Why are my brakes so sh**e ?

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Martinez
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Why are my brakes so sh**e ?

Post by Martinez » 11 Sep 2019, 19:20

I’ve put new shoes in back, replaced compensator spring, stripped front calipers and checked everything, so why are my brakes still s**t ?
Brake pedal does go down if you hold your foot on it n start the engine, so vacuum seems to be working. When driving the pedal feels like the engine is stopped so to stop suddenly you need to virtually stand on it. What should I check next ?
I’ve consulted the Haynes Book of Lies, but it only mentions the servo and non return valve but doesn’t even say where they are !
HELP

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GiveMeABreak
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Re: Why are my brakes so s**t ?

Post by GiveMeABreak » 11 Sep 2019, 20:15

Have you changed the brake fluid and bled the system?

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xantia_v6
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Re: Why are my brakes so s**t ?

Post by xantia_v6 » 11 Sep 2019, 20:44

I would suggest that you might have the wrong grade of brake pad fitted, especially if someone has fitted "high performance" pads. High performance pads typically have a harder material which has less grip, but work better when the disks are near red-hot, which does not happen very often on a road car.

If you don't know what is fitted, I would suggest fitting a set of genuine pads, or some with oem-spec friction material.

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Doo
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Re: Why are my brakes so s**t ?

Post by Doo » 11 Sep 2019, 22:04

Martinez wrote:
11 Sep 2019, 19:20
I’ve put new shoes in back, replaced compensator spring, stripped front calipers and checked everything, so why are my brakes still s**t ?
Brake pedal does go down if you hold your foot on it n start the engine, so vacuum seems to be working. When driving the pedal feels like the engine is stopped so to stop suddenly you need to virtually stand on it. What should I check next ?
I’ve consulted the Haynes Book of Lies, but it only mentions the servo and non return valve but doesn’t even say where they are !
HELP
Are you saying the pedal goes hard soon as you press it in normal driving conditions?

I would suggest either a broken/leaking vacuum pipe or a worn vacuum pump.

I believe there may be a one way valve to the servo on these, but can't be certain as not enough time spent on the marque.

But I would start with the vacuum pipe in case it has split.

Martinez
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Re: Why are my brakes so s**t ?

Post by Martinez » 12 Sep 2019, 01:21

Yes the pedal feels like you’re pressing down on wood. There’s no feel to them and no progression in the pedal. The discs n pads are good on the front, bit of a glaze on the discs and the pads look like shiny graphite. There’s just no bite. I was going to check the system but can’t see where the servo and the valve are, no pictures in manual either.
While I’m here, there’s no caps on the driveshaft nuts either, is this the norm ?

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GiveMeABreak
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Re: Why are my brakes so s**t ?

Post by GiveMeABreak » 12 Sep 2019, 08:58

Is the brake compensator working correctly and you didn't specify if you bled or checked the condition of the brake fluid / filter.

To be honest we need a VIN so we know exactly what we are dealing with.

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Re: Why are my brakes so s**t ?

Post by Martinez » 12 Sep 2019, 09:26

viewtopic.php?t=62519
My vin was in a previous post as above. I was thinking of changing the fluid, but tbh I doubt it’s enough on its own to cause this problem. Motorway driving is scary. And it doesn’t seem possible to lock the brakes. It reminds me a little of when the rear calipers seized on my old Pug and I was standing on the brakes but it just wasn’t slowing down (the abs didn’t help either) good job there was a filter lane on the right for me to escape down.
Ive replaced the spring on the compensator after freeing it up, but I’ve also fitted spring assisters at the rear as it’s a campervan. Mot tester said all brakes passed ok, but they’ve never been good.
I’ve tried to get the compensator adjusted but nobody seems able to do it, so I set the spring as per instructions with spring assisters. I’ve suspected this is where my problem lies, but I’ve no real idea !

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GiveMeABreak
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Re: Why are my brakes so s**t ?

Post by GiveMeABreak » 12 Sep 2019, 09:35

Ok, I'll have a look now I have the VIN.

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Re: Why are my brakes so s**t ?

Post by GiveMeABreak » 12 Sep 2019, 09:47

Ok, so I'm not sure what facilities / equipment you have, but this is the method used to check the brake compensator:
Berlingo Brake 1.PNG
Brake Pressure Checking Equipment (4140-T)
Preparation
Vehicle in running order.
Brake system bled.
Place the vehicle on a four-column lift.
Connection of the checking equipment [1].

Connect:
The front pressure gauge to one of the front brakes
The rear pressure gauge to one of the rear brakes
Replace the bleed screws with the sensors.
Bleed the equipment (refer to the equipment instructions).
Chock the front wheels.
Place the rear wheels on scales.

