slowbuild
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 posted on 20/2/03 at 09:11 PM |
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Brakes driving me mad
Hi, I am using the standard sierra mcyl (less servo) and cannot get the rear brakes to provide any sort of stopping force! Could they just need
bedding in?I dont think its bleeding as the pedal pumps up solid after 2 strokes.The Cortina fronts are as taken from the scrappie (do they need
reconditioning?)
I believe that the mcyl less servo can be a bit tricky to set up - is their one designed for use without a servo, available on another car that would
be a direct replacement?
Any help gratefully recieved!!!
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theconrodkid
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| posted on 20/2/03 at 11:46 PM |
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have you got a balance valve?are the flex,s ok and not squashed,is the master cylinder any good,are you getting any fluid to the rears????
who cares who wins
pass the pork pies
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slowbuild
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| posted on 21/2/03 at 09:06 AM |
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Cheers,
The mcyl is new, and the flexis are from lolocost. I have fitted a tilton lever reducing valve which is set at no reduction!
When I press max pressure on the pedal you can still grip the wheel and turn it (although it does take a bit of effort)!
I take it a lot of builders have used this setup succesfully.(couldn't afford a balance bar set up)
The rear pads are new, as are the self adjusters; which you can hear click up on the initial application of the pedal after fitting.
Still driving me mad! - Just sheared an exhaust stud aswell!- can these be easily drilled out?
Thanks for your reply
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slowbuild
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| posted on 21/2/03 at 09:11 AM |
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There is plenty of fluid coming out of the rear bleeds- have put nearly half a gallon through it! One thing however- the rear brakes are on upside
down i.e. cycls at the bottom!but as they are horizontal in terms of feed and bleed I didn't think this should matter. Could be proven wrong of
course!!!
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johnston
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| posted on 21/2/03 at 09:18 AM |
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make sure your shoes are adjusted up at the self adjusters not the h/brake cable
quote:
pedal pumps up solid after 2 stroke
should it not be solid after 1
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Barker
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| posted on 21/2/03 at 12:07 PM |
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there is a brake bias cylinder which goes in line to push 25% more barking to rear I think you need to fit this to pass SVA. Its a small device about
the size of two golf balls!!!
have you got enough leaverage from the pedal onto the push rod????
pete
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Dick Axtell
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| posted on 21/2/03 at 04:00 PM |
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Slowbuild -
The Sierra mcyl was designed for use with a booster, which provides the backstop for the pistons. By removing the booster you eliminate the
backstop.
The booster output rod (which abuts the primary piston) is factory-set to +/- 0.15mm. You will need to replicate this condition, with any linkage
between brake pedal and mcyl piston. You will also need to ensure that the mcyl pistons return sufficiently to release the brakes.
After reaching your hard pedal condition, do your brakes release immediately with pedal release?
P.S. You could try using Mk.1 Fiesta non-servo mcyl, but check the displacements relative to your brakes.
[Edited on 21/2/03 by Dick Axtell]
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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Dick Axtell
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| posted on 21/2/03 at 04:06 PM |
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quote:
Originally posted by Barker
there is a brake bias cylinder which goes in line to push 25% more barking to rear I think you need to fit this to pass SVA.
Pardon? What's this about?
Normal vehicle brake engineering practice was to fit a proportioning valve, in the rear brake line. This reduces the pressure supplied to the rears,
compared to that supplied to the fronts. Beefing up rear brake pressure, relative to front pressure is a recipe for disaster!!
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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theconrodkid
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| posted on 21/2/03 at 08:14 PM |
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sounds like either the pressure reducing valve is doing too much or the master piston is coming to the end of its travel before it should,you got them
plumbed in the right way round?
who cares who wins
pass the pork pies
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slowbuild
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| posted on 21/2/03 at 10:30 PM |
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The brakes do seem to release as soon as the pedal is released.There is plenty of travel in the mcyl as when released you can manually rotate the
pushrod so there is no residual pressure on the mycl when the brake is released.Maybe if I remove the rear drums and allow the self adjusters to click
up a couple of times this will hold the shoes a little closer to the drums resulting in less travel required to apply pressure????? - Could give it a
try -If not may have to resort to the fiesta mycl but is that not a diagonal split system? can it be altered to suit??
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bob
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| posted on 21/2/03 at 10:51 PM |
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The self adjusters could be the problem,i had this problem on a car once where the ratchet system was failing .
I was driving around with the handbrake on a couple of notches to give better braking.
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slowbuild
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| posted on 21/2/03 at 11:14 PM |
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I see what you mean but the adjusters are brand new genuine ford! £25 aswell!!!
They do seem to work as you can hear them clicking up on initial application after overhaul - having said that the wheels rotate very freely as if
they are too much released when there is no pressure on the brake pedal! Can you see now why its driving me so mad!!!!
The bias valve is correctly fitted!
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jollygreengiant
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| posted on 21/2/03 at 11:21 PM |
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quote:
Originally posted by slowbuild
One thing however- the rear brakes are on upside down i.e. cycls at the bottom!but as they are horizontal in terms of feed and bleed I didn't think
this should matter. Could be proven wrong of course!!!
Hmmmm. Bleed screws into slave cylinders are designed and constructed to make sure that when the cylinder is fitted correctly and the bleed screw is
opened then fliud and air will pass out from the very top so that no air can possibly be left in the cylinder. You however are expecting fluid and air
to react in the same manner as rover did with their 100's, 200's and 400's. that is air to flow down hill in water and water to flow up hill
against gravity. This does not work which is why it is a pain in the arse to bleed out the cooling systems on the rover models previously mentioned.
and you will probably find that no matter how hard you try you will always have residual air left in your slave cylinders until you fit the cylinders
in their original design positions. Also you will will find that you have reversed the role & the operational function of the shoes by fitting the
cylinders at the bottom of the back plate.
Enjoy.
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Rorty
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| posted on 22/2/03 at 02:29 AM |
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I'll second what JGG said. Also (though I don't believe this is your problem), don't expect too much from a totally new brake system until the
brakes bed in a bit.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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theconrodkid
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| posted on 22/2/03 at 03:15 PM |
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you could try a pressure bleeder,that will blast out any air in the system
who cares who wins
pass the pork pies
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johnston
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| posted on 22/2/03 at 07:16 PM |
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have you definatly got all the springs on right??
adjust up your shoes till their just rubbin the drums i find best way is 2 big screwdriver to lever them apart
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Barker
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| posted on 25/2/03 at 08:43 AM |
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have just read my note - the compensator gives bias to the front NOT the rear - sorry guys
pete
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