Brake faults! I must have ruined the brake system.

[Souster]

Hi all

Ever since I've owned the land rover, I've had a niggle that I can't seem to sort out. It's a 1995 defender 90 with an entire new brake system.

The problem I'm having is the brake pedal increases on corners, the sharper the corner, the more the pedal increases. For instance, if I reverse off my drive. The pedal travel increases, it's the same driving forward or reverse. The reason for posting and starting a new thread, is the problem is getting worse and more noticeable. Several mechanics I've seen have no clue!!

To try and solve the problem...

I've changed 3 stub axles, and all new timken bearings in 4 hubs. Adjusted as per rave, maybe slightly tighter to ensure zero play in the hub. They are very well packed with grease. This was due to thinking it was wheel bearing play because of turning sharply and off roading increasing the travel

New master, vacuum pump, pressure relief valve and servo 12 months ago (all oem)

Stainless pipes, new solid pipes, new Oem calipers, oem discs and pads.

More info:

If driving forward, and turn to full left hand lock the pedal travel will double. If I keep the steering wheel in the same place, the 2nd press of the pedal will be fine driving forward or reverse. As soon as I change to right hand lock, the exact same happens. Obviously this is just experimenting with the issue and giving you some information.

There is absolutely no play in the bearings from rocking the wheels jacked up with a crow bar, MOT tester agrees.

Now, something else I'd like to add... when asking around, people seemed to believe it may be a pedal box or servo issue. Fractures or something?? But I can't understand why. Although I'm finding, the vacuum pressure has disappeared within seconds of turning off the engine. Which seems wrong to me compared to other land Rovers I've driven.

On the road, driving normally, the 2nd press of the brake pedal, the vacuum pressure has been exhausted, which also seems wrong to me. The vacuum pump is new, so that's ruled out. The last pump was the same, hense me replacing it. On the MOT, with a entire new brake system, it's only performing at 62% which I believe is only just okay, which is very dissapointing after spending all this money.

Can anyone help me please? I'm sorry it's a long or repetitive thread. I can't afford to take it to a specialist, to charge me many hours of labour time and still not find the problem.

Thanks very much!

[Eightpot]

Wonder if the caliper pistons are retracting too far? Not sure why this would happen more on a corner though. Servo malfunction causing fluid to be drawn back? Some calipers do have a tendancy to withdraw pistons too far- are they standard calipers?

[Souster]

Wonder if the caliper pistons are retracting too far? Not sure why this would happen more on a corner though. Servo malfunction causing fluid to be drawn back? Some calipers do have a tendancy to withdraw pistons too far- are they standard calipers?

I was also wondering if it was a servo issue. The calipers are AP, I've changed the front for vented discs and calipers.

Thanks for the reply.

[MECCANO]

I recently tested my servo vacuum. The vacuum was still present 4 hours after I had last driven it.

[dailysleaze]

How are the flexi pipes? Are they stainless?

[Maverik]

I think you need to do some elimination...

What happens when you just have the engine running and you apply the brakes and you turn lock to lock? I'd maybe have a go at doing this with the front axle up on stands to take out the resistance of the ground....

Thought about putting a T off the vacuum line with a gauge on it track what the vacuum is doing?

[Souster]

I think you need to do some elimination... What happens when you just have the engine running and you apply the brakes and you turn lock to lock? I'd maybe have a go at doing this with the front axle up on stands to take out the resistance of the ground.... Thought about putting a T off the vacuum line with a gauge on it track what the vacuum is doing?

Ive tried the front axle on stands and the problem doesnt occur, neither does it stationary with the engine running. The reason behind changing all four wheel bearings and 3 stub axles was due to thinking it was wheel bearing play. However, none of the bearings had any issues, and neither did the stubs, they were very slightly worn, mainly on the seal lands but didnt need changing.

The only thing i can think of is over packing the wheel bearings, I only realised recently that i may put a little too much grease in there. But not enough to cause this kind of issue, especially doing 2000 miles, it would have settled and forced itself out.

