up and wanted to start throwing parts at it. It now had brakes again but a soft pedal and nothing like the stopping power before. I had a LR3 previously and no comparison to the Brembo fitted sport brakes. We agreed for me to take it back as I am retired now but have worked on vehicles since the 60's and have diagnosed many problems but nothing like this...

I have now pressure bled all 4 wheels twice. Then acquired a abs auto bleed from Autel.and bled while running the program several times. In doing Autel bleed the first it directs to is left rear which shows program running but no pump activation and the dash screen shows EBD fault. The fault is not stored in either vehicle system or the Autel. Dynamic stability control is part of the system and gets input from wheel speed sensor, yaw sensor, and steering angle sensor. None of this shows any faults.

My question because I am a little lost at the moment, did you see a EBD fault(Electric brake-force distribution) on the left side wheels when the pump did not activate? It would have shown on the instrument panel.

Any feedback would be appreciated.

2011 Sport SC, 2006 LR3, 2012 Volkswagen Beetle 2.5, 1969 TR6
Hi,

I did change my rear hard lines and all 4 flexis too.

I have no brake fault codes at all. I have monitored the brake pressure and as the pedal goes down the brake pressure continues to go up until the pedal is all the way down. No variation, holds its pressure fine.

To me it feels like the vacuum reservoir just isn't big enough. I press the pedal and it uses up the pressure in the booster in the first inch or so of pedal and as I hold the pedal the engine vacuum lets the pedal go down slowly till it stops.

Cheers
Stot
 
#37 ·
Well, I do not know what has changed after the line break to rear and repair but even though this 2011 sport has brakes, the pedal is way lower then before. With the big Brembo calipers up front, the vehicle would stop on a dime with just a tap on the pedal. That does not exist currently.

The ABS bleed was done at my independent shop and he said that it (the abs bleed program) worked fine. Then I used a cheap Autel version with dongle and iphone and have bled twice with results like you had where only 2 right side wheels would activate and the left side 2 would not activate ABS pump. I am waiting now on a more expensive icarsoft scan tool with cable and will try that computer bleed. There are still no codes or lights while driving and soft pedal. Only EBD fault briefly on dash screen while performing ABS bleed on the 2 left side wheels that did not activate. The fault did not store or stay lit after moving on to next wheel.

My feeling is something besides air is complicating because of the amount of inputs the system sees...Wheel speed, steering angle, yaw/accelerometer, active stabilizaton/damping, ride and handling optimization, abs module, brake switch, all play a roll.

I will post next results soon. Thanks for response.
 
#40 ·
I’ve read all this, but have you replaced the booster? Just curious. I know you replaced the rear lines, the six flex pipes, hubs, rotors, pads, ABS unit, and master cylinder. Possibly front caliper rebuild, too. I don’t recall reading about the booster or vacuum pump.
 
Top