75 Tourer Brake Pedal goes to floor - Page 2

rovermech · 29th April 2007, 20:04

I have never had any problem with bleeding ABS brakes by the foot pedel method, I have the engine running to give a signal to the ABS and then bleed
1 o/s/f 2 n/s/f 3 o/s/r 4 n/s/r always by opening the bleed nipple.
If you force the fluid back through the system you risk reversing a seal in the ABS or m/c

Mr.Ian · 29th April 2007, 20:26

Does the rover 75 only have 4 bleed screws??
Only asking as i've bled brakes before (at each wheel) and found there's still air trapped in the system, found on a few cars they have a bleed screw on a load valve also (that cuts pressure to the rear brakes during light load conditions).
Just a thought

Owen · 11th March 2009, 18:52

I too have the same problem. I also replaced the brake pads, then fitted a new master cylinder, bled the system twice and now have a rock hard pedal when the engine is off and no servo, which would indicate to me that all the seals should be ok. However, when the engine starts and the servo kicks in, while the brakes work, it is possible to press the pedal to the floor as if the master cylinder is faulty! The handbrake warning light is now also staying on and it is not the handle at fault and I am occasionally getting the short brake fault message. I have road tested the brakes at 50 - 60 mph and they and the ABS certainly work. Confused!!!!

StevenWilliams · 11th March 2009, 19:06

You didn't do anything else when you were working on the brakes did you?
I always thought the servo used some of the vacuum generated by the engine to assist the braking. If the vacuum is venting to air somewhere you will loose some of the servo assistance.
I know this can happen on some cars as it did with my Honda a while back but I don't know about the Rover/MG.

On the Honda I had a broken breather hose in the engine bay. Hardly any affect to the engine but massive to the brakes.

Owen · 11th March 2009, 19:53

I seem to have too much servo assistance!

T-Cut · 11th March 2009, 20:03

The sinking brake pedal phenomenon has been discussed several times and no logical explanation has been forthcoming. Here's an example thread: http://www.the75andztclub.co.uk/foru...inking+feeling

However, the effect is so widely reported, I've come to the conclusion it's actually normal. Provided the pedal is hard and unyielding with the engine off, the slow sink under servo assistance seems to be something these cars do. I don't think it's unique to 75s/ZTs either. Some people report similar behaviour in other makes. I don't believe there's a connection with brake bleeding. I think the phenomenon gets reported when people are servicing the brakes. At other times the effect is simply not noticed.

David Lawrence · 11th March 2009, 20:34

Can it be common to diesels because it uses a pump to create servo vacuum rather than engine vacuum. My impression is that the pedal sinks a bit further after the vacuum starts to build up again, after you've invariably emptied the servo vacuum during bleeding.
It doesn't actually get as far as the floor does it? And you certainly don't ever need to push the pedal that far down to effectively stop the car from speed, or indeed pass an MOT brake test, so I also concluded the phenomenon was "Normal"

T-Cut · 11th March 2009, 21:47

Quote:

Originally Posted by David Lawrence

Can it be common to diesels because it uses a pump to create servo vacuum rather than engine vacuum.

The source of vacuum isn't relevant to the phenomenon. It does appear to be servo related, but not model dependant. No, the pedal never goes right to the floor, but far enough to make you worry when first found. I worried about it at first, but I'd forgotten about it before reading this latest thread. My 1.8T does it, but the braking is superb.

Lates · 11th March 2009, 22:09

Quote:

Originally Posted by T-Cut

The source of vacuum isn't relevant to the phenomenon. It does appear to be servo related, but not model dependant. No, the pedal never goes right to the floor, but far enough to make you worry when first found. I worried about it at first, but I'd forgotten about it before reading this latest thread. My 1.8T does it, but the braking is superb.

Agree, the first few times you come across this, its a worry.

disclaimer - this is only my opinion btw whilst discussing safety related concerns.

moonstoneboy · 12th March 2009, 07:27

Do not know what the internals of a 75 master cylinder are but on the older type of cylinder, when the pedal is up the piston in the cylinder is pushed back by a spring allowing passage of fluid from the reservoir in to the chamber. When the brakes are applied the piston moves forward and there is a seal that prevents the fluid being pushed back in to the reservoir so that the only place it has to go is along the lines to the wheels. This seal can fail thus alowing the fluid back in to the reservoir under braking. Hence this does not give rise to any reduction of the level in the reservoir.

If the main seals on the piston fail then fluid would leak past this seal and drip down inside the car with an on-going lowering of the level in the reservoir.

