hydraulic handbrake help

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kds19
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hydraulic handbrake help

Post by kds19 » 23 May 2010 01:46 am

right i fitted a hydraulic handbrake to my 360 but cant get it bled its as it sucks in air while im bleeding it.
its hooked upright cos i have had it working it just wouldnt stay bled
i have fitted new rear wheel cylinders, a new rear flexi hose, new copper pipes from front to rear
the brake master cylinder must be fine as when i blank off the rear brakes the pedal is solid and stays the way so its definately
something in the new rear system
and old man at my work told me the way i have hooked it up couldnt possible ever work without a compensation valve which is shite as i have had it working
it just wont stay bled the wierd thing is that its not leaking any fluid from anywhere.
i even replaced the handbrake master cylinder thinking it was maybe a dud one but it made no difference
is it possible for the pipe ends to let in air but not let fluid out?
someone help me
cheers
kev
85 360 GLT drift beast
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CBA
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Re: hydraulic handbrake help

Post by CBA » 23 May 2010 03:49 am

you need a one way valve (ish) between the cars master cylinder and the handbrake master cylinder, otherwise the fluid will go straight into the front master cylinder when you use the handbrake, the first use of the handle will probably work (a bit*) , but pull it a few times and it wont, if you "pump up" the front brakes then maybe it will work again proving this hypothesis.

Without that valve the handbrake will work as a master cylinder to rear brakes but force fluid into the front master cylinder, turning it into a reverse slave cylinder... and from there it gets complicated.





If that sounds wrong then can you give me a diagram of what you've setup?

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volvodspec
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Re: hydraulic handbrake help

Post by volvodspec » 23 May 2010 08:40 am

no you don't just need a one way valve; that's just dangerous.. as soon as you brake with the pedal the pressure stucks behind the valve eventually locking the rear wheels permanently
there is a special control valve available along with the hydraulic handbrake, most of the time you get it with the handbrake in the box. part of this is a restrictor and a one way valve. the way this is setup in the hydraulic scheme makes permanent pressure buildup behind the hydraulic handbrake with applying the pedal impossible

you definatly need this it; the mastercylinder can't cope with reverse pressure buildup.

about the bleeding, if you renew hoses/cylinders/brakelines etc, pumping the pedal takes ages. instead, apply overpressure to the resevoir (max 1,5 bar) and simply open the drains to bleed it.

there are special tools for it; these pump brake fluid at this correct pressure into the resevoir; very handy!!
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kds19
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Re: hydraulic handbrake help

Post by kds19 » 23 May 2010 11:47 am

does anyone have a link or something to one of these valve things that i need?
85 360 GLT drift beast
clutch kicks ahoy!!!!
"volvosneverdie wrote: Fred Dibnah was running after me on the scuttling legs of a crab. in a tophat."

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Frits
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Re: hydraulic handbrake help

Post by Frits » 23 May 2010 12:34 pm

the handbrake does already has that "valve". The handbrake cilinder simply "locks" the feedpipe from the front and build up pressure to the rear.

But I was wondering, when you toke your car for a ride in the morning, didn't you had any pressure at all? And the evening before it was rock hard?

I had many problems with my master brake cilinder, all the second hand stuff is rubbish shit. A new one solved all problems. But I don't see why you have no pressure in the morning, while the car wasn't used meanwhile and being rock hard...

You don't lose any breakfluid do you? And the level in the master brake reservoir stays ok and exactly the same level?

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kds19
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Re: hydraulic handbrake help

Post by kds19 » 24 May 2010 05:36 pm

yeah definately no fluid leaks and level stays the same
85 360 GLT drift beast
clutch kicks ahoy!!!!
"volvosneverdie wrote: Fred Dibnah was running after me on the scuttling legs of a crab. in a tophat."

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volvodspec
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Re: hydraulic handbrake help

Post by volvodspec » 24 May 2010 05:48 pm

hmm that is starting to look like master cylinder, or the brake balance unit..

what if you get the car on blocks all round, apply footbrake and check if the wheels lock?
repeated with the hydraulic handbrake

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Frits
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Re: hydraulic handbrake help

Post by Frits » 24 May 2010 07:08 pm

But I was wondering, when you toke your car for a ride in the morning, didn't you had any pressure at all? And the evening before it was rock hard?
And that? Plus, does it gets any pressure when you pump the pedal?

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Ronnie
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Re: hydraulic handbrake help

Post by Ronnie » 24 May 2010 07:26 pm

The master cylinder is only 5 years old on that car, I doubt that's where the problem lies
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kds19
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Re: hydraulic handbrake help

Post by kds19 » 25 May 2010 06:22 pm

i cant really remember now but i think when i lost all brakes was when we found the leaky hose :oops: :oops:
but it still doesnt explain why it is so hard to get all the air out and even get brakes
managed to get it bled a bit last night and its seems to be staying the same spongyness
so hopefully its just a case of getting it bled properly now

also read through my haynes manual and found out that it has a compensation valve would this effect it much??
85 360 GLT drift beast
clutch kicks ahoy!!!!
"volvosneverdie wrote: Fred Dibnah was running after me on the scuttling legs of a crab. in a tophat."

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