Marcolandy

Marcolandy

Member
Hello Fellow Landy Guys,

I'm desperately looking for help/any kind of information regarding the following problem:
Brake pads have permanent contact with brake disc, more precise front left and rear right.
What has been done:
- 4 new calipers
- 4 new brake lines
- new brake pads
- new brake master cylinder

My Discovery was in 3 different workshops and the problem still exists. :-(

Appreciate to get any information, what could cause this brake problem.

Best Regards, Marco
 
Was the problem there before all of the changes ?
Is it both brake pads on each of the problem brakes or only 1 ?
If only 1 pad, it could be a sticking / misaligned caliper or caliper carrier.
If both, potentially pressure is being trapped in the brake system & not be released to the reservoir.
If you take a wheel off on each of the problem corners can you force the piston in so that fluid returns to the reservoir ?
If not, maybe the mastercylinder is faulty or the brake servo or brake pedal is stuck down.

PS I should have started with a different question : Do you have the ability to work on your own car ?
If not, you will have significant problems with this type of issue. It requires logical fault finding skills that any "good" garage should have (but many do not !). However, it could be expensive as it may require a lot of time to work through the potential causes.
Many garages lose interest in this type of problem because the believe the owner will not pay the full amount for all of the labour time involved.
 
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Did they replace the slide pins when they replaced the calipers as new calipers are no good without the slide pin kits being replaced as well. The new calipers will just stick if they didn't? Plus did they replace the flexi hoses or just metal brake pipes. Flexi hoses can delaminate internally and act as a one-way valve in the brake system making the brakes bind.
 
Interesting this as you did say you had replaced callipers and master cylinder.
I am going to make the slightly rash assumption that all the new parts were "good". and fitted properly, as @lynall mentioned this may need checking.

If you replaced the callipers, the guide pins should have been replaced at the same time. If not replace these or take them out and clean them up. I had one more or less rust into place, but once taken out and all the rust cleaned off it worked fine. Doubtful guide pins on opposite corners of the vehicle would go at the same time, but not impossible.

It is odd that 2 callipers are doing this. The chances of two flexi hoses delaminating at the same time same very low to me.
EDIT, I'm an idiot did not notice till now that you have replaced 4 brake lines. Did you mean flexis or the solid lines? If the solids than you can ignore the latter part of this post.:rolleyes::rolleyes::rolleyes::rolleyes::rolleyes:
I think the fault must lie in the pipes connecting the master cylinder to the two callipers, forming a one way valve.

I don't know because I have never had to investigate this, but they may connect into one somewhere? Saabs used to separate the dual braking system that way, but most manufacturers do it so one line is front brakes and the other is the rears.

Anyway, I'd follow all the brake lines back to the master cylinder, disconnect them from the flexis )and see if there is a blockage of some sort. A bit of a seal or something may have worked its way down from the old master cylinder, into the pipe(s) and be causing the problem.
If you can pump air or fluid in both directions, collecting the old fluid in a jar or something, you may see some offending material come out.

If it is this, it should be a relatively cheap fix. no longer any point in chucking money, by replacing parts, at the problem.

I suppose it is faintly possible that a pipe may have rusted internally and a shard of rust is causing the same problem.
Best of luck with it.
. .
 
As the master cylinder is new the modulator becomes quite suspect in this case cos the circuit splits within it to diagonal operation and it seems that the problem is only with the primary circuit(6a), it's possible that the inlet valves for that circuit to be sticky and when the pedal is released the caliper can't disengage well due to backpressure. I can's see a way to rule it out other than replacing the modulator . Eventually find a place where you can use HDC and let it work few times cos then the modulator is under shocks and maybe it gets unstuck. Was the system power bled with diagnostic tool ? when the master cylinder is changed this is compulsory for a proper modulator activity. The schemes should be relevant

Brake hydraulic circuit.jpg
ABS modulator.jpg
 
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sierrafery said:
As the master cylinder is new the modulator becomes quite suspect in this case cos the circuit splits within it to diagonal operation and it seems that the problem is only with the primary circuit(6a), it's possible that the inlet valves for that circuit to be sticky and when the pedal is released the caliper can't disengage well due to backpressure. I can's see a way to rule it out other than replacing the modulator . Eventually find a place where you can use HDC and let it work few times cos then the modulator is under shocks and maybe it gets unstuck. Was the system power bled with diagnostic tool ? when the master cylinder is changed this is compulsory for a proper modulator activity. The shemes should be relevant

View attachment 228795 View attachment 228796
Click to expand...
This is what I meant by "properly installed".
Even before the days of electronics interfering with braking, split circuit braking systems had valves that needed to be taken into consideration when bleeding brakes, changing fluid, etc, etc.
But actually I am sure this is going to turn out to be where the problem lies. either improper installation or a sticky or jammed or bust modulator.
Such a shame you spent so much money and time on all the other stuff.
 
While I'm in a moan mood, another one here where the op makes a query, receives some very detailed advice, and when I check his profile, doesn't to have come back after his initial post. Am I wrong here, can someone come online without logging in?
 
Kenbo said:
While I'm in a moan mood, another one here where the op makes a query, receives some very detailed advice, and when I check his profile, doesn't to have come back after his initial post. Am I wrong here, can someone come online without logging in?
Click to expand...
It would certainly be helpful to others if peeps come back on here & tell us if/how their faults are cured after posting.
 
Kenbo said:
While I'm in a moan mood, another one here where the op makes a query, receives some very detailed advice, and when I check his profile, doesn't to have come back after his initial post. Am I wrong here, can someone come online without logging in?
Click to expand...
You can come online and look, Except for AG, but you can't post unless you join.
AFAIK
 
meego said:
True. But it doesn't take long to have a look and see if anyone has come on with an answer, and perhaps say thanks. He is the one with the problem and is asking for help !! I've lost count of the times I have given advice to new members, only to never hear a peep from them.
Click to expand...
I know exactly what you mean :cool:
 
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