Paul

29th April 2007, 20:04	#11
rovermech Regular poster Rover 75 Saloon Join Date: Nov 2006 Location: Sheffield Posts: 54 Thanks: 1 Thanked 17 Times in 8 Posts	ABS Brakes I have never had any problem with bleeding ABS brakes by the foot pedel method, I have the engine running to give a signal to the ABS and then bleed 1 o/s/f 2 n/s/f 3 o/s/r 4 n/s/r always by opening the bleed nipple. If you force the fluid back through the system you risk reversing a seal in the ABS or m/c

11th March 2009, 18:52	#13
Owen Newbie Rover 75 CTDi Tourer Join Date: Feb 2009 Location: Aberdeenshire Posts: 10 Thanks: 0 Thanked 0 Times in 0 Posts	Soft brake pedal I too have the same problem. I also replaced the brake pads, then fitted a new master cylinder, bled the system twice and now have a rock hard pedal when the engine is off and no servo, which would indicate to me that all the seals should be ok. However, when the engine starts and the servo kicks in, while the brakes work, it is possible to press the pedal to the floor as if the master cylinder is faulty! The handbrake warning light is now also staying on and it is not the handle at fault and I am occasionally getting the short brake fault message. I have road tested the brakes at 50 - 60 mph and they and the ABS certainly work. Confused!!!!

11th March 2009, 19:06	#14
StevenWilliams This is my second home Rover 75 Saloon 2.5 V6 British Racing Green. 81,000 miles and counting Join Date: Apr 2008 Location: Crawley, West Sussex Posts: 6,183 Thanks: 0 Thanked 2 Times in 2 Posts	You didn't do anything else when you were working on the brakes did you? I always thought the servo used some of the vacuum generated by the engine to assist the braking. If the vacuum is venting to air somewhere you will loose some of the servo assistance. I know this can happen on some cars as it did with my Honda a while back but I don't know about the Rover/MG. On the Honda I had a broken breather hose in the engine bay. Hardly any affect to the engine but massive to the brakes. __________________ [SIGPIC][/SIGPIC] Rover 75 2.5 2000 Club SE. British Racing Green. MEMBER NUMBER: MMMDCCXXVI Looking for: 7 seater

29th April 2007, 20:26	#12
Mr.Ian Avid contributor Rover 75 Tourer Join Date: Mar 2007 Location: Lancashire Posts: 126 Thanks: 0 Thanked 0 Times in 0 Posts	Does the rover 75 only have 4 bleed screws?? Only asking as i've bled brakes before (at each wheel) and found there's still air trapped in the system, found on a few cars they have a bleed screw on a load valve also (that cuts pressure to the rear brakes during light load conditions). Just a thought

11th March 2009, 19:53	#15
Owen Newbie Rover 75 CTDi Tourer Join Date: Feb 2009 Location: Aberdeenshire Posts: 10 Thanks: 0 Thanked 0 Times in 0 Posts	I seem to have too much servo assistance!

11th March 2009, 20:03	#16
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	The sinking brake pedal phenomenon has been discussed several times and no logical explanation has been forthcoming. Here's an example thread: http://www.the75andztclub.co.uk/foru...inking+feeling However, the effect is so widely reported, I've come to the conclusion it's actually normal. Provided the pedal is hard and unyielding with the engine off, the slow sink under servo assistance seems to be something these cars do. I don't think it's unique to 75s/ZTs either. Some people report similar behaviour in other makes. I don't believe there's a connection with brake bleeding. I think the phenomenon gets reported when people are servicing the brakes. At other times the effect is simply not noticed.

11th March 2009, 20:34	#17
David Lawrence This is my second home Rover 75 CDT-2001 Join Date: Jan 2009 Location: Wrexham, North Wales Posts: 3,606 Thanks: 195 Thanked 606 Times in 501 Posts	Can it be common to diesels because it uses a pump to create servo vacuum rather than engine vacuum. My impression is that the pedal sinks a bit further after the vacuum starts to build up again, after you've invariably emptied the servo vacuum during bleeding. It doesn't actually get as far as the floor does it? And you certainly don't ever need to push the pedal that far down to effectively stop the car from speed, or indeed pass an MOT brake test, so I also concluded the phenomenon was "Normal"

12th March 2009, 07:27	#20
moonstoneboy Posted a thing or two Rover 75 Connoisseur SE CDT Tourer - naturally in Moonstone Green Join Date: Oct 2007 Location: Surrey - near Gatwick Airport Posts: 1,316 Thanks: 0 Thanked 3 Times in 3 Posts	Do not know what the internals of a 75 master cylinder are but on the older type of cylinder, when the pedal is up the piston in the cylinder is pushed back by a spring allowing passage of fluid from the reservoir in to the chamber. When the brakes are applied the piston moves forward and there is a seal that prevents the fluid being pushed back in to the reservoir so that the only place it has to go is along the lines to the wheels. This seal can fail thus alowing the fluid back in to the reservoir under braking. Hence this does not give rise to any reduction of the level in the reservoir. If the main seals on the piston fail then fluid would leak past this seal and drip down inside the car with an on-going lowering of the level in the reservoir. Paul