Hasse
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| posted on 27/6/05 at 10:02 AM |
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rear brake drives me crazy
Hello,
I hope some one can give me some advice, as my rear brakes overheats very easily.
8" drums on standrad Escort mk2 axle. All parts new: drums , 19.05mm cylinders, and brake shoes in correct position.
They brake ok, but it seems as the self adjusting mechanism adjust "to much" as the the rear brakes tends to stay on a little after
braking. Even if its not at all much, possible to push the car manually, it seems as this is enough to heat the drums A LOT. My new drums have already
taken on a blue colour internally.
The problem occour on both sides, and I have tried to brake a bit softly in order to "bed them in".
Anyone recognising this problem?
All proposals are most welcome since I do not seems to be able to solve this with a lot of time spent.
/Hasse
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nick205
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| posted on 27/6/05 at 10:39 AM |
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Is the handbrake cable adjusted properly and moving freely?
Nick
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wilkingj
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| posted on 27/6/05 at 10:43 AM |
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Have you got the leading and trailing edges of the shoes the correct way round?.
And as nick says, is it adjusted up correctly.
You can also check that the brake pedal is releasing fully (hydraulic problem?)
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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Hasse
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| posted on 27/6/05 at 02:50 PM |
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Sorry to say, but...yes, yes,
Leading and trailing shoes are mounted according to manual. Hand brake is moving freely and the cylinders are easy to "compress back" with
the pedal in "rest position".
As I have understod, only the foot brake action, not hand brake action, makes the self adjusting mechanism to "step forward".
I hope someone have seen or heard about the problem, or is it only me who has got this wrong?
/Hasse
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britishtrident
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| posted on 27/6/05 at 03:04 PM |
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Assuming you havent go the handbrake cable to tight, the most likely cause is your master cylinder push rod isn't comming back fully --do you
have a return spring on the pedal, and is the mushroom at the cylinder end of the pushrod allowing the piston in the cylinder to come back fully.
[Edited on 27/6/05 by britishtrident]
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tks
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| posted on 27/6/05 at 06:40 PM |
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drum brakes
isn't the problem laying the area where the shoes adjust itselfs??
the hydro action dont put the shoes back do they?
if i remember its an springs that does this..??
shoot an good pic of the druk plate with all tis components so we can see good how the adjust mechanism works..
for me its an problem of there or your drums moves sow the things adjusts and then suddenly it moves back and it is adjusted to tight?? bearings??
is your drum worn patern equal??
because else in an 'hole' bad zone it could adjust and then at the other zone it will block..
Tks
The above comments are always meant to be from the above persons perspective.
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britishtrident
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| posted on 27/6/05 at 07:32 PM |
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The self adjuster on Ford Escort Girling brakes is pretty well fool proof it can't over adjust because the clearance is pre-determined by the
design of the ratchet mechanism. So if everything is free inside the drum that only leaves the handbrake or the pedal/mastercylinder.
The handbrake is easy to check just give the cable a load of slack, the pedal/master cylinder is trickier to tie down a diagnosis on.
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davidwag
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| posted on 27/6/05 at 08:10 PM |
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Hi,
If you jack the car up is the brake dragging?
If it is you could try opening the bleed nipple whilst rotating the wheel by hand.
If the wheel goes free when you do this you'll know its residual pressure in the brake lines.
Also remember that the hand brake is designed to operate at about seven clicks otherwise the self-adjustment doesn't work correctly.
David
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Hasse
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| posted on 28/6/05 at 06:26 AM |
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Thanks for your feed back guy´s!
I´ve thought about your comments, but have´nt had the time to check yet.
There might be something about the main cylinder as you have meantioned?
Could it be that the engine heat has an influence?
The brakes are ok when I go away for a short trip, but after some time, I can feel a slight "unwanted" braking. Maybe the pushrod is a bit
to tightly adjusted to the main cylinder, wich is ok at cold, but some clearance is "eaten away" when heat is building up under the
bonnet??
I will check tonight.
/Hasse
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britishtrident
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| posted on 28/6/05 at 11:08 AM |
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If the master cylinder piston isn't returning fully you get a hydraulic lock, as the brake warms up the fluid heats up and expands forcing the
shoes/pads into contact with the disc/drum generating yet more heat.
It is quite often found on kit cars and racers with special or modified pedal boxes but it is also common on road cars with servos where the servo has
been changed if the pushrod adjuster on the master cylinder side of the servo hasn't enough lost motion (it needs about 2 to 3 mm
clearance).
[Edited on 28/6/05 by britishtrident]
[Edited on 28/6/05 by britishtrident]
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Hasse
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| posted on 30/6/05 at 08:12 AM |
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No, I have checked again, no hydraulic problem. The push rod clearance at the master cylinder is ok.
The self adjusting mechanism do "step up" during braking/driving, but the cylinders are easy to push back, so there is probably no
hydrualic locking.
I´m currently thinking if I have a to big brake pedal ratio making me "overstrong" at braking and by this deforming the brake shoes/drums
during braking.
This could maybe explain the unwanted activation of the self adjusting mechanism? My present brake pedal ration is about 6:1, without servo, and the
brake pedal force during hard braking as fairly low.
It is easy to control the braking from soft to hard, but the pedal feeling is a bit "spongy".
Changing the ratio is not so easy, but maybe nessesary?
What do you think?
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britishtrident
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| posted on 30/6/05 at 12:05 PM |
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Durring braking you will only ever apply equal or less force than it takes to lock the rear wheels this should be less than the original road car.
Brake drums do distort -- I had problems with this on Hillman Imp racers which also had Girling 8" brakes but the most likely symptom is just
inefficient rear brakes or a spongey pedal.
I would check the the handbrake cable isn't geting pulled by suspension movement, also if you have the orignal Escort handbrake cable with the
rubber flap hinge this can cause problems.
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