mistergrumpy
|
| posted on 15/6/09 at 06:53 PM |
|
|
Soft To No Brakes
A bit of a funny one but I'm after some discussion/suggestions/diagnoses with my brakes.
I'll say first that Turbo has already suggested a residual pressure valve and I'm grateful for the help there but just wanted to maybe
look a bit deeper as the consensus seems that people don't like these valves.
Anyhow, here's the problem. I have Sierra brakes and a Fiesta MK.1 MC (0.7 or 0.75). I have two lines to the front and one line to the rear with
a bias valve in it. I also drilled into the valve to bleed it and have a stainless bolt in it to seal it. When I bleed the brakes, the pedal is hard
and good but the problem is that when I leave it overnight it goes very soft almost so it hits the bulkhead, but not quite. Another day and it's
gone and will hit the bulkhead. I put the handbrake on last night when the pedal had gone to the soft stage and it seems to be holding there (though
I'm not sure if it would've dropped or held had it been fully hard) and not going to the stage where it'll hit the bulkhead.
Any suggestions or ideas gratefully welcomed.
|
|
|
|
|
britishtrident
|
| posted on 15/6/09 at 07:04 PM |
|
|
I have only ever encountered similar symptoms once before and that was eventually traced to a defective flexible hose.
You need to do some detective work establish which circuit the problem is with --- next time you bleed the brakes bleeding only one circuit or better
still try bleed only one caliper then test to see you get a solid pedal before moving on to the next caliper.
[Edited on 15/6/09 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
mistergrumpy
|
| posted on 15/6/09 at 07:08 PM |
|
|
In what way was it defective? Leaking?
|
|
|
britishtrident
|
| posted on 15/6/09 at 07:12 PM |
|
|
quote:
Originally posted by mistergrumpy
In what way was it defective? Leaking?
It was drawing air in -- no visible fluid leak to the outside world.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
mistergrumpy
|
| posted on 15/6/09 at 07:19 PM |
|
|
Hmm. So if I bind the ends up it might give an indication of things.
Cheers BT
Any other ideas?
|
|
|
rusty nuts
|
| posted on 15/6/09 at 07:22 PM |
|
|
Bolt sealing the valve?? Not a good idea IMHO . Might be worth getting a couple of blanking plugs and fitting to one brake curcuit at a time to
isolate which part of the braking system is at fault. When bleeding which curcuit has the most air in?
|
|
|
mistergrumpy
|
| posted on 15/6/09 at 07:27 PM |
|
|
It's a stainless dome head. What could I use instead?
If I use blanking plugs I'd have to drain then seal and re fill and repeat again for the other circuits right?
As for air I tried the front offside first I think which bubbled a fair amount out quickly, then stopped. The n/s had nowt and then onto the rear
offside which had a bit then the n/s nowt.
|
|
|
austin man
|
| posted on 15/6/09 at 08:17 PM |
|
|
have you got sierra discs on the rear ?? had a similar problem on an Indy it was something to do with the height of the bleed nipple on the rear
caliper had br lowered if I recal correctl to allo all air to travel out.
It could also be the seal in the master cylinder drawing in air check the rear of the cylinder the sierra units seem prone to leaking. Just had to
replace mine. Other things are check all connections and the bolt doesnet seem a good idea either as the pitch of the thread may be too coarse
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
|
|
|
mistergrumpy
|
| posted on 15/6/09 at 08:24 PM |
|
|
Yeah discs on the rear with the nipple on the top because air will travel up and so will escape via the nipple. I have removed the caliper anyway and
turned it all directions and jacked the front end so it's lower, I don't think it's that. The bleed screw on the bias valve seems to
be the concensus then. I cut the thread into it myself so it should be a good fit. I'll trial some PTFE and maybe a copper washer or summat.
Oh, its a Fiesta MC not a Sierra one and it was new old stock.
|
|
|
adithorp
|
| posted on 16/6/09 at 12:30 PM |
|
|
So what is sealing the bias bleed screw? If your seal is just the bolt head then you need a copper washer on there. Might still be something else but
I'd start there. PTFE isn't recomended for brakes as bits of it can get into the system.
I'm working Sat morning but only tidying up/cleaning. So if you want to bring it around for a second opinion, your welcome to.
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
mistergrumpy
|
| posted on 19/6/09 at 06:59 PM |
|
|
Just to close this off in case anyone searches for it. I think I've now sorted it. There was the very slightest weeping on one of the joints to
the bias valve that was tightened and seemed to have worked. That and fixing my bouncy front wheel guards and I thought I'd just nip out to try
them and fill up. It just bounced down and then stopped the second it was back in the garage 
|
|
|
.jpg)
.jpg)
