2012 Range Rover Evoque brake system problem.
Discussion
I have an ongoing issue where air keeps getting into my braking system.
I have bled it numerous times and had a brand new LR master cylinder.
The pedal will stay firm for a week or so then starts to go soft.
Would brake lines or pistons seals be a good thing to change?
I have pressure bled and used the 2 person system.
Any ideas / previous experience??
I have bled it numerous times and had a brand new LR master cylinder.
The pedal will stay firm for a week or so then starts to go soft.
Would brake lines or pistons seals be a good thing to change?
I have pressure bled and used the 2 person system.
Any ideas / previous experience??
Dashnine said:
When you’re bleeding it, does any one caliper take more pumps of the pedal to get their air out? If so, there’s a leak on that circuit.
As I would expect the furthest caliper away from the reservoir has the most air in it. The opposite diagonal front caliper has minimal air.The reservoir always stays full with no signs of leakage anywhere.
All pads and disks have plenty of meat and the LHF caliper is new.
Jamie03M3 said:
Air is present at all calipers.
I'm not familiar with that braking system, but air getting into calipers is not normal. Calipers normally only see tidal flow so air would not usually be carried downhill to the calipers. Does that vehicle have any sort of recirculating ABS system that could be pulling air in?GreenV8S said:
Jamie03M3 said:
Air is present at all calipers.
I'm not familiar with that braking system, but air getting into calipers is not normal. Calipers normally only see tidal flow so air would not usually be carried downhill to the calipers. Does that vehicle have any sort of recirculating ABS system that could be pulling air in?Dashnine said:
So why write your comment:
Because it's true. It is not normal for air to get into the calipers after they have been filled and bled. GreenV8S said:
air getting into calipers is not normal.
Either the bleed nipple is leaking, or the cylinder seals are leaking, or air is flowing through the pipes. None of those are common failures. An external leak that allows air in will almost certainly allow fluid out under the sort of pressures in a typical braking system. It is very unusual to have air flowing through brake lines because these usually only see relatively small amounts of tidal flow when the brakes are applied/released, and calipers tend to be quite low in the circuit relative to the brake master, proportioning valve and ABS system.
Either there is a mistake in the brake beeding process (air is being introduced and then bled out and it wasn't actually in the caliper prior to the bleeding) or something else is introducing air into the brake lines - and that would need to be quite close to the lowest point in the circuit due to the previously mentioned tidal flow and the fact that air will settle out upwards. A faulty ABS pump close to the calipers might do it, but that isn't common in my experience.
GreenV8S said:
Dashnine said:
So why write your comment:
Because it's true. It is not normal for air to get into the calipers after they have been filled and bled. GreenV8S said:
air getting into calipers is not normal.
Either the bleed nipple is leaking, or the cylinder seals are leaking, or air is flowing through the pipes. None of those are common failures. An external leak that allows air in will almost certainly allow fluid out under the sort of pressures in a typical braking system. It is very unusual to have air flowing through brake lines because these usually only see relatively small amounts of tidal flow when the brakes are applied/released, and calipers tend to be quite low in the circuit relative to the brake master, proportioning valve and ABS system.
Either there is a mistake in the brake beeding process (air is being introduced and then bled out and it wasn't actually in the caliper prior to the bleeding) or something else is introducing air into the brake lines - and that would need to be quite close to the lowest point in the circuit due to the previously mentioned tidal flow and the fact that air will settle out upwards. A faulty ABS pump close to the calipers might do it, but that isn't common in my experience.
Only now and again have i come across brakes that have proved difficult to bleed out, clamping the pistons or slave cylinders fully closed proved a cure.
At the very least eliminating calipers from fault might help here.
No doubt you've serviced the brakes fully re cleaning and lubing, ie nothing sticking all pistons free in their bores.
At the very least eliminating calipers from fault might help here.
No doubt you've serviced the brakes fully re cleaning and lubing, ie nothing sticking all pistons free in their bores.