Im not really sure if i have two seperate problems, or one main problem. The servo i removed off the vehicle was fine, slight rust around the mounting holes, but no cracks... Fitted a new one with no improvement. So then changed the vacuum pump and T piece, a reasonable improvement, but it still isnt holding the vacuum like it should be. So Is this a seperate issue to the steering affecting the brakes? or have i got a pedal box fault?

[Maverik]

As regards a pedal box "fault" I think that's clutching at straws as its only a pivot pin, and pretty much it, check the pedal for sides wards play, if there is non then I'd rule that one out.

Gaining travel still points to a bypassing mater cylinder on the front piston seal, why it only does it when cornering I do not know, but you could potentially check this my replacing the two input pipes on the master with bleed nipples and see if the will pump up and stay hard. and go for a drive and see what happens... being careful that you wont have any brake effort from the front of the vehicle....!!!!

Whenever I've had a master cylinder on it way out you get the characteristic of a dropping pedal with braking effort at the bottom of the stroke.

[Souster]

As regards a pedal box "fault" I think that's clutching at straws as its only a pivot pin, and pretty much it, check the pedal for sides wards play, if there is non then I'd rule that one out.

Gaining travel still points to a bypassing mater cylinder on the front piston seal, why it only does it when cornering I do not know, but you could potentially check this my replacing the two input pipes on the master with bleed nipples and see if the will pump up and stay hard. and go for a drive and see what happens... being careful that you wont have any brake effort from the front of the vehicle....!!!!

Whenever I've had a master cylinder on it way out you get the characteristic of a dropping pedal with braking effort at the bottom of the stroke.

Thankyou for you reply.

Ahh right i see, so basically the servo is the only thing that holds the vacuum? and the pedal box is basically just applying the lever action?

The brakes are fine in a straight line, although doesnt take much to exhaust the vacuum. If it was the master cylinder this would be the case it a straight line too surely?

What i have noticed from trial and error is... Driving in a straight line is fine, when i turn either way, the pedal increases slightly, the closer to full lock the longer the travel gets. If i remain turning the same lock forward or reverse (ie. in a circle), the 2nd press is fine no matter how long i drive in that circle the brakes are fine. As soon as i change lock to the opposite side, the travel increases again and the same happens over again. Something i forgot to add, when driving off road, the rougher the terrain, the more the brake pedal travel increases. Again pointing to wheel bearings, but there is absolutley sod all play.

Clutching at straws here, Could CV joint spacing have anything to do with it? inferior brake discs?

Failing sorting out the increased travel, do you guys think my servo is faulty and get it replaced?

[d-9]

Ahh right i see, so basically the servo is the only thing that holds the vacuum? and the pedal box is basically just applying the lever action?

There are three bits to the brake system, the hydraulic system with master cylinder, lines & hoses and calipers or wheel cylinders, the pedal box which applies leverage to the master cylinder, and the servo that provides pressure assistance and makes the brakes easier to apply.

As above, the pedal box is very simple, it is a pivot, pedal and some form of connection onto the master cylinder. Inspect it carefully with a decent lamp, look for any cracks, but fundamentally, its a pivot.

The servo is kinda irrelevant, you dont need it for the brakes to work. As a safety feature, the brakes must work without servo assistance, so I would pump off all the servo for testing, so you know you are testing the hydralics, not the servo. It sounds like your servo empties rather quickly, but maybe thats normal.

Get it up on a ramp, take the front wheels off and watch the front brakes while an assistant presses the pedal, checking the movement of the pistons in the calipers, then watch the pistons while the assistant turns onto full lock, checking to see if there is any movement in the pistons/calipers. Then watch while the assistant presses the pedal. If everything is behaving normally, the issue is upstream of the calipers. Watch the flexi-hoses carefully as the assistant turns from lock to lock, they should move freely, not be stretched or come close to the wheels.

As above, I would suspect the master cylinder. Once the travel issues are fixed, look at the servo capacity issues.

Ive never heard of a system gaining travel when turned, its a very odd issue.

[Eightpot]

Increased travel = either air in system, faulty seals or pads have to move longer to hit disc.

