Kitlooney1000
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| posted on 13/4/04 at 08:09 PM |
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Brake problems on mates car still !!!!
My mate 7 has had a problem with the breaks from before he bought it. On a journey the front brakes would seize on. we swoppped the pipes on the Mk3
capri master to see if the master was at fault, but it was still the fronts that were seizing. replaced the front flexi's and the rear one
anyway. replaced the front calipers with recon ones, the rear cylinders with new ones, the rear drums, the front pads, the pedals were stripped out
and a new set fabricated to fit the car. there is enough play on the pedal to allow the piston on the master to come fully out. the pipe work in the
engine bay runs either side of the engine for the front brakes, as in it comes out of the master, t-piece to split the pipe, then one pipe for each
side around the engine to the new flexi's. the only thing we havent done is replace the brake lines, although they have been flushed several
times.
One thought is the heat from the 4-1 exhaust manifold on the 1700 xflow is expanding the brake fluid, as it is fine if you release the pressure
through the calipers bleed nipples.
Any thoughts anyone, before the car has a sledge hammer taken to it, or turned into a dutton, either way is easy 
[Edited on 13/4/04 by Kitlooney1000]
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Andy S
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| posted on 13/4/04 at 08:28 PM |
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Interesting problem - does the brake pedal / push rod assembly allow the master cylinder to return to the fully open position i.e. is there any
play?
If there is then it sounds like a new M/C or a rebuild is needed.
Ooops just red the thread fully - and you say it does return - Makes no sense.
Whats the layout - is the master higher or lower than the calipers?
Andrew
[Edited on 13/4/04 by Andy S]
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Mark Allanson
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| posted on 13/4/04 at 08:28 PM |
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Sounds like rear adjusters again.
You press on the brakes, the rear shoes extend, the adjusters should then hold them just off the drum, if they are worn, the springs slowly return,
squeeze the rear slaves and push the fluid back into the system. The only place for it to go is in the front calipers, and binding the front brakes
Harking back to my Fiat days (everyone yawns!!), the 60's-80's FWD fiats had a clutch type adjuster with single leading shoes. the rear
shoe would not adjust oner time as the shoes wore, and the front calipers would start binding. the cure was simple, drive the car in reverse at 20mph
and slam on the brakes, repeat until you are nearly sick and the problem was sorted. If the owner was told to do one emergency reverse stop every
week, the problem never reoccured. Italian engineering and Yorkshire solutions!!
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Kitlooney1000
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| posted on 13/4/04 at 08:31 PM |
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Good idea Mark.
The car has been tested with the rear brakes disconnected from the master cylinder with the same effect, still binding the fronts
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Andy S
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| posted on 13/4/04 at 08:39 PM |
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The way the Capri M/C works should prevent any pressure from the rear going to the front as the circuits are separate - In effect its two separated
cylinders.
Any pressure should be released back into the resevoir as a valve is opened when the piston fully returns. - I would replace the M/C - does the fluid
easiliy return into resevoir when the pistons are pushed back into the calipers?
Andrew
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Mark Allanson
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| posted on 13/4/04 at 08:42 PM |
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Whe you disconnected the rears brake pipes, did you replace the unions with bleed nipples and bleed out the master cylinder? If not, trapped air would
give the same result as worn rear adjusters!!
I just love brake problems, they really make you think!!
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Kitlooney1000
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| posted on 13/4/04 at 08:47 PM |
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Andy, havent tried to push the pistons back in, will try that next. Will also try to shield the brake pipe above the exhaust to see if that helps.
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Mark Allanson
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| posted on 13/4/04 at 08:56 PM |
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I am not sure about tha capri MC, but most separated MC's have a floating piston between the rear and front chambers so pressure from the rear
will push the floating piston against the front chamber increasing the pressure to the fronts. The pressure will also push the pedal back. Have you
got a solid or rubber pedal stop (see where I'm going now!)
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Kitlooney1000
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| posted on 13/4/04 at 09:03 PM |
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there is still play in the pedal, the m/c piston is fully out, even disconnecting the pedal doesnt help. but to answer your question the pedal stop is
solid.
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Mark Allanson
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| posted on 13/4/04 at 09:18 PM |
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That has ruled out most things. There are only 2 reasons why the brakes bind - pressure build up or mechanical resistance (in the pistons). As you
have changed the front calipers, it has to be either rear adjusters, master cylinder or boiling fluid too close to the exhaust, air in the system that
will not bleed out normally - like you, I am starting to run out of ideas.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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NS Dev
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| posted on 14/4/04 at 06:41 AM |
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In my experience it is nearly always the pistons seizing that causes the brakes to stick on. Just worth checking that the re-con calipersare not
seized, I have had this once, funnily enough with cortina calipers, supposedly recon but must have been sat on a shelf for ages and one were seized
when I put it on!! Another new one cured the problem!!
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britishtrident
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| posted on 14/4/04 at 07:43 AM |
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Very easy to diagnose the master cylinder piston is not returning enough to vent fluid back to the master cylinder.
On cars with servo this is usually caused by someone twiddling with the adjuster on the pushrod stub that comes out the cylinder end of servo in an
misguided effort to reduce pedal travel.
With non-servoed brakes you should always use a master cylinder designed for non servo use with a circlip and pushrod retaining washer at the
end.
[Edited on 14/4/04 by britishtrident]
[Edited on 14/4/04 by britishtrident]
[Edited on 14/4/04 by britishtrident]
[Edited on 14/4/04 by britishtrident]
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Kitlooney1000
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| posted on 17/4/04 at 07:15 PM |
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Have now ruled out the overheating, moved the brake pipes so they ran in a cool area, the bottom of the engine bay. stripped down the master cylinder
and fitted new seals all roung even though its a new one any way, no good. enquired as to the price of a new cylinder and my mate is now ordering a
set of tandems from rallydesign. hopefully that will solve the problem
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britishtrident
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| posted on 18/4/04 at 06:07 AM |
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quote:
Originally posted by Kitlooney1000
Have now ruled out the overheating, moved the brake pipes so they ran in a cool area, the bottom of the engine bay. stripped down the master cylinder
and fitted new seals all roung even though its a new one any way, no good. enquired as to the price of a new cylinder and my mate is now ordering a
set of tandems from rallydesign. hopefully that will solve the problem
All he needs to do is make sure the mastercylinder pushrod come back far enough to allow the piston to return fully.
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Kitlooney1000
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| posted on 18/4/04 at 09:42 AM |
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have ruled that out already, the recuperating valve in the master is fine, opens and closes with the movement of the piston. the fluid even returns to
the reservoir when you push back the brake shoe. nothing else left to check now
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Baldrick
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| posted on 19/4/04 at 11:50 AM |
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This happened on mine. Problem was cured by fitting positive return spring on pedal. Just the friction of the pedal/pushrod etc. was enough to keep
the brakes hard on once applied.
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Kitlooney1000
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| posted on 19/4/04 at 03:22 PM |
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Thats the next plan.
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