Bleeding Brake Problem

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Re: Bleeding Brake Problem

Post by qwakers »

if you can get the car to me i will sort it for you. i will rob parts off my car until it works. i like a challenge and this promises to be a good one :D
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Re: Bleeding Brake Problem

Post by mrspiller »

qwakers wrote:if you can get the car to me i will sort it for you. i will rob parts off my car until it works. i like a challenge and this promises to be a good one :D
Good on you ImageImage
Well done for offering


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Re: Bleeding Brake Problem

Post by ChrisHolmes »

I cannot recall if you have had the master cylinder in pieces and fitted new seals? If so then dare I suggest you strip it down and make sure the seals are fitted correctly and not damaged. Once that is eliminated then start the bleeding process all over again.
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Re: Bleeding Brake Problem

Post by boosted »

This is a weird fault, good on you Qwakers!

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Re: Bleeding Brake Problem

Post by ChrisHolmes »

Surely we have member nearer to Milton Keynes than Cornwall who can work on the car.
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Re: Bleeding Brake Problem

Post by warpc0il »

The only time I've come across a brake that would lock on, where it wasn't the caliper, was on an Astra that had had some previous front impact damage.

It was obvious that the track rod and a coupes of associated suspension parts had been replaced but the flexible brake hose hadn't.

Replacing that hose fixed the problem and when we cut the old hose apart we discovered that the inner lining was torn and created a flap, which was acting as a non-return valve.

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Re: Bleeding Brake Problem

Post by Liam22 »

I think we need a definition/description of "locking". I assumed locking-up...

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Re: Bleeding Brake Problem

Post by RobinPZ72 »

This sounds like the ram in the master cylinder defective! Now bare with me and to be honest I've never taken car one to bits, but if the downwards stroke seal is worn or has a defect it would have this issue!

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Re: Bleeding Brake Problem

Post by mrspiller »

I’m not quite clued up on the whole thread just the start , have you changed back to original bits except the bleed nipples and tried it ?
And you could get the new pressure tested In the meantime ?
What brand are currently used ?


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Re: Bleeding Brake Problem

Post by geofftl1000r »

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Re: Bleeding Brake Problem

Post by Paulie »

Something that liam22 said in another thread, I've never done it engine running but certainly something I will consider in future.....
Quote
"As I do this before every race meeting I have a couple tips:

1. Bleed with the engine running so that the ABS lines are open. Essential if you have any air in the system. Even if you don't, the flow rate is much increased and makes the whole job quicker.

2. Pump the brake pedal so that it is firm before and after bleeding each caliper. If you introduced any air then you immediately know which caliper to go back to......."


Also ....
Not sure if it is possible, but is it possible to blank off 3 of the calipers at the master and just try bleeding one (closest) caliper straight to the master?
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Re: Bleeding Brake Problem

Post by Ashman »

I've changed the master cylinder twice, i have three now including the original.

I've had the abs module tested and a new mechanical half fitted, the electrical side was fine.

The calipers were all stripped, cleaned, pins greased and fitted along with new pads, discs, new pins, bleed screws (fitted with a little plumbers tape) and braided brake lines.

The car has been bled by myself, my old man, a mechanic and at the Mazda dealership where i bought the car. It's had well over 5 litres of fluid through it.

The car was driven by the Mazda mechanic and myself (last night) and on initial braking the pedal goes to the floor but if you pump the pedal it goes hard but then quickly loses that pressure.

I've checked under the car myself as well as Mazda and we can't find any leaks anywhere.

When bleeding the brakes the fluid shoots out nice and quick so there's definitely good pressure, there's also no air bubbles coming out.

I've tried blocking off the master cylinders i have with the blanking screws that the Mazda mechanic gave me and put my foot on the brake and each time the pedal only goes down a little way and stops. I assume that means the MC's are ok?

I've also tried running the wheels while on stands and stamping on the brakes but that did nothing.

This is what i've tried so far and to be honest i am all out of ideas. Especially if both Mazda and a rotary specialist are both stumped.
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Re: Bleeding Brake Problem

Post by Ashman »

I've been scouring the interwebs for a solution and i just read that the rear center brake light can have an effect on the ABS. The brake light was disconnected when i bought the car, actually the wiring was just cut, do you think this could cause a problem and what could could it knock out? I have already re-soldered the wires together and it lights up ok but that was before i tried bleeding the brakes.
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Re: Bleeding Brake Problem

Post by Liam22 »

My car runs without centre brake light and I have no issues. ABS works as before.

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Re: Bleeding Brake Problem

Post by warpc0il »

A short in the rear centre brake light, or an led replacement without a suitable resistor, can cause the abs to fail its self-test, which will result in the warning light remaining lit and the system being deactivated.

