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2006-2009 Range Rover Sport
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Discussion Starter · #21 ·
Hi Again,

I was trying to diagnose the pedal going hard when quick braking and I have a feeling that although my servo is fine, and the pipework is all intact with working check valves, that there might not be enough vacuum. When i stamp the brake it goes hard and then starts sinking while applying the brake, like the manifold is suck suck suck suck.

There is an aux vacuum pump on the SC motor and if I jump the relay it runs but I don't think its running at other times. I think for example that when I cold start and idle up/choke is active it should be running.

Anyone know if the activation of this can be data-logged in SDD? I cant find it anywhere.

Cheers
Stot
 

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Discussion Starter · #22 ·
Hi,

I'm still chasing this. I made up some 'blank replacement calipers' on the lathe ( solid block with a banjo bolt hole so the fluid cant go anywhere ) and put them on in place of the Brembos at the front and the pedal doesn't sink so lines are all off the hook now. Pretty sure the pads in the Brembos are not retracting too far as the car will not move until the pedal is almost all the way up so the pads are still grabbing the disc early in the pedal stroke, bite point doesn't change after the sinking. Pedal can still sink all the way down at this point. Have bled them multiple times, theres not really anywhere for air to be trapped at the actual caliper as the bleed nipple is literally at the top of the cavity.

I cant see any leaks on the Brembos, maybe a seal has moved and is compressing in a weird way or something but Ill probably get a seal/piston kit and strip them down to inspect and revive.

Cheers
Stot
 

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2006-2009 Range Rover Sport
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Can you narrow it down further to right front or left front? Curious if it is just one side or both. Either way good trouble shooting.
 

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You are going around and around in circles and not getting anywhere - just take to someone who knows what they are doing.
 

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You are going around and around in circles and not getting anywhere - just take to someone who knows what they are doing.
I don’t know that he has not been going anywhere. He has now isolated the problem to the front calipers. I’ve got the same issue, so I am following all his efforts with much interest.

I for one appreciate his persistence.


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Discussion Starter · #26 ·
Hi,

Its a fair point but I have worked on cars all my life, built a couple from scratch too so I'm happy doing the diagnosis myself. I think a shop would have done a lot of the same diagnosis and replaced the same parts I have if I'm honest so I would have just been paying someone else to do that and probably a premium on the parts too. If I exhaust my options then Ill take it somewhere. ;)

I haven't done anything with the calipers yet but have had time to think about it as ive been travelling and I believe I have narrowed it down to the calipers, or the hubs. I think someone already mentioned hubs in this thread to be fair.

I think the hubs are more likely for the symptoms especially now that I have replaced other parts. I think that the brembos being solid mounted to the steering knuckle make the symptoms of worn hubs on the brakes different than regular slide pin mounted calipers which can follow the disc more.

I need to find my magnetic dial indicator to test this but I think if the hubs are worn the weight of the truck on the wheels is causing the wheels and so discs to sit at a slight angle. / \

When I apply brakes the pads start to bite and then further pressure in the system starts to straighten up the wheels, hence the sinking pedal as the slack in the hubs is taken up and wheels straighten up in line with the calipers. | |

When I let go the wheels settle back to / \

With brembo 4 pots this will push the pistons back into the caliper each time even with the smallest amount of play and it would take a fair amount of fluid to push them back again each time. With regular calipers the slide pins will allow an amount of flex that may just ride with this and not really be noticeable until the hubs are really bad.

Ill check the hubs more closely and If I can find my dial indicator I can test this a bit more scientifically than giving the wheels a wobble.

Cheers
Stot
 

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Just by coincidence I had my front wheel jacked up and for some forgotten reason I wobbled it and decided the hub was no good. I had not really noticed this when driving the car. I also noticed when I replaced the hub that my long brake pedal seemed to improve. Not sure if it was imagination but I thought like you that the wobble would certainly open the calipers.
 

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Discussion Starter · #28 ·
Thanks Arby, I think you are right here.

I jacked up the front of the car so both wheels were off the ground and gave a wiggle. Definitely a little play in both sides, one more than the other. If I put my fingers in the gap between the caliper and the disc I can feel the movement easily as I wobble the wheel. Also the discs have coloration suggesting they are only biting around the edges more than the center.

Product Metal Tire Steel Automotive tire

I have ordered new hubs as its clear they need doing so fingers crossed that will sort out my sinking brake too.

Cheers
Stot
 

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Thanks Arby, I think you are right here.

I jacked up the front of the car so both wheels were off the ground and gave a wiggle. Definitely a little play in both sides, one more than the other. If I put my fingers in the gap between the caliper and the disc I can feel the movement easily as I wobble the wheel. Also the discs have coloration suggesting they are only biting around the edges more than the center.

View attachment 267688

I have ordered new hubs as its clear they need doing so fingers crossed that will sort out my sinking brake too.

Cheers
Stot
I am curious if this poster has found that replacing the hubs solved his issue.
 

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Just jack up the front wheels and try wiggling them. Especially at 12 and six. 3 and 9 could be a loose tie rod end and not affect the brakes. The front hub on the other side of my car went a while back and there came the low brake pedal again so for sure a worn hub bearing causes a long brake pedal.
 

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It's the rears at issue, and I detected no noticeable play.
 

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I have ordered new hubs as its clear they need doing so fingers crossed that will sort out my sinking brake too.
Stot, please kindly confirm the issue has been solved.

I'm having the exact same symptoms on a 2012 Disco 4 with only 130kkm on it. I don't really think anything could happen to ABS/Master Cylinder on a fairly fresh velicle. Flushed brakes two times with ABS engagement, all the lines look good. It stops fairly well, but the pedal doesn't feel right, it just goes down when you press it hard enough.
 

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Stot, please kindly confirm the issue has been solved.

I'm having the exact same symptoms on a 2012 Disco 4 with only 130kkm on it. I don't really think anything could happen to ABS/Master Cylinder on a fairly fresh velicle. Flushed brakes two times with ABS engagement, all the lines look good. It stops fairly well, but the pedal doesn't feel right, it just goes down when you press it hard enough.
I now have acquired this issue as well.

I've been noticing - for months now - what I consider excessive brake dust on my fronts, particularly front left.

I wonder if the hub is failing, and causing excessive wear, and excessive brake pedal travel - because that's what I'm getting. Uncomfortably long travel before the brakes bite.
 

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Discussion Starter · #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
 

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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
 

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Discussion Starter · #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
 

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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.
 
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