Starting from the top, is pedal attached correctly to master cylinder push rod. Is master cylinder good (don't trust it just because it's new ) Are discs good - cheap discs can be out of true and cause pads to be pushed back. Faulty bias valve. Are flexy hoses good. Are they long enough? (raised suspension stretching them on full lock) . Your new calipers may be retracting brake pads, common with some td5 models, worth measuring gap with feeler gauge.

Its going to be something simple and silly, enough worn out old landys knocking about with worn bearings and hubs but sharp brakes.

[Souster]

There are three bits to the brake system, the hydraulic system with master cylinder, lines & hoses and calipers or wheel cylinders, the pedal box which applies leverage to the master cylinder, and the servo that provides pressure assistance and makes the brakes easier to apply.

As above, the pedal box is very simple, it is a pivot, pedal and some form of connection onto the master cylinder. Inspect it carefully with a decent lamp, look for any cracks, but fundamentally, its a pivot.

The servo is kinda irrelevant, you dont need it for the brakes to work. As a safety feature, the brakes must work without servo assistance, so I would pump off all the servo for testing, so you know you are testing the hydralics, not the servo. It sounds like your servo empties rather quickly, but maybe thats normal.

Get it up on a ramp, take the front wheels off and watch the front brakes while an assistant presses the pedal, checking the movement of the pistons in the calipers, then watch the pistons while the assistant turns onto full lock, checking to see if there is any movement in the pistons/calipers. Then watch while the assistant presses the pedal. If everything is behaving normally, the issue is upstream of the calipers. Watch the flexi-hoses carefully as the assistant turns from lock to lock, they should move freely, not be stretched or come close to the wheels.

As above, I would suspect the master cylinder. Once the travel issues are fixed, look at the servo capacity issues.

Ive never heard of a system gaining travel when turned, its a very odd issue.

Thanks for the reply. I did very similar to what you suggest. Pumped the brakes as much as i could, reversed off the drive and turned the vehicle as much as i could without pressing the brakes. I then took each wheel off, and checked each caliper to see which pads and pistons were pushed back. i couldnt see a thing? Nothing strange or any different to another.

Do you suspect faulty master cylinder then? Even when the pedal only increases when cornering?

Increased travel = either air in system, faulty seals or pads have to move longer to hit disc.

Starting from the top, is pedal attached correctly to master cylinder push rod. Is master cylinder good (don't trust it just because it's new ) Are discs good - cheap discs can be out of true and cause pads to be pushed back. Faulty bias valve. Are flexy hoses good. Are they long enough? (raised suspension stretching them on full lock) . Your new calipers may be retracting brake pads, common with some td5 models, worth measuring gap with feeler gauge.

Its going to be something simple and silly, enough worn out old landys knocking about with worn bearings and hubs but sharp brakes.

thanks eightpot. Its 110% not air, im very confident with that. Pedal is attatched correctly from servo to MC, ive checked. If it was the discs, wouldnt that occur when driving in straight line too? Im not 100% they are genuine TRW discs, they were from ACE parts online.

Bias valve new, stainless braided hoses that are not fouling and are the perfect length.

Do you also beleive its the master cylinder? even though it only occurs when turning? I have had issues with the rear brakes not working very well. they certainly take a while to clear the rust of the discs. On the MOT the brake system only reached 62% which i think is poor considering everything is new.

Thanks all

[miketomcat]

I have a slightly random pedal on 45 it's due to air in the system but I can't get it out (believe me I've tried) so I just live with it. To be honest it's not enough to cause concern but enough to "wake" me up from time to time.

Mike

[GW8IZR]

it doesn't do it stationary and it doesn't do it when on axle stands. It does it on the road and its worse when bouncing around off road.

So its worse when brake fluid is sloshing about in the reservoir? is there a clue in that?

When you replaced the master cyl was there anything odd about the resevoir ports?

[Souster]

it doesn't do it stationary and it doesn't do it when on axle stands. It does it on the road and its worse when bouncing around off road.

So its worse when brake fluid is sloshing about in the reservoir? is there a clue in that?

When you replaced the master cyl was there anything odd about the resevoir ports?

It's mainly on more articulating off road areas to tell the truth.