Checking
The corrector is checked in relation to the weight on the axle (see the table below).

If the vehicle is heavier (see the table below): Raise the vehicle, by the body, using a hydraulic lift or a jack.
If the vehicle is lighter: Load the vehicle or pull on the body to obtain this load.
Press the brake pedal to obtain 100 bars on the front brakes.
The cut-off on the rear brake should take place at the pressure indicated in the table.
From the table, select the value which is closest to the actual weight on the vehicle axle checked and adapt this weight to the value in the table.
Pressure on the front brakes: 100 bars.
Vehicle typeWeight on
the rear axle (kg)
Pressure on the rear
brakes (in bars)
Utility vehicle : 475 kg40925
54026
67558
Utility vehicle : 600 kg41725
59627
77570
Utility vehicle : 800 kg41825
64432
87081
Adjustment
Berlingo Brake 2.PNG
Unscrew nut (1).
Load the suspension to the load which corresponds to 1 person(people) + 5 litres of fuel.
Establish a pressure of 20 bars minimum in the compensator.
Screw the adjusting nut ( 2) to the stop on the lever (3) while ensuring that the spring (4) is not under stress.
To do this, a shim will be used to set a clearance ( j) of 1 ± 0,5 mm between the nut (2) and the lever (3).
Support the adjusting nut ( 2) and lock it in position using the locknut (1).

Gibbo2286
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Re: Why are my brakes so s**t ?

Post by Gibbo2286 » 12 Sep 2019, 09:54

I think as mentioned earlier in the thread you have a failed servo, usually caused by damaged vacuum hose or pump but occasionally the diaphragm split in the servo itself, I very much doubt it is caused by your compensator or by the quality of the fluid.

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Doo
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Re: Why are my brakes so s**t ?

Post by Doo » 12 Sep 2019, 11:53

Any time I have happened upon a compensator problem it rears it's ugly head by being jammed fully open or fully closed.

It's only job is to divert fluid to the rear brakes.

The more weight you apply to the back of the vehicle, the more the suspension will sink, thus allowing the compensator valve to provide more braking force to the rear wheels.

If the compensator gets jammed with a lot of weight over the rear axle, then that weight is removed, sudden hard application of brakes will almost always cause the rear wheels to lock up.

If the compensator never has any real weight over the axle, it can fail to provide sufficient braking force to the rear axle which shows up as inefficient braking force on the brake rollers.

Either way, a bad compensator will not cause a rock hard pedal because the majority of the braking is done by the front brakes in most unladed vehicles cases.

Lack of servo assistance will cause a hard pedal and can be fatal.

I bought a BMW 535i a few years ago and was giving it large loud pedal and had to brake once, then again in rapid succession. The second time I applied the brake, the force required to push the pedal had me straining my leg as it was solid.

Turned out the brake pressure accumulator was on it's last legs. It was fine under gentle driving conditions, but when I really needed it, it surrendered :oops:

So, I would check the vacuum hose from the pump to the servo as they tend to get brittle or the rubber seal rots away and allows the vacuum to escape.

As the PPI Arnold tank says, Do it! Do it nowww :-D

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myglaren
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Re: Why are my brakes so s**t ?

Post by myglaren » 12 Sep 2019, 12:34

PP Arnold didn't say that at all :)

ekjdm14
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Re: Why are my brakes so s**t ?

Post by ekjdm14 » 12 Sep 2019, 16:26

Another vote for lack of servo assistance here, could well be a split pipe that's building vacuum at rest but separating and dumping vacuum when on the move. Definitely focus your attentions on the servo/pipework and vac pump IMO. Another rough test is to run the engine & then switch off and let it sit for a few minutes, then try the pedal & see how many applications you get (if any) before it goes solid again. Usually it should give you a few good servo'd applications if all is well but if there's a leak it'll be rock hard from the get go.

Not sure on your vehicle, but the master cylinder and servo should be easily visible under the bonnet, sometimes on the left side being French. If you've checked your brake fluid you've looked right at the servo as it'll be behind/under the fluid reservoir.

Gibbo2286
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Re: Why are my brakes so s**t ?

Post by Gibbo2286 » 12 Sep 2019, 17:12

I should have said earlier it's possible that the internal lining of the vacuum pipe has collapsed and is blocking the flow.

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Doo
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Re: Why are my brakes so s**t ?

Post by Doo » 12 Sep 2019, 19:14

myglaren wrote:
12 Sep 2019, 12:34
PP Arnold didn't say that at all :)
Well, not in the meaning of brakes, but the ones I saw, he was trundling along on his tank base and his head told me to "Do it! Do it naowwwwww!" :rofl2: