Help! No Brake Pressure

[Galaxy_Quest]

Hi all,

 

Gal failed MOT on brakes and some other bits and bobs. We have a 2.3 Zetec early Mk2 on W plate (2000).

 

Brake Pads: I changed the brake pads on the offside then realised I had to also bleed the system. Silly Ford TIS manual says TOTALLY take apart caliper and brake lines. Later realised didnt need to !!!! Anyway, one by one bled the brake systems using the little nipple on the caliper... kept the fluid topped up under the hood and pumped pedals until no more air in the system and all bubbles (even tiny ones) gone. Bleed valve closed and cap replaced.

 

As work done roadside in front of house, did offside front and back, then moved car so i do the drivers side. Obviousl no proper brake pressure then.

 

Did brake pads for driver side front and back, bleeding system while wheel was off (as above).

 

Took car for spin round block but brake pedal depresses fully and hardly any pressure "pushing back" on pedal. Is there something I have missed ?

 

HELP please folks! MOT retest due tomorrow am. :unsure:

[chromedome]

When you pushed the calipers back did you release the bleed nipple to drain the excess fluid? If you just push the calipers back in forcing the fluid through the system, you may have inverted the seals in the master cylinder or even worse screwed the ABS.

[RADIOTWO]

Hi all,

 

Gal failed MOT on brakes and some other bits and bobs. We have a 2.3 Zetec early Mk2 on W plate (2000).

 

Brake Pads: I changed the brake pads on the offside then realised I had to also bleed the system. Silly Ford TIS manual says TOTALLY take apart caliper and brake lines. Later realised didnt need to !!!! Anyway, one by one bled the brake systems using the little nipple on the caliper... kept the fluid topped up under the hood and pumped pedals until no more air in the system and all bubbles (even tiny ones) gone. Bleed valve closed and cap replaced.

 

As work done roadside in front of house, did offside front and back, then moved car so i do the drivers side. Obviousl no proper brake pressure then.

 

Did brake pads for driver side front and back, bleeding system while wheel was off (as above).

 

Took car for spin round block but brake pedal depresses fully and hardly any pressure "pushing back" on pedal. Is there something I have missed ?

 

HELP please folks! MOT retest due tomorrow am. :unsure:

 

Hello Avenger

 

I don't know how you performed the bleeding bit, but why did you undo the hydraulics when just doing a pad change?

 

But this is the way to bleed brakes:

Pump and Hold Method: One person pumps the brake pedal to compress the air, then holds pressure on it. The other person opens the bleeder valve to let out fluid and air, then closes the valve after the pedal has landed (to prevent air being sucked back in through the valve on the upstroke). The process is repeated, sometimes many times, for each wheel. Usually a length of clear tubing is connected to the bleeder valve and run to a container during the process, both to collect the toxic brake fluid and to better view the fluid and bubbles. The master cylinder reservoir must be replenished frequently, for if it goes dry the entire process must be redone. The cover must be left loose so that the fluid may be drawn, but should be in place so that fluid does not squirt out on the return stroke. It may be a good idea to not let the pedal bottom out during this procedure, as the master cylinder seals may be damaged by encountering accumulated sediment and / or corrosion.

 

Hope this helps?

 

Radiotwo.

Edited March 13, 2007 by RADIOTWO

[RADIOTWO]

When you pushed the calipers back did you release the bleed nipple to drain the excess fluid? If you just push the calipers back in forcing the fluid through the system, you may have inverted the seals in the master cylinder or even worse screwed the ABS.

Hi chromedome

 

You don't release the bleed nipples to replace the pads, as you might get air in the system, then you get

the problems "Avenger" has got

 

so unless you are doing a fluid change DONT let air in

 

Radiotwo

[Guest wolfie]

You don't release the bleed nipples to replace the pads, as you might get air in the system, then you get

the problems "Avenger" has got

 

so unless you are doing a fluid change DONT let air in

 

Radiotwo

 

so how exactly do you push the pistons back without clamping off the flexi lines and releasing the excess fluid via the bleed nipples? do you advise back flushing the fluid through the ABS valve block to the reservoir and allow it to over flow?

