Hasse
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| posted on 18/5/05 at 06:19 AM |
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Brake hydraulics principle?
Hi,
Been out test driving my car before SVA and meassuered the brake performance since we have a demand of at least 0.8G retardation in Sweden.
Managed better than 0.9 without problem, but have almost no baking at rear right drum. (Almost ambient temperature while left drum and front discs
were hot).
Was my thinking stupid when I connected the rear brake pipe directly to first the left brake cylinder and from that one over to the right cylinder?
I thought that the brake fluid pressure would be the same in the system and in that way produce the same brake action in both rear drums, even though
they are connected in "series".
How does it work?
It´s easy enogh to change into a T-split, but will it solve my problems?
/Hasse
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Hellfire
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| posted on 18/5/05 at 06:38 AM |
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As you have connected them virtually in series, it would suggest the right drum is building pressure whilst the left is not. Given that the forces to
move the piston's may not be exactly equal (say left is a tighter fit) then left will 'drag' on the drum before right even moves.
There may also be a problem with the mechanism or flow on the right.
Personally I would connect in parallel using a T and go from there, purely because it is a proven method. At least it eliminates the problem you are
experiencing and then points to another area.
I could be wrong - and often am! 
[Edited on 18-5-05 by Hellfire]
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silex
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| posted on 18/5/05 at 07:01 AM |
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You already have ' T ' d it in. there is no difference between having the joint at one side or central between the brakes (other than very
very small losses in the pipe work), unless you could run parallel from seperate ports on the master cylinder.
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I think hellfire is right in that you are suffering mechanically on the brake itself - sticking or similar.
[Edited on 18/5/05 by silex]
Hey how come you can't draw in asci - I cant get anything to line up. The second set of double vertical lines should be in the centre of the
second brake line connection !!!!
[Edited on 18/5/05 by silex]
Murphy's 2 laws
1. If it can go wrong it will
2. In case of emergency - refer to rule 1.
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britishtrident
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| posted on 18/5/05 at 08:06 AM |
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What rear axle are you using if it is an Escort with the Escort cable there is a known problem of the handbrake mechanism interfering with the
operation of the foot brake, try slackening back the hand brake cable, remove the drum and check the operation of the wheel cylinder piston(s).
On early MK1 Escort axles also check the wheel cylinder is sliding freely in the back plate, replace the drum and adjust the brake.
On Mk2 axles check the wheel cylinder pistons and the operation of the self adjuster mechanism -- run up self-adjuster so it just alows enough
clearance to refit the drum.
When re-adjusting the handbrake cable allow enough slack for the self-adjusters and wheel cylinders to work -- too much tension and the
self-adjuster and wheel cylinder will be "choked" by the handbrake mechanism.
In late 1970s/1980s the UK it was quite a common modification to replace the cable on Escorts with one designed for a Morris Marina/Ital is this
eliminated the rubber flap hinge which caused a lot of problems with asymetric braking as the rubber hinge age hardened.
[Edited on 18/5/05 by britishtrident]
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Peteff
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| posted on 18/5/05 at 09:01 AM |
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The one that's not working is probably seized. Jack it up and check if it spins when someone applies the footbrake, then apply the handbrake and
see if that works. There's nothing wrong with the way they are connected as long as the bleed nipple is in the top hole of the brake cylinder.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Hasse
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| posted on 18/5/05 at 10:22 AM |
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Thanks for your replays,
I´ll check the parts once again, especially the hand brake bits, allthough all parts are new or reconditioned.
With your answers I will stay with the present build up, using one of the cylinders as "T-split" a while longer.
/Hasse
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NS Dev
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| posted on 18/5/05 at 01:02 PM |
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as above, I would strongly doubt there is a problem with the piping, almost certainly a mechanical problem.
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