Urgent Brake Help!!!!!!!!!!!!!!!!!!!

[NiftyNev]

.....its not unusual for a diesel engined vehicle pedal to continue to creep almost to the floor with engine running!

If it does then you have an internal leak in master cylinder. The pedal height should not change. The only way it can is if the fluid has somewhere to escape. If this is not through an external master cylinder or slave cylinder leak or any of the other components such as brake lines, wheel cylinders, disc calipers etc then it will be the master cylinder internal seals.

Nev

Edit: Ignore the slave cylinder reference. I was thinking of the clutch.

[meooo]

If it does then you have an internal leak in master cylinder. The pedal height should not change. The only way it can is if the fluid has somewhere to escape. If this is not through an external master cylinder or slave cylinder leak or any of the other components such as brake lines, wheel cylinders, disc calipers etc then it will be the master cylinder internal seals.

Nev

no it does not mean any such thing.
vehicles were being failed on mot for this and a special notice was released.
If the pedal doesn't creep with engine off but does with servo assist, it cannot be a leak! It would creep without the servo if it did have a leak! Travel is increased with servo action, the diesel uses a vacuum pump and will continue to pull the pedal down if you maintain pressure on it.
Even new vehicles will do this.....it doesn't mean there is a leak anywhere. test for leaks WITHOUT the engine running and after evacuating the servo!

[NiftyNev]

no it does not mean any such thing.
vehicles were being failed on mot for this and a special notice was released.
If the pedal doesn't creep with engine off but does with servo assist, it cannot be a leak! It would creep without the servo if it did have a leak! Travel is increased with servo action, the diesel uses a vacuum pump and will continue to pull the pedal down if you maintain pressure on it.
Even new vehicles will do this.....it doesn't mean there is a leak anywhere. test for leaks WITHOUT the engine running and after evacuating the servo!

Forget the servo, all it does is save on the leg muscles. It has nothing to do with the hydraulics except to assist in it's operation. Perhaps you would like to explain where the fluid goes then. It's a hydraulic system and when the calipers, wheel cylinders and brake lines etc are full and pads and shoes have bottomed out then that should be the limit of travel providing hoses do not start to swell. Fluids do not compress so why would the pedal continue to creep? I'll tell you why. It's because of a leak somewhere, be it external, or internal.

Nev

[meooo]

OK
Try sitting in vehicle, no engine running and pump brake pedal until hard.
Maintain pressure on pedal and start engine....if the servo is working pedal will drop.....this is the servo action and not a fluid loss and is the reason for testing for leaks without engine running!

There is no direct link between pedal and m/cylinder (unless you use an indirect servo) pedal operates servo, servo operates m/cyl. The vacuum operates servo, servo pulls down pedal if its working, its NOT an indication of fluid loss. TEST FOR LEAKS WITHOUT ENGINE RUNNING!


IF m/cylinder is leaking there will often be fluid inside the servo, not in the car, with the m/cylinder removed check inside servo for fluid......this fluid can be sucked through the vac pump and not be readily found

[NiftyNev]

I am not talking about an external leak where there is actual fluid loss. I am refering to the master cylinder internal leak where fluid passes by the seals as the pedal is being depressed and then returns the same way when the pedal is released. This is what can cause the pedal to continue to creep. I can hold my foot on the brake all day and the pedal will remain in the same position.

Nev

[darkdezigns]

OK
Try sitting in vehicle, no engine running and pump brake pedal until hard.
Maintain pressure on pedal and start engine....if the servo is working pedal will drop.....this is the servo action and not a fluid loss and is the reason for testing for leaks without engine running!

There is no direct link between pedal and m/cylinder (unless you use an indirect servo) pedal operates servo, servo operates m/cyl. The vacuum operates servo, servo pulls down pedal if its working, its NOT an indication of fluid loss. TEST FOR LEAKS WITHOUT ENGINE RUNNING!