 

to quote Haynes, not the most technicall of manuals but it does the job

THE ABS UNIT CONTAINS HYDRAULIC COMPONENTS THAT ARE VERY SENSITIVE TO IMPURITIES IN THE BRAKE FLUID, EVEN THE SMALLEST PARTICLES CAN CAUSE THE SYSTEM TO FAIL THROUGH BLOCKAGE. THE PAD RETRACTION METHOD DESCRIBED HERE PREVENTS DEBRI IN THE BRAKE FLUID EXPELLED FROM THE CALIPER FROM BEING PASSED BACK INTO THE ABS HYDRAULIC UNIT

 

the method mentioned is to clamp off the lines and undo the bleed nipples to allow the fluid to exit the caliper as you retract the piston

[Galaxy_Quest]

Hi everybody,

 

According to the Ford TIS manual which I have on disc and instaled on my pc :unsure: it recommends disconnecting the front caliper from the brake hose after clamping it shut. I did do this on the first offside caliper but then realised this was unnecessary.

 

I did let the brake fluid out by loosening the valve and taking the plug off the nipple, otherwise you cant generate the pressure (without a piston pushing screw tool) to push the piston back out in the caliper housing before refitting it oover the new brake pads.

 

I have read somewhere about brake fluid / hydraulic "circuits". Are the fronts one one circuit and the rears on another? I did offside first, swapped the car round then did the driverside after that. Maybe this has caused a problem... who knows...anyone???

 

We were careful to use clean new brake fluid and not contaminate the system. We used the pedal pumping method with a specialist brake fluid pipe kit from Hellfrauds for

Edited March 13, 2007 by Avenger

[Galaxy_Quest]

Bump... need help folks <_<

[RADIOTWO]

so how exactly do you push the pistons back without clamping off the flexi lines and releasing the excess fluid via the bleed nipples? do you advise back flushing the fluid through the ABS valve block to the reservoir and allow it to over flow?

 

to quote Haynes, not the most technicall of manuals but it does the job

THE ABS UNIT CONTAINS HYDRAULIC COMPONENTS THAT ARE VERY SENSITIVE TO IMPURITIES IN THE BRAKE FLUID, EVEN THE SMALLEST PARTICLES CAN CAUSE THE SYSTEM TO FAIL THROUGH BLOCKAGE. THE PAD RETRACTION METHOD DESCRIBED HERE PREVENTS DEBRI IN THE BRAKE FLUID EXPELLED FROM THE CALIPER FROM BEING PASSED BACK INTO THE ABS HYDRAULIC UNIT

 

the method mentioned is to clamp off the lines and undo the bleed nipples to allow the fluid to exit the caliper as you retract the piston

Wolfie

 

First of all you don't clamp off the hozes, just push the pistons back in, the fluid will just go back into the reseroir, if you do just one at once then the fluid will only go back to the level as if the pads were new.

 

if you have not opened the system then there will not be any debri in the system.

 

when ever I have changed pads I have never had to bleed the system, and never had a problem

 

Radiotwo

[Galaxy_Quest]

First of all you don't clamp off the hozes, just push the pistons back in, the fluid will just go back into the reseroir, if you do just one at once then the fluid will only go back to the level as if the pads were new.

 

if you have not opened the system then there will not be any debri in the system.

 

when ever I have changed pads I have never had to bleed the system, and never had a problem

 

Radiotwo

 

Cheers Radio,

 

"Just push the pistons in"

 

Heres the thing.. to move the pistons in requires quite a bit of force so either (1) you need a piston pushing specialist tool or (2) gentle tapping on the old brake pads onto the piston with a little pin hammer or the like to force it back.... it would be great if you could force the brake fluid into the reservoir but if not, then opening the bleed nipple (with bleed pipes connected) is a good way to express the brake fluid which is displaced by the piston.

 

How would you suggest pushing the pistons back in?

 

(For the record, Ford TIS suggests a 12-014 Cailper Piston Expander)

 

... hence what Wolfie says does make a little bit of sense.

 

If you have the tools it is better as you say NOT to risk allowing air or worse still debris into the system via the calipers / bleed nipple. According to the Ford TIS manual you take apart the whole system! Happy to post excerpts from the TIS if necessary.

 

Either way, when I changed the pads I decided to connect the brake bleeding pipes to allow for the expelling of displaced brake fluid. It takes less than 5 mins per corner to then additionally bleed the brake... the old fluid really is baby nappy green so its no bad thing.

