75 Tourer Brake Pedal goes to floor

Alisdair · 25th April 2007, 22:30

75 Tourer (Jan 2004) CDTi with Traction Control (33,000 Miles).

Brake wear warnibg light came on at the weekend and have now replaced the front and rear pads with replacements made by Quinton Hazel.

Reading the Rover Workshop Manual made the mistake of releasing the bleed screw to retract the Piston on the front offside and possibly allowed some air into system. On all other wheels retracted the calliper piston without releasing the bleed nipple. Initially brakes appeared soft but have since bled each of the wheels.

However I am getting a strange effect if I keep pressing the brake pedal when stopped. The pedal appears to very slowly sink to the floor.

There are no visible fluid leaks have rechecked each wheel calliper, hoses and pipes. The brake fluid level appears to remain at the MAX level.

Help...anyone experienced this problem, is this a mster cylinder failure? if so why both circuits or is this simply an issue with the pads needing to bed in.

JohnDotCom · 25th April 2007, 22:35

Alisdair to the Club.
Sounds like there could still be air in the System, have you tried rebleeding the system?
Someone else will be along shortly with more help.

Alisdair · 25th April 2007, 22:59

Yes, I went round every calliper and re-bled the whiole system put something like 500ml of new fluid through it.

The brakes appear to work OK, the pedal just ever so slowlky sinks to the floor (with the engine running and with servo power) over a period of minutes after car has stopped. When engine is stopped and no servoi power it doensnt seem to go to the floor. I cannot press it hard enough.

I will need to bed the brakes in a bit tomorrow.

Seems strange is it possible to blow the master cylinder seals????

I think I will open up the bulkhead access panels tomorrow to check for leaks around the master cylinder.

Cuda-uk · 26th April 2007, 21:34

Hi Alisdair

It sounds like you have damaged the seals inside the master cylinder and the brake fluid is creeping past them as you keep the pressure applied. This normally happens when the brake pedal is depressed to it limit normally while bleeding brakes, this is why most garages now use a vacuum system to remove air from the braking system. Sorry but it sounds like you will need to get some new seals for the master cylinder if available if not a new master cylinder.

Alisdair · 26th April 2007, 22:09

Hi Cuda-UK

I am coming to that conclusion, seems strange that you can damage the seals simply by pressing the pedal. However there must be considerable pressure applied if you press the pedal hard with the servo operating.

I have looked at the MG-Rover parts catalogue but there are no seals shown for the master cylinder, they only show a repair kit for the brake callipers.

Unless someone knows where they can be found.

I road tested the car today to bed in the new pads and the brakes work OK no softness. ABS also working OK when testing on a loose surface.

Unless someone knows anything different I will replace the master cylinder at the weekend and bleed the brake system with an Ezi Bleed pressure system. Just a nuisance, I wonder if that is why the MG-Rover workshop manual instructs you to open the bleed nipple when pushing back the calliper piston. Is it possible that pushing fluid back throiugh the master cylinder damages the seals.

Cuda-uk · 26th April 2007, 22:18

Normally the reason for opening the bleed nipples on the calipers is to stop the brake fluid from over filling the master cylinder, as people tend to top up the m/c as the brake pads wear. It also removes the bad portion of the brake fluid. As the calipers are the lowest point (normally) of the braking system this tends to be the area water and dirt end up, and the last place you want water in a brake system is in the calipers. HTH

Cuda-uk · 26th April 2007, 22:19

Quote:

Originally Posted by Alisdair

Is it possible that pushing fluid back throiugh the master cylinder damages the seals.

Very unlikely

rovermech · 27th April 2007, 11:11

When fitting new pads and you have to press the pistons in to fit the new pads. On a ABS system I always open the bleed screw to release the fluid, pushing the fluid back through the system can damage the seals in the m/c and the ABS.
But because you have changed all the pads I would bed them in first and see how it goes.

Cuda-uk · 27th April 2007, 19:57

Quote:

Originally Posted by rovermech

pushing the fluid back through the system can damage the seals in the m/c and the ABS.
But because you have changed all the pads I would bed them in first and see how it goes.

I stand corrected

Alisdair · 28th April 2007, 21:43

Thanks "rovermech" for your advice. I have obtained a good master cylinder but I will wait to I get a Gunsons eezi-bleed before I change the unit. I hear what you are saying about the ABS as well however as that is a sealed unit with no apparent leaks where would the fluid go? I would have thought the pressure would still hold even if the ABS unit was damaged. I am coming to the comclusion that you now cannot bleed the brakes on a dual circuit ABS vehicle without a vacum or pressure bleeder. For DIY a pressure bleeder is likely the easier device as you do not need an air supply. I will keep you posted of developments.

