Keep loosing pedal.....

R

richarduk

Guest
I've serviced the rear breaks after the pedal went soft and went to the floor requiring an extra pump to get it hard. I thought it had fixed it as it went back to the way it should be. But it only lasted a month before started to do it again, I could not see it leaking at the rears. So I serviced the master and remote servo. I found in this case I only had to bleed it at the front to get a it back to a hard pedal so no air in the rear system but this time it only lasted a week. I've now found that it does not matter which of the three bleed locations I use either will get me back to a hard pedal, it now only lasts a few miles so is getting worse. This leads me to think the air is getting in before the system is split. I'm 100% sure that the master and remote servo is good. I have now noticed that the flex pipe from the reservoir to the master cylinder is now leaking a little, is it possible this is where the air is getting in? My only other candidate is the brake switch, this does not look as if it's leaking. If it's not these then I'm at a loss.......
 
The flexible pipe between the reservoir and the master cylinder is unlikely to be introducing air into the system because firstly it's not in the pressurised part of the system, and secondly if it was allowing air in that air would just rise up into the reservoir, not sink down into the master cyl. Next time it happens bleed the system again, starting at the rear, then NSF then OSF, and note where the air comes out, then track back through from there to see what you find. If you can bleed any point to get the pedal back then the fault will be before the system splits, so that's after the servo and although the pedal comes back bleeding any one point, there is still air in the other two.You can get air into the system without seeing leaks, it happens on diesel fuel systems, but it is less common on brakes. Chances are there is a small leak somewhere, you just need to find it.
 
I've order a new flex pipe as it needs replacing anyway, I've also order a switch. If these don't work I'm down to changing the pipes, maybe one of the connections have failed. Just as a foot note before the flex pipe started to leek I was not loosing any fluid which I thought was rather odd.
 
You aren't topping up the system with the fluid you've bled out , are you ?

There's the old trick of putting a hose clamp on each of the flex hoses in turn to see if blocking off one corner improves the pedal
 
DaveHerns said:
You aren't topping up the system with the fluid you've bled out , are you ?
Click to expand...
Never!

DaveHerns said:
There's the old trick of putting a hose clamp on each of the flex hoses in turn to see if blocking off one corner improves the pedal
Click to expand...
Yes, knew that one. :) But I've not tried to block all three off, if it still goes to the floor with all three blocked off I know the air is in the system and not the calipers. I'll have to give that a go.
 
Hi, there is another trick I was told once (although I have not tried it myself, lucky I suppose ) and that is to put brake
fluid in an oilcan and connect it to the bleed nipple by a rubber hose crack the nipple open and pump the oilcan so
pushing the fluid and air gently back up into the reservoir. This is supposed to be better as you are pushing the air
the way it wants to go. Colin
 
I've replaced the brake light switch and the hose from the reservoir that had a small split in it.

This is the old one, does look like it mayhave been leaking a bit, or is that just wishful thinking? Anyway we'll see how long the brakes last this time.

OldBrakeLightSwitch.jpg
 
If you pump the pedal so its firm,then start the car!
Giving the pedal gentle pressure whilst revving,does it gradually go to the floor,but then if you pump again firm up?
If so the seals in the servo slave need re-doing!
 
Little update: Brakes are still working perfect, must have been the light switch. :) before I changed that light switch they would last about a day.
 
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