 

Does anyone know about the brake fluid circuits.. .can you do each corner independantly, or fronts then rears or diagonals?

 

Pressure is still low but the system IS NOT failing, the problem should not, I hope, be debris <_<

Edited March 13, 2007 by Avenger

[MadBaz]

You must undo the bleed nipple when you push back the pistons or you risk flipping the ABS seals, also these seals are manufactured to very fine tolerances (less than 10 microns in some cases) and if any dirt goes passed them it will damage them.

 

The brake cuircuit is diagonal on mk1's.

 

EDIT: I recommend using a pressure bleeding kit, it makes the job hell of a lot easier.

Edited March 13, 2007 by MADBAZ

[RADIOTWO]

First of all you don't clamp off the hozes, just push the pistons back in, the fluid will just go back into the reseroir, if you do just one at once then the fluid will only go back to the level as if the pads were new.

 

if you have not opened the system then there will not be any debri in the system.

 

when ever I have changed pads I have never had to bleed the system, and never had a problem

 

Radiotwo

 

Cheers Radio,

 

"Just push the pistons in"

 

Heres the thing.. to move the pistons in requires quite a bit of force so either (1) you need a piston pushing specialist tool or (2) gentle tapping on the old brake pads onto the piston with a little pin hammer or the like to force it back.... it would be great if you could force the brake fluid into the reservoir but if not, then opening the bleed nipple (with bleed pipes connected) is a good way to express the brake fluid which is displaced by the piston.

 

How would you suggest pushing the pistons back in?

 

(For the record, Ford TIS suggests a 12-014 Cailper Piston Expander)

 

... hence what Wolfie says does make a little bit of sense.

 

If you have the tools it is better as you say NOT to risk allowing air or worse still debris into the system via the calipers / bleed nipple. According to the Ford TIS manual you take apart the whole system! Happy to post excerpts from the TIS if necessary.

 

Either way, when I changed the pads I decided to connect the brake bleeding pipes to allow for the expelling of displaced brake fluid. It takes less than 5 mins per corner to then additionally bleed the brake... the old fluid really is baby nappy green so its no bad thing.

 

Does anyone know about the brake fluid circuits.. .can you do each corner independantly, or fronts then rears or diagonals?

 

Pressure is still low but the system IS NOT failing, the problem should not, I hope, be debris <_<

 

Hi Again,

 

First tell me ! Do you have to screw the pistons in, or do they just push in? (yes they are hard)

 

If you need to screw them in, then yes you will need a tool,but if it is for the front, there is no need to screw them in, so remove the pads, turn the pads round, and get a "G" clamp and slowly screw the piston(s) back in.(don't use a hammer as that will poss mean they will not go in streight and jam.

 

As you push them in, and the fluid will go back into the master cylinder tank,(don't forget as the pads wear the fluid level drops)

 

As per the circuits as you put it, there are split circuits but not sure, but the rule of thumb Begin at the corner furthest from the driver and proceed in order toward the driver. (Right rear, left rear, right front, left front.)

 

The master cylinder is divided internally into two sections, each of which pressurizes a separate hydraulic circuit. Each section supplies pressure to one circuit. Passenger vehicles typically have either a front/rear split brake system or a diagonal split brake system.

 

A front/rear split system uses one master cylinder section to pressurize the front slave cylinders, and the other section to pressurize the rear slave cylinders. A split circuit braking system is now required by law in most countries for safety reasons; if one circuit fails, the other circuit can stop the vehicle.

 

The diameter and length of the master cylinder has a significant effect on the performance of the brake system. A larger diameter master cylinder delivers more hydraulic fluid to the slave cylinders, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. A smaller diameter master cylinder has the opposite effect.

 

 

Radiotwo

[Galaxy_Quest]

Hi Again,

 

First tell me ! Do you have to screw the pistons in, or do they just push in? (yes they are hard)

 

If you need to screw them in, then yes you will need a tool,but if it is for the front, there is no need to screw them in, so remove the pads, turn the pads round, and get a "G" clamp and slowly screw the piston(s) back in.(don't use a hammer as that will poss mean they will not go in streight and jam.

 

As you push them in, and the fluid will go back into the master cylinder tank,(don't forget as the pads wear the fluid level drops)

 

As per the circuits as you put it, there are split circuits but not sure, but the rule of thumb Begin at the corner furthest from the driver and proceed in order toward the driver. (Right rear, left rear, right front, left front.)