Again pointing to bearings. But I have access to two other old land rovers, and the bearing play on them compared to mine is very noticeable.

Thanks for the replies chaps

[Eightpot]

I've found a large percentage of components to be faulty from new, not just cheapo brands. I run a small repair workshop and come across it often - just put new TRW clutch master and slave on a defender and they don't hold pressure. Declining standards or counterfeit parts dunno but I don't eliminate parts from a problem just because they're new.

Just thinking about a job I had a problem with a while ago, some symptoms were similar- the seal/gasket between master cylinder and servo was not good and would let pressure escape. If seal was tight the servo would work well and give great pedal feel. If air escaped pedal had to be pressed harder and further to get good bite. Put a new gasket and some sealant on and brakes were tip-top again.

[Retroanaconda]

Changes while steering or articulating point to the flexible hoses I would have thought?

I know they're new but as above doesn't mean they are good!

[Souster]

Thanks guys. I'm certain it's not the master cylinder to servo seal, but I will double check the flexis.

I've just been looking through the paper work I have with the vehicle. And back in 2009, the servo and master cylinder was replaced. Notes in the invoice state "due to poor brake efficiency".

Mind you, if the calipers were anything like the state I picked it up in 2013/14 then I'm not surprised there was poor brake efficiency.

I'll double check the flexis again, and move them about with an assistant to see if that highlights anything.

Failing that, is it worth trying to see if I can get a new master cylinder under the guarantee?

Other questions I want to ask:

-could the discs be inferior on the front?

-Why does the pedal only sink on start up sometimes, linked?

-I've been asking around, and apparently fractures in the pedal box aren't Un heard of, they can cause adittional movement in the pedal box when the steering is turned apparently. But that wouldn't explain the poor vacuum? Has anyone heard of this and where do I start looking?

Should the brake fluid to the rear brakes when bleeding be half or less than the fronts? As they were the other day when I bled.

[pete3000]

Think i've mentioned before, the stainless braided hoses are bling but a source of problems on my 110. I trashed the rear one by clamping it. (You can't as they don't like it).

The fronts could never get a good pedal. swapped to standard rubber all round and they are much better. (can clamp them and the inside pipe bore is bigger?).

I bought the stainless +4" hose set as I bought the procomp dampers es9000 with the britpart hd+2" 420lb springs made one necessary at the back.

before you lash out on a new servo, try a new one way valve push in valve in the servo to see if it is leaking.

I too had a couple of duff master cylinders, latest one was ebay exmod surplus in a trw box. This one i have had no issues with.

[Souster]

Morning guys, and thanks for the reply Pete.

Ive replaced that one way valve on the servo, made no difference.

Right i did some testing this morning with the vacuum pump disconnected as follows:

Brake pedal pumped to get the pedal as hard as possible, i then wiggled the two front flexi pipes in all directions, to act like turning or off road. It made no difference to the brake pedal at all.

With the brake pedal still hard, i reversed off the drive on full right hand lock, the pedal then doubled in travel! While i had stopped to engage 1st gear to go forwards, i pumped the pedal back up hard again. Once i started going forward a few metres, the pedal travel doubled once again.

Exactly the same thing aplied to left hand lock. I must admit though, its much harder to detect the pedal differences without the vacuum pump connected. Infact if i was actually searching for a fault, i probably wouldnt be able to tell.

When the brake pedal is actually in the lower position from turning sharply etc, it take a good many pumps of the pedal to get it back to its best position. Which i thought was strange, if it was knocking the brake pistons back slightly, one or two presses would bring them back into the disc/pad wouldnt it? again im clutching at straws really. Just trying to find the answer.

Thankyou all

[cackshifter]

The loss of vacuum might be explained by the seal between the servo and the master cylinder not working - there is supposed to be an O ring. Are you sure the pipe between pump and servo is OK too? Re the pedal travel,you can usually get a harder pedal if you pump it a bit on any system, but if you are getting double the travel it can only be the pads getting kicked back, air in the system or a duff master cylinder, assuming no leaks. When the pedal travel increases, is it spongy or hard but just much further down? Does it do it if you drive straight?

