907
|
| posted on 23/3/15 at 04:22 PM |
|
|
Bleeding rear slave cylinders
Hi All
Below is a picture of a Sierra 13/16" rear drum brake slave cylinder.
I've tried to keep the pic as true to horizontal & vertical as I can so it represents how it's bolted to the back plate.
My question is; how are you supposed to bleed the air out when the brake pipe / bleed nipple holes are not at the top?
I'm actually fitting smaller 11/16" cylinders and struggling to get a pedal that isn't like a French cars suspension.
I look forward to your comments,
Paul G
 
Description
|
|
|
|
|
britishtrident
|
| posted on 23/3/15 at 04:41 PM |
|
|
Perfectly normal wheel cylinder design ( a slave cylinder in automotive is a clutch part) the brake self-adjuster have to be manually so the brake
shoes just skim the drum, top up the reservoir open the bleed nipple the minimum amount to allow fluid flow, get assistant press pedal down and hold
it down, close the nipple, assistant can then let pedal up slowly.
If pedal still soft repeat a couple of times.
If that dosen' work it is more than likely you have either a tiny fluid leak at a pipe union or a seized calliper.
[Edited on 23/3/15 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
adithorp
|
| posted on 23/3/15 at 04:50 PM |
|
|
Doesn't really make sence does it. However thats the way ford cylinders have been for years and it works. One thing you do need to do (to reduce
the volume in the cylinder) is bleed the brakes with the adjusters fully released. Another thing that helps sometimes to get the max amount of air
out, is once you've finished the normal bleed procedure, open the bleed nipple and push both pistons fully in (use screw drivers) before locking
up the nippel.
You can use the same technique as a quick method to bleed the cylinder IF you're just changing the cylinder on an already filled system; remove
clamp from flexi, open nipple, let fluid run through, push pistons in, lock off, let pistons float back out and repeat a couple of times.
When you refit that piston be sure to wet the seals with brake fluid first.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
907
|
| posted on 23/3/15 at 06:52 PM |
|
|
quote:
Originally posted by adithorp
Doesn't really make sence does it. However thats the way ford cylinders have been for years and it works. One thing you do need to do (to reduce
the volume in the cylinder) is bleed the brakes with the adjusters fully released. Another thing that helps sometimes to get the max amount of air
out, is once you've finished the normal bleed procedure, open the bleed nipple and push both pistons fully in (use screw drivers) before locking
up the nippel.
You can use the same technique as a quick method to bleed the cylinder IF you're just changing the cylinder on an already filled system; remove
clamp from flexi, open nipple, let fluid run through, push pistons in, lock off, let pistons float back out and repeat a couple of times.
When you refit that piston be sure to wet the seals with brake fluid first.
Reducing the volume makes sense.
The shoes are about half worn so the drums slide off easily without letting off the adjuster, so I didn't.
Next time I will. Don't like to clamp the flexible's as they're Goodridge stainless braided.
The one in the pic isn't going back on as the plan is to use the smaller ones to reduce rear braking.
I now know how those army blokes feel stripping down a machine gun in the dark.
I've got just enough fluid for one more strip down then I'm thinking of buying it by the gallon. 
Cheers
Paul G
|
|
|
adithorp
|
| posted on 23/3/15 at 08:43 PM |
|
|
Alternative to clamps when you've got braided hoses is to fill the res' to the brim then put a plastic bag over it and hold either by
screwing the lid on (if it doesn't have a float attached) or an elastic band tightly around it. You'll get a little drip from the pipe
then it'll air-lock and stop.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
rusty nuts
|
| posted on 23/3/15 at 09:28 PM |
|
|
Paul try pulling on the handbrake then give the pedal a few pumps, release the pedal for a couple of seconds then push the pedal down and hold it. If
the brake pedal is firmer then you need to manually adjust the auto adjusted . Release the handbrake and slacken the cable adjuster off , remove the
brake drums and look for the auto adjuster ratchet and pawl , put a large screw driver between the wheel cylinder piston and brake shoe gently lever
the shoe away from the piston, the ratchet should click up to adjust , go one click at a time then refit the drum and check for free rotation , repeat
until the drum just binds then release the ratchet one click , repeat for the other side, hopefully you will get a decent pedal then readjust the
handbrake. It may be the pivot points are seized , if they are free them off before adjusting. Sounds long winded but should only take a few seconds.
If your still not happy I have a hand pumped pressure bleeder you can borrow, it's even full of fresh fluid
|
|
|
907
|
| posted on 24/3/15 at 07:46 AM |
|
|
I will try to describe the situation.
The cars up on trestles, so 4 wheels off the floor with suspension drooping.
All wheels turn easily with slight rubbing noises from pads on discs & shoes on drums.
Handbrake adjusted to 4 clicks.
With slight pressure on the pedal it becomes impossible (for the wife) to turn any of the wheels by hand.
Pushing harder on the pedal, as you would braking for a corner, the pedal feels solid (ish) but with max pressure
on the pedal as you would in an emergency stop the pedal gently sinks another 10 to 15mm, but still it's only half way down.
This makes me think that I'm compressing the air bubble that I think remains in the "wheel cylinders".
I have tried two types of bleed systems. A Sealey vacuum type and an Gunsons Eezibleed pressure type.
I haven't tried the "assistant method" as I haven't got a "trained" assistant.
Cheers
Paul G
|
|
|
britishtrident
|
| posted on 24/3/15 at 09:16 AM |
|
|
(1) (a) Seized front caliper piston or (b) if floating calipers a sticking caliper guide pin.
or
(2) (a) Fluid leak either at junction or (b) an internal to master cylinder leak back through the recuperating port to the reservoir.
(1) (a) For Cortina/Escort calipers: Take the pads in turn out by one, stick a screw driver or lever in the gap where the pad came out, then push the
pedal once -- the piston should move. Push the piston back place the pad back in and repeat the procedure.
1(b) For Sierra calipers check the floating section of the caliper can move on the caliper guide pins and check the steady spring (aka anti-rattle
clip) is fitted.
(2) (a) Leaks can be tiny and not actually show much visible fluid leakage, go round each junction with a dry wipe and a torch while an assistant
puts pressure on the system.
(b) First test for a master cylinder is to slowly put gentle pressure on the brake pedal if the pedal slowly sinks then the master cylinder valves
are history. The other test is to remove all the connection to the master cylinder and give a very quick bleed then repeat the previous test. You
can minimize fluid loss when disconnecting the pipes with the polly bag/cling film trick or just getting an assistant to hold the pedal down.
[Edited on 24/3/15 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
907
|
| posted on 24/3/15 at 11:13 AM |
|
|
I'm puzzled BT.
Why the constant reference to seized calliper piston?
You know that my callipers have been stripped down and re-sealed because you replied TWICE on
my thread "m16 calliper piston removal tool".
I also speak of doing this job alone, (see last line of my last post) so replies with "just get an assistant to hold the pedal down"
I'm afraid isn't any help.
I always try to read a thread, then read it again before I chance an answer.
Please please please, do the same.
Paul G
|
|
|
.jpg)
