"Floppy" brake pedal.

B

billoddie

Active Member
When I first got the car...Jan...I noticed that when applying the brakes, the pedal had a bit of a "flop" about it before the braking actuation took place. Not a lot, but enough to be irritating and maybe a little dangerous.
Inspecting it, I thought it may have been something to do with the spring...but manually making it tighter does not seem to do much.
Not sure where it is coming from, except somewhere in the actuation.
Any ideas?
Anyone have a similar experiences?
Cheers Brenten
 
Hi Brenten,

Sounds like you have air in them. Start bleeding from the rear, then n/s front and finally o/s front. That should do the trick.

Ron.
 
Yep...bled them today Ron. Just as you said.
The movement seems more mechanical... like a sense of slack in the mechanical actuation.
From the static position, there is free travel of few mm in the pivot of the pedal...like something needs adjusting or tightening. :? :?
 
Ah ha,..ok now there is adjustment in the pushrod. You can loosen the locknut and then adjust the pushrod to reduce the amount of free play. There is also the possibility that the spring in the master cylinder has broken, but see if adjusting the pushrod sorts it to your liking Brenten. There are measurments given in the workshop manual too for brake pedal height. If you don't have the manual or it doesn't say in the one you have let me know and I'll have a look in mine and post them.

Ron.
 
I reckon your right on the pushrod adjustment Ron. :)
I'll have a crack at it tommorrow.
Thanks Ron...top advice as usual
Brenten :)
 
SydneyRoverP6B said:
Ah ha,..ok now there is adjustment in the pushrod. You can loosen the locknut and then adjust the pushrod to reduce the amount of free play.
Ron.
Click to expand...

The adjustment on the pushrod isn't to remove free play, it's to set the pedal height.
 
harvey wrote,...
The adjustment on the pushrod isn't to remove free play, it's to set the pedal height.
Click to expand...

So in setting the pedal height, you remove free play. Or are you saying when setting the pedal height it removes no free play prior to compressing the spring in the master cylinder?

Ron.
 
SydneyRoverP6B said:
harvey wrote,...
The adjustment on the pushrod isn't to remove free play, it's to set the pedal height.
Click to expand...

So in setting the pedal height, you remove free play. Or are you saying when setting the pedal height it removes no free play prior to compressing the spring in the master cylinder?

Ron.
Click to expand...


What I'm saying is that there is a set height for the pedal, and that's nothing to do with whether there is free play or not. If the pedal height is correctly set, don't go messing around with it in an effort to remove free play elsewhere.
 
HI, I agree with Harvey. If the spring in the master cylinder has pushed the rod to the end stop
adjusting the pedal height by moving the pedal along the push rod will not remove any play in
the pedal fulcrum point which is where I think the problem lies.

Colin
 
Hi all,

My brake pedal action has been unsatisfying since I got the car. After a bit of mucking about before my inspection I got some help from my brakes specialist today. He refitted an old piston I had with old seals in the relief valve assembly, and that helped with the notchy booster action (it would come on with a jolt). However, there's still a bit of travel still before the piston is pushed out and the booster comes on. Is there supposed to be any? I am quite confident that there's no air in the system, but at some point this year I'll have fluid changed and the brakes bled by this guy, who knows the system very well.

Meanwhile I'm doing what's not been recommended here, adjusting the pushrod up to the point where the brakes bind and then back off a little. The pedal feels better, but nowhere near as firm as single-circuit cars I've driven. What do I risk by doing this?
 
Tor said:
Meanwhile I'm doing what's not been recommended here, adjusting the pushrod up to the point where the brakes bind and then back off a little. The pedal feels better, but nowhere near as firm as single-circuit cars I've driven. What do I risk by doing this?
Click to expand...

If you mean the pushrod from the master cylinder to the pedal, as I've said before, that's not there to remove freeplay in the pedal, it's purely to set the pedal height and if you start messing aound with it for other reasons you may find that
DaveHerns said:
The brakes may lock on or drag
Click to expand...
.
 
OK cheers. That's as I guessed it would be. The thing that remains to ask is, given that there's an inch of pedal travel before the booster kicks in, is that definitely air in the fluid? The pedal never sinks or anything. It travels a bit on application but remains where I put it.
 
It could be air in the system, but rapidly pumping the pedal should get rid of that, albeit only on a temporary basis, or it could be the pads are being backed off between applications for some reason. Have you set the pedal height?
 
Pedal height - well ... I've adjusted it to reduce pedal travel (mentioned in my Projects thread), so at the moment the pedal-master pushrod won't return all the way to the stop. A quick double-pump on the pedal takes up travel as you say and firms things up well.
 
I've never bled the dual systems, but have heard they can be a pain to do, although whether that's the fault of the system or the people doing the bleeding I couldn't possibly say, but I can't ever remember having problems doing other dual line systems. The only thing you have to be careful of is the PDWV as the shuttle ends up in the wrong place. Pull back the carpet and set the distance between the floor and the bottom of the pedal to either 6.5" if it's an auto, or 6 + 7/8" if it's a manual. (or it's an auto and you feel like it.)
 
I think I get the picture, and the PDWV shuttle sounds like what my local guy said he would arrest when bleeding a P6 with a dual circuit system. Can I ask you to describe though: My brake pedal still travels some before the boost comes on. With zero air bubbles in the fluid, and everything being as Rover intended, will the very first movement of the pushrod actuate the relief-valve piston or is that connection mechanical?
 
If by that you mean should you get servo boost from the point you operate the pedal I'd say yes once any free play is taken up, and most of the free play should disappear once the pedal height is set, and it's fully bled, but as I said previously I've never had anything to do with that system, and nor am I ever likely to, TBH, so all I could do is have a look at the schematic in the book, work out how it's supposed to function, and then try and work out what could be causing the fault you've got.

All of the advice I give on here is from having done the jobs and rectified the faults, but this is the exception, so puts me at a disadvantage. You need someone really familiar with the system, and that's pretty unlikely, because although there will be people who've worked on them, they won't have done hundreds of them, all with different faults, to gain the experience required to go straight to cause of the problem, as there just aren't enough of them out there, and there weren't even back in the day.

Set the pedal height, and then if you're still struggling I'll have a sit down with the book.
 
harveyp6 said:
If by that you mean should you get servo boost from the point you operate the pedal I'd say yes once any free play is taken up, and most of the free play should disappear once the pedal height is set, and it's fully bled
Click to expand...
OK great... for years I've tried to accept that the dual system is just "softer" that way. I'm (tentatively) glad it's (apparently) not the case...
harveyp6 said:
Set the pedal height, and then if you're still struggling I'll have a sit down with the book.
Click to expand...
I'll set the pedal height - but also get it bled again. Then I'll report back. Thanks a tonne!
 
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