[Souster]

The loss of vacuum might be explained by the seal between the servo and the master cylinder not working - there is supposed to be an O ring. Are you sure the pipe between pump and servo is OK too? Re the pedal travel,you can usually get a harder pedal if you pump it a bit on any system, but if you are getting double the travel it can only be the pads getting kicked back, air in the system or a duff master cylinder, assuming no leaks. When the pedal travel increases, is it spongy or hard but just much further down? Does it do it if you drive straight?

The seal between the servo and master cylinder was changed with the new servo. I also used silicon where that O ring was on the last servo to rule it out.

I'm not 100% sure that pipe feeding the servo from the vacuum pump is okay, although I have fetched it off and inspected it and couldn't see any issues. As soon as I turn off the engine, the vacuum is lost so it's a fairly big leak (same with both vacuum pumps).

As for air in the system, I'm certain there is none. It's been bled too many times, even did it last week and there wasn't any. The pedal feels too good in a straight line for it to be air as well, even though the stopping of the vehicle isn't great.

I would say when the travel increases, it's very very slightly more spongy (perhaps clutching at straws again). But mainly just increase in pedal travel.

Thanks cackshifter

[Guest]

Silly question but when you reverse off the drive on left lock does this happen?

Does the body roll when you are turning I.e adverse camber?

The reason I ask is that I have seen something very similar before, chap had the brake lines renewed with new flexible hoses also, the hoses seemed fine on full lock but what he didn't take into account was the body roll that pushed the hoses over length and lead to poor breaking but no fluid loss.

It turned out that when the new brake pipes were fitted they were just a little short on one side hence the hose just being that few mm too short at full travel/lock.

From the sounds of it your servo could be an unrelated issue just confusing matters and making the travel worse on loss of vacuum and it could I fact be your vacuum pump that is not up to the job. Have you tested it? Electric pumps are a couple of quid from the breakers you could hook one up and see if that improves the vacuumed situation.

Finally although you say that you have bled the system have you changed the fluid recently with all the changes and new parts it is possible that it could have become slightly contaminated and when put under pressure as above could be compounding the issue.

Where are you located?

Jason

[Souster]

Silly question but when you reverse off the drive on left lock does this happen?

Does the body roll when you are turning I.e adverse camber?

The reason I ask is that I have seen something very similar before, chap had the brake lines renewed with new flexible hoses also, the hoses seemed fine on full lock but what he didn't take into account was the body roll that pushed the hoses over length and lead to poor breaking but no fluid loss.

It turned out that when the new brake pipes were fitted they were just a little short on one side hence the hose just being that few mm too short at full travel/lock.

From the sounds of it your servo could be an unrelated issue just confusing matters and making the travel worse on loss of vacuum and it could I fact be your vacuum pump that is not up to the job. Have you tested it? Electric pumps are a couple of quid from the breakers you could hook one up and see if that improves the vacuumed situation.

Finally although you say that you have bled the system have you changed the fluid recently with all the changes and new parts it is possible that it could have become slightly contaminated and when put under pressure as above could be compounding the issue.

Where are you located?

Jason

Thanks for the reply Jason.

Unfortunately, the suspension was plus 2" when I bought it. Although it does sit nice and just slightly higher than standard. I fitted terrafirma plus 2" braided flexis to the front and they don't look too long or short in all honesty.

The same does happen when I reverse off the drive at left hand lock. I don't mind if the pedal just drops when reversing off the drive, but the fact you can feel it on the road lately concerns me and doesn't give me much confidence. It seems even worse off road.

As for the brake fluid, it's about as new and as fresh as it gets. Perfectly clean and the oldest fluid in the system will only be a couple of months old.

[western]

there isn't a seal or gasket between the master cylinder & servo on 90/110 braking system, nothing shown on the

pre 300tdi servo http://lrcat.com/#31/4/52910 [definitely no seal on my servo/MC joint]

or the

300tdi onwards servo http://lrcat.com/#31/4/52909

try a vacuum leak check on the servo body joint, that maybe the cause of loss of vacuum = long pedal travel