GreenV8S said:
Dashnine said:
So why write your comment:
Because it's true. It is not normal for air to get into the calipers after they have been filled and bled. GreenV8S said:
air getting into calipers is not normal.
Either the bleed nipple is leaking, or the cylinder seals are leaking, or air is flowing through the pipes. None of those are common failures. An external leak that allows air in will almost certainly allow fluid out under the sort of pressures in a typical braking system. It is very unusual to have air flowing through brake lines because these usually only see relatively small amounts of tidal flow when the brakes are applied/released, and calipers tend to be quite low in the circuit relative to the brake master, proportioning valve and ABS system.
Either there is a mistake in the brake beeding process (air is being introduced and then bled out and it wasn't actually in the caliper prior to the bleeding) or something else is introducing air into the brake lines - and that would need to be quite close to the lowest point in the circuit due to the previously mentioned tidal flow and the fact that air will settle out upwards. A faulty ABS pump close to the calipers might do it, but that isn't common in my experience.
Interestingly I bled the car about 6 times tonight. Each time I braked hard to get the ABS pump working.
Every time I came back there was air bled from all wheel stations.
I was completely ruling out the ABS pump but after tonight I am seriously considering it as a fail point.
I opened and closed each nipple 5 times every time I bled. This was done for 6 different bleed sessions. Surely this would be enough to purge the air!
Smint said:
Only now and again have i come across brakes that have proved difficult to bleed out, clamping the pistons or slave cylinders fully closed proved a cure.
At the very least eliminating calipers from fault might help here.
No doubt you've serviced the brakes fully re cleaning and lubing, ie nothing sticking all pistons free in their bores.
Thanks for your reply!At the very least eliminating calipers from fault might help here.
No doubt you've serviced the brakes fully re cleaning and lubing, ie nothing sticking all pistons free in their bores.
Brakes were stripped, cleaned and lubed when I did the discs and pads. All bleed nipples were replaced as well.
The pistons are nice and smooth and easy to retract.
I may attempt the bleed with all calipers clamped but for air to be found at all wheel stations I am considering the ABS pump (after having 2 different master cylinders).
Jamie03M3 said:
Guys thanks for your replies.
To clarify I did mean air is present at all calipers when bleeding.
On reflection the air must becoming from a central point to arrive at all calipers.
Finding that point appears to be a real PITA.
This makes little sense when it will be totally independent lines from the ABS unit to each corner.To clarify I did mean air is present at all calipers when bleeding.
On reflection the air must becoming from a central point to arrive at all calipers.
Finding that point appears to be a real PITA.
And likely at least 2 independent lines from the master to the ABS unit, possibly more lines
So should be incredibly difficult for air to be shared among all.
What is the history with the vehicle ? How long have you owned it ? Has any brake work been done before this problem appeared ?
stevieturbo said:
Jamie03M3 said:
Guys thanks for your replies.
To clarify I did mean air is present at all calipers when bleeding.
On reflection the air must becoming from a central point to arrive at all calipers.
Finding that point appears to be a real PITA.
This makes little sense when it will be totally independent lines from the ABS unit to each corner.To clarify I did mean air is present at all calipers when bleeding.
On reflection the air must becoming from a central point to arrive at all calipers.
Finding that point appears to be a real PITA.
And likely at least 2 independent lines from the master to the ABS unit, possibly more lines
So should be incredibly difficult for air to be shared among all.
Your right it makes no sense at all lol.
The car was fine, we have had it since Feb 2020. The rear pads and discs were done in early 2021. This problem started early this year and started with an ever softening pedal. Master was changed. It firmed for a while then went soft again.
What is the history with the vehicle ? How long have you owned it ? Has any brake work been done before this problem appeared ?
fbwinston said:
if I remember correctly there is an option to bleed the abs module using a suitable diagnostic tool. Manual bleeding may not be sufficient.
this is true, some vehicles it is essential to do this.And if the system was allowed to run dry during any works....could well be the problem
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