25th April 2007, 22:30	#1
Alisdair Newbie Rover 75 Tourer Join Date: Apr 2007 Location: Glasgow Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	75 Tourer Brake Pedal goes to floor 75 Tourer (Jan 2004) CDTi with Traction Control (33,000 Miles). Brake wear warnibg light came on at the weekend and have now replaced the front and rear pads with replacements made by Quinton Hazel. Reading the Rover Workshop Manual made the mistake of releasing the bleed screw to retract the Piston on the front offside and possibly allowed some air into system. On all other wheels retracted the calliper piston without releasing the bleed nipple. Initially brakes appeared soft but have since bled each of the wheels. However I am getting a strange effect if I keep pressing the brake pedal when stopped. The pedal appears to very slowly sink to the floor. There are no visible fluid leaks have rechecked each wheel calliper, hoses and pipes. The brake fluid level appears to remain at the MAX level. Help...anyone experienced this problem, is this a mster cylinder failure? if so why both circuits or is this simply an issue with the pads needing to bed in.

25th April 2007, 22:59	#3
Alisdair Newbie Rover 75 Tourer Join Date: Apr 2007 Location: Glasgow Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Yes ReBled whole system Yes, I went round every calliper and re-bled the whiole system put something like 500ml of new fluid through it. The brakes appear to work OK, the pedal just ever so slowlky sinks to the floor (with the engine running and with servo power) over a period of minutes after car has stopped. When engine is stopped and no servoi power it doensnt seem to go to the floor. I cannot press it hard enough. I will need to bed the brakes in a bit tomorrow. Seems strange is it possible to blow the master cylinder seals???? I think I will open up the bulkhead access panels tomorrow to check for leaks around the master cylinder.

27th April 2007, 11:11	#8
rovermech Regular poster Rover 75 Saloon Join Date: Nov 2006 Location: Sheffield Posts: 54 Thanks: 1 Thanked 17 Times in 8 Posts	bleeding brakes When fitting new pads and you have to press the pistons in to fit the new pads. On a ABS system I always open the bleed screw to release the fluid, pushing the fluid back through the system can damage the seals in the m/c and the ABS. But because you have changed all the pads I would bed them in first and see how it goes.

25th April 2007, 22:35	#2
JohnDotCom * Rover 75 FaceLift Tourer CDTi 170BHP Auto ConnSE 2005 Model Starlight Silver Join Date: Nov 2006 Location: Abergele Posts: 28,735 Thanks: 0 Thanked 6 Times in 5 Posts	Alisdair to the Club. Sounds like there could still be air in the System, have you tried rebleeding the system? Someone else will be along shortly with more help.

26th April 2007, 21:34	#4
Cuda-uk Avid contributor Rover 75 Tourer Join Date: Apr 2007 Location: nr Rugby Posts: 174 Thanks: 0 Thanked 0 Times in 0 Posts	Hi Alisdair It sounds like you have damaged the seals inside the master cylinder and the brake fluid is creeping past them as you keep the pressure applied. This normally happens when the brake pedal is depressed to it limit normally while bleeding brakes, this is why most garages now use a vacuum system to remove air from the braking system. Sorry but it sounds like you will need to get some new seals for the master cylinder if available if not a new master cylinder.

26th April 2007, 22:09	#5
Alisdair Newbie Rover 75 Tourer Join Date: Apr 2007 Location: Glasgow Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Hi Cuda-UK I am coming to that conclusion, seems strange that you can damage the seals simply by pressing the pedal. However there must be considerable pressure applied if you press the pedal hard with the servo operating. I have looked at the MG-Rover parts catalogue but there are no seals shown for the master cylinder, they only show a repair kit for the brake callipers. Unless someone knows where they can be found. I road tested the car today to bed in the new pads and the brakes work OK no softness. ABS also working OK when testing on a loose surface. Unless someone knows anything different I will replace the master cylinder at the weekend and bleed the brake system with an Ezi Bleed pressure system. Just a nuisance, I wonder if that is why the MG-Rover workshop manual instructs you to open the bleed nipple when pushing back the calliper piston. Is it possible that pushing fluid back throiugh the master cylinder damages the seals.

26th April 2007, 22:18	#6
Cuda-uk Avid contributor Rover 75 Tourer Join Date: Apr 2007 Location: nr Rugby Posts: 174 Thanks: 0 Thanked 0 Times in 0 Posts	Normally the reason for opening the bleed nipples on the calipers is to stop the brake fluid from over filling the master cylinder, as people tend to top up the m/c as the brake pads wear. It also removes the bad portion of the brake fluid. As the calipers are the lowest point (normally) of the braking system this tends to be the area water and dirt end up, and the last place you want water in a brake system is in the calipers. HTH

28th April 2007, 21:43	#10
Alisdair Newbie Rover 75 Tourer Join Date: Apr 2007 Location: Glasgow Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks "rovermech" for your advice. I have obtained a good master cylinder but I will wait to I get a Gunsons eezi-bleed before I change the unit. I hear what you are saying about the ABS as well however as that is a sealed unit with no apparent leaks where would the fluid go? I would have thought the pressure would still hold even if the ABS unit was damaged. I am coming to the comclusion that you now cannot bleed the brakes on a dual circuit ABS vehicle without a vacum or pressure bleeder. For DIY a pressure bleeder is likely the easier device as you do not need an air supply. I will keep you posted of developments.