IF m/cylinder is leaking there will often be fluid inside the servo, not in the car, with the m/cylinder removed check inside servo for fluid......this fluid can be sucked through the vac pump and not be readily found

sorry matey but nifty is right,the reason your pedal drops when u start the engine with foot on pedal is cause your then activating the servo

[tintin]

All Questions answered........
1 The pedal is rock hard and does not depress when engine is off.
2 With engine running, pedal feels slightly spongey, and will 'creep' down to the floor
Surely Meoo, if this were meant to happen then i would not be able to hold the vehicle on a hill for more than a few seconds before the pedal hits the deck and i lose my braking! ?
( hope that makes sense)

By clamping off the rubber hoses, we have physically eliminated the front wheel calipers, and the rear wheel cylinders from the equasion. So with no visible leaks and no fluid loss from the reservoir, the master cylinder has to be letting by internally!
( at least i hope so, cos Milners have sent me a replacement!)
(can't fault thier service)
Just got to find time to replace it now, probably have to wait til next saturday
(that'll be two weeks 'er indoors' has been car-less)( boy is she happy!!)

Alan

[darkdezigns]

sure it will be fine

[meooo]

All Questions answered........
1 The pedal is rock hard and does not depress when engine is off.
2 With engine running, pedal feels slightly spongey, and will 'creep' down to the floor
Surely Meoo, if this were meant to happen then i would not be able to hold the vehicle on a hill for more than a few seconds before the pedal hits the deck and i lose my braking! ?
( hope that makes sense)

By clamping off the rubber hoses, we have physically eliminated the front wheel calipers, and the rear wheel cylinders from the equasion. So with no visible leaks and no fluid loss from the reservoir, the master cylinder has to be letting by internally!
( at least i hope so, cos Milners have sent me a replacement!)
(can't fault thier service)
Just got to find time to replace it now, probably have to wait til next saturday
(that'll be two weeks 'er indoors' has been car-less)( boy is she happy!!)

Alan

Thank goodness for that, someone trying my suggestion and proving the point I was making

You dont have a leak then....I suggest you give it a couple of hundred miles for pads to bed in, you wont have a problem.

During "normal" driving, you wont notice the creep effect and pedal wont reach the floor, it will stop 1-2 inches off.
Sometimes you will need a car to stand for 24 hours before the pedal comes back after fittiing pads (Astra diesel/Corsa come to mind) but you could avoid that by opening the bleed nipples before pushing back the caliper pistons.

Do you have ABS? as you could be "exciting" the valve block into operation by repeatedly pumping the pedal....this would illuminate the dash warning light.

[NiftyNev]

Thank goodness for that, someone trying my suggestion and proving the point I was making

You dont have a leak then....I suggest you give it a couple of hundred miles for pads to bed in, you wont have a problem.

During "normal" driving, you wont notice the creep effect and pedal wont reach the floor, it will stop 1-2 inches off.
Sometimes you will need a car to stand for 24 hours before the pedal comes back after fittiing pads (Astra diesel/Corsa come to mind) but you could avoid that by opening the bleed nipples before pushing back the caliper pistons.

Do you have ABS? as you could be "exciting" the valve block into operation by repeatedly pumping the pedal....this would illuminate the dash warning light.

Nev

[meooo]

Nev

Of course, none of this is relevant to any vehicle in Australia, which apparantly have completely different braking systems to all other countries.

Vehicles imported to UK/Europe obviousley have braking systems changed over to "normal" @ point of import.

[Apache]

You cant 'excite' the ABS system into operation by pumping the pedal.

And only third gens on have ABS - except in Australia...

[Sancho]

All this talk of pumping's got me excited....

Anyway, Nev is right. If the hoses have been clamped off, eliminating the possibility that it could be the set up of the brakes (i.e. pads bedding in), you are pretty much only left with a pedal, a servo and a master cylinder. The pedal works (obviously), the servo works (it goes hard when you pump the brake with the engine off and drops when you switch on) so the only thing left is the master cylinder.

It sounds like it is not leaking externally (no reduction in fluid level in the braking system) and the system has been bled (I would check some more), so it must be a problem with the internal seals, surely????

[meooo]

All Questions answered........
1 The pedal is rock hard and does not depress when engine is off.
2 With engine running, pedal feels slightly spongey, and will 'creep' down to the floor


Alan

A leak will occur with or without engine running......

"1 Pedal is ROCK HARD with engine off"



unless of course you're an Australian

[NiftyNev]

Of course, none of this is relevant to any vehicle in Australia, which apparantly have completely different braking systems to all other countries.

Nothing is changed on the braking system when the vehicles are imported and I doubt it happens in the UK or anywhere else either. Only some third gen Surfs have ABS even in Australia.

Nev