 

The master cylinder is divided internally into two sections, each of which pressurizes a separate hydraulic circuit. Each section supplies pressure to one circuit. Passenger vehicles typically have either a front/rear split brake system or a diagonal split brake system.

 

A front/rear split system uses one master cylinder section to pressurize the front slave cylinders, and the other section to pressurize the rear slave cylinders. A split circuit braking system is now required by law in most countries for safety reasons; if one circuit fails, the other circuit can stop the vehicle.

 

The diameter and length of the master cylinder has a significant effect on the performance of the brake system. A larger diameter master cylinder delivers more hydraulic fluid to the slave cylinders, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. A smaller diameter master cylinder has the opposite effect.

 

 

Radiotwo

 

Thanks All,

 

Thanks for the copy and paste radio. Nothing new there, nor anything that helps me with a diagnostic.

 

I thought it may be diagonally split - cheers. The Gal is a Mk2 NOT a Mk1.

[buford_t_justice]

First tell me ! Do you have to screw the pistons in, or do they just push in? (yes they are hard)

 

 

The rear pistons screw back in. The front pistons push in.

[Guest wolfie]

Hi Again,

 

First tell me ! Do you have to screw the pistons in, or do they just push in? (yes they are hard)

 

If you need to screw them in, then yes you will need a tool,but if it is for the front, there is no need to screw them in, so remove the pads, turn the pads round, and get a "G" clamp and slowly screw the piston(s) back in.(don't use a hammer as that will poss mean they will not go in streight and jam.

 

As you push them in, and the fluid will go back into the master cylinder tank,(don't forget as the pads wear the fluid level drops)

 

either way push or screw? you need to clamp the flexi line and open the bleed nipple to release the pressure and allow the fluid to escape, allowing the fluid to back flush any crap in the lines back through the ABS valve block is a dumb arse move

[RADIOTWO]

either way push or screw? you need to clamp the flexi line and open the bleed nipple to release the pressure and allow the fluid to escape, allowing the fluid to back flush any crap in the lines back through the ABS valve block is a dumb arse move

 

Hello Wolfie

 

So where is the "crap" as you put it comming from?

 

Radiotwo

[littledaz]

For what it's worth,

 

Before pressing piston back into cylinder with piston resetting tool, draw off brake fluid from brake fluid reservoir. Otherwise, particularly if reservoir has been topped up, fluid will overflow and cause damage

 

The above quote is from VW workshop manual for Sharan. Surely, if the manufacturer sees it as OK to push the piston back allowing fluid to re-enter the reservoir, then it must not cause any damage internally. Consider the action of pressing and releasing the brake pedal, the fluid is moving back and forth in the system, admittedly not to the extent of pushing the piston fully home.

 

Ask any garage, I bet they don't open the nipples to push the piston back!

Edited March 13, 2007 by littledaz

[Galaxy_Quest]

either way push or screw? you need to clamp the flexi line and open the bleed nipple to release the pressure and allow the fluid to escape, allowing the fluid to back flush any crap in the lines back through the ABS valve block is a dumb arse move

 

Hello Wolfie

 

So where is the "crap" as you put it comming from?

 

Radiotwo

 

 

Radio,

 

I assume u havent flushed brake lines for a while then. You will be aware that when u expel the fluid it is a murkey green / black colour... not the clear yellow colour it should be. Additionally, there is a build up of grime at the piston end. Brake fluid corrodes metal, so over time there is a build up of sediment at the piston end.

 

I dont think anyone wants this sent back round the system... especially towards a highly sensitive ABS block; but saying that it should only go a foot or so but its still not worth the risk.

 

When you fully or partially open the bleed valve the brake fluid will rather go through there than push round the system as the relative resistence is too great.

 

Either way, it seems to be a very good idea and simply a very easy option to flush the brake lines / bleed the system when you change the pads and expel a little displaced old grimey fluid. If the bleed nipple is open and the bleed tube is connected its a few seconds more. The Haynes and TIS manuals seem to agree on this as part of brake replacement or am i wrong on this?

 

So the question is, I may well have forced the rear pistons back in when they were screw ones... but no more force than was required on the fronts... and they went in ok.

 

So looking at post #1, whats the possible reasons for a loss in pressure once all bled and reconnected?