However, a deactivated abs just means that it can't release pressure when it detects a wheel lock.
That's should have no impact on filling or bleeding the system.

The reason for bleeding the system with the engine running is for vacuum power assistance, not abs.
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Re: Bleeding Brake Problem

Post by qwakers »

wedge the brake pedal down overninght and see of you get a pedal in the morning. youre looking for a fluid level drop. if you get any drop in the level you either have got rid of a ir lock or you have a leak somewhere.


you have two reasons as far as i can see for your current problem.

1) you have a leak. its possible one of the brake lines is porous or a seal in a replaced component is not doing its job. having left it wedged overnight you'll have a puddle to identify the leak

or

2) you have a stubborn airlock

if so, your problem will be suddenly gone...
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Re: Bleeding Brake Problem

Post by mrspiller »

qwakers wrote:wedge the brake pedal down overninght and see of you get a pedal in the morning. youre looking for a fluid level drop. if you get any drop in the level you either have got rid of a ir lock or you have a leak somewhere.


you have two reasons as far as i can see for your current problem.

1) you have a leak. its possible one of the brake lines is porous or a seal in a replaced component is not doing its job. having left it wedged overnight you'll have a puddle to identify the leak

or

2) you have a stubborn airlock

if so, your problem will be suddenly gone...
It has to be a fault with the changed components surely ?
I’ve think I’ve got a spare set of calipers and some ( not all ) brake pipes your welcome to try if you cover the postage


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Re: Bleeding Brake Problem

Post by qwakers »

ive had rediculously stubborn air locks before. completely impossible to bleed, until i did what i mentioned.
Last edited by qwakers on Sun Oct 21, 2018 9:37 pm, edited 1 time in total.
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Re: Bleeding Brake Problem

Post by Liam22 »

qwakers wrote:ive had rediculously stubborn air locks before. completely imossibke to bleed, until i did what i mentioned.
Me too. The overnight wedge is a goodun. When this also failed, bleeding with engine running was the answer.

So I disagree with warpcoil about it only being about servo.

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Re: Bleeding Brake Problem

Post by ChrisHolmes »

Thinking outside the box and I have never done this but let's think about doing the bleeding backwards by disconnecting the brake pipes at the highest point and then at the lowest point and fitting a flexible pipe that has its upper end higher than the upper end of the brake pipe in a container that can gravity feed brake fluid through the pipe. Once the fluid appears at the top end refit that union and then disconnect the pipe from the lower end and refit the lower union. Repeat on all pipes.
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Re: Bleeding Brake Problem

Post by geofftl1000r »

It doesn't take any pressure to get a good stream of fluid shooting out of an open nipple. You could get the same by putting some (none poisonous) fluid in a plastic tube and blowing into the tube, so that's like 1 psi. Probably not enough to bring a car to a halt.

We all know that fluid cannot be compressed. So it must be going somewhere. If it's not leaking (the reservoir would be going down) then there must be somewhere for the fluid to push into under pressure (ABS module?) or the master cylinder simply isn't building or holding pressure.
I have found in the past when bleeding callipers after a rebuild it's best to make sure the pistons are all fully pushed in to displace as much air as possible before trying to fill with fluid by bleeding.

Hope you get this sorted soon. I should be free next weekend if you want an extra pair of hands/fresh pair of eyes?
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ChrisHolmes (Sun Oct 21, 2018 11:41 pm)
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Re: Bleeding Brake Problem

Post by Ashman »

I wedged the brake pedal twice overnight and nothing, no level drop either. I'm going to get the hard lines renewed, there's probably going to be a pin hole leak somewhere but i cannot find any fluid on the floor. If i replace them then everything has been swapped out so if it doesn't work after that then i give up. Though i don't think i'll get it done this side of Christmas now. If anyone wants to come and take a look then you're more than welcome and greatly appreciated :thumleft:
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Re: Bleeding Brake Problem

Post by ChrisHolmes »

if you had a fluid leak then you would have seen the evidence by now so I doubt replacing the pipes is going to change anything.
Do you get any sort of resistance at all when you pump the pedal?
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Re: Bleeding Brake Problem

Post by RobinPZ72 »

I had on my Grand Voyager the tiniest pin hole, which sprayed just a fine mist that you couldn't see unless you actually seen it spraying! It would brake but fade over a week and drove me crazy until I was bleeding it yet again and felt this spray on my leg. It came from a joint that a garage linked a new brake line and the mushroom was sh*t!

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Re: Bleeding Brake Problem

Post by geofftl1000r »

So you are pretty lucky with brake faults then? :crybaby:
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