[Dave-G]

I've been pushing back my pistons for over 40 years. Untill I got ABS cars - using a small vice to do the job. I now use a combination screw/press.

 

I'm not saying "don't do it" but I have never released the nipples when pushing the fluid out of the brake caliper/cylinder. I have never had a problem with brakes after doing this.

[RADIOTWO]

So looking at post #1, whats the possible reasons for a loss in pressure once all bled and reconnected?

 

To answer the question Avenger, You have air in the system !

 

it is poss lodged somewhere and that is why the pedel is spongy.

 

but as littledaz & Dave say, they don't do it at a garage, and as far as going back into the ABS system, the

amount of fluid is only small, it would only go back up the pipe about 6" at the most, so won't get to the abs

bit, even with abs systems I have pushed back the pistons with the nipple closed, and then you don't have

the problems you have.

 

Just a point, which I did not read, but did you take the piston right out?

 

Radiotwo

[Galaxy_Quest]

So looking at post #1, whats the possible reasons for a loss in pressure once all bled and reconnected?

 

To answer the question Avenger, You have air in the system !

 

it is poss lodged somewhere and that is why the pedel is spongy.

 

but as littledaz & Dave say, they don't do it at a garage, and as far as going back into the ABS system, the

amount of fluid is only small, it would only go back up the pipe about 6" at the most, so won't get to the abs

bit, even with abs systems I have pushed back the pistons with the nipple closed, and then you don't have

the problems you have.

 

Just a point, which I did not read, but did you take the piston right out?

 

Radiotwo

 

Hi radio,

 

I pushed the piston as far out as it would go... in fairness I didnt check if this was out 100%, just out as much as I could reasonably get it.

 

sounds like a pain the a*se jon, but looks like I will have to bleed the lines again one by one starting front left and going in a circle... front right, rear right....etc

Edited March 14, 2007 by Avenger

[RADIOTWO]

Is there two of you doing the job, or just you(on you own)?

 

Radiotwo

[Galaxy_Quest]

Is there two of you doing the job, or just you(on you own)?

 

Radiotwo

 

Always have the mrs handy and lad gets in after 3pm.

 

Ive had to take the motor for an MOT retest today... last day. The brakes are very firm for first couple of mins after start up but loses a little pressure about 5 mins after. I think a thorough bleed will do it when i get the Gal back... Ford TIS seems to state that bleed fronts one after another, then the rears one after another.

 

If theres any other suggestions I'm all ears !

[RADIOTWO]

Is there two of you doing the job, or just you(on you own)?

 

Radiotwo

 

Always have the mrs handy and lad gets in after 3pm.

 

Ive had to take the motor for an MOT retest today... last day. The brakes are very firm for first couple of mins after start up but loses a little pressure about 5 mins after. I think a thorough bleed will do it when i get the Gal back... Ford TIS seems to state that bleed fronts one after another, then the rears one after another.

 

If theres any other suggestions I'm all ears !

Hi

 

No offence to your (mrs) but you need someone with a lot of foot presure for the brake pedal,you need to pump about 4/5 times (hard), but please when (as mentioned in the coppied text) you need to hold down the pedal till the valve is closed.

 

Hope it passes the MOT But if the pedal is spungy they might not pass it !

 

Good luck

 

Radiotwo

[Galaxy_Quest]

Hi

 

No offence to your (mrs) but you need someone with a lot of foot presure for the brake pedal,you need to pump about 4/5 times (hard), but please when (as mentioned in the coppied text) you need to hold down the pedal till the valve is closed.

 

Hope it passes the MOT But if the pedal is spungy they might not pass it !

 

Good luck

 

Radiotwo

 

Hi Radio,

 

No offence taken; the Mrs is a very strong woman so i have no concerns there, but my 14 yr old lad is on the slight side. I think a thorough re-bleed is needed when i get the car back tomorrow.

 

<_<

[tbag]

Hi all, just done my brakes using a one man kit from halfords.I got the wife to pump while i sorted out the nipple end.Several pumps were needed till new fluid appeared then i tightened up the nipple,We did the rear ones, then it rained, so left the front till the weekend.The pedal went a bit soft also went down further before biting. So the next time i got the wife to pump 4 times and hold pedal down on last stroke then tighten up the nipple.Done the fronts, now we have superb brakes with new fluid.