My seals are failing under light pressure.  I have bought a new master
cylinder but I have never changed one before only changed brakes and
bled them.  When filling the new cylinder with fluid does the pedal
have to be pumped to distribute the fluid or can I just use the gravity
method of bleeding.  I have used a tube with a none return valve in the
past but somebody recommended the gravity method.  I do not want to
fork out for a pressure bleeding kit.

"gJF"  wrote in message 
news:1124705597.627951.106990@g14g2000cwa.googlegroups.com...

> My seals are failing under light pressure.  I have bought a new master
> cylinder but I have never changed one before only changed brakes and
> bled them.  When filling the new cylinder with fluid does the pedal
> have to be pumped to distribute the fluid or can I just use the gravity
> method of bleeding.  I have used a tube with a none return valve in the
> past but somebody recommended the gravity method.  I do not want to
> fork out for a pressure bleeding kit.
>

Last time I did an astra m/cyl I gravity bled it but it wasn't very good so 
I pump bled it and the pedal came back spot on.

OK, Thanks for the advice.  Just waiting for some fine weather.

I have managed to borrow a pressure bleeding kit.  What pressure should
I use in the car tyre and would I still need to pump the pedal when
fitting a new Master cylinder.  The instructions have been lost.

I know I have to bleed out all the air bubbles but can anyone tell me
how to estimate how  much fluid it takes in the master cylinder to go
through the brake pipe to reach the back brakes.  Would it be like half
the reservoir capacity or more.

On Tue, 23 Aug 2005 10:35:57 +0100, gJF  wrote:


> I know I have to bleed out all the air bubbles but can anyone tell me
> how to estimate how  much fluid it takes in the master cylinder to go
> through the brake pipe to reach the back brakes.  Would it be like half
> the reservoir capacity or more.
>



By the time you've bled them, more.

On Tue, 23 Aug 2005 17:55:52 +0100, gJF  wrote:


> I have managed to borrow a pressure bleeding kit.  What pressure should
> I use in the car tyre and would I still need to pump the pedal when
> fitting a new Master cylinder.  The instructions have been lost.
>



Depends on the car, most work well with 10-12psi, you don't necessarily  
need to pump the pedal & there's some argument that f it's an old &  
corroded master cylinder you don't want to.

On Tue, 23 Aug 2005 17:58:54 +0100, Duncanwood   
wrote:


> On Tue, 23 Aug 2005 17:55:52 +0100, gJF  wrote:
>
>> I have managed to borrow a pressure bleeding kit.  What pressure should
>> I use in the car tyre and would I still need to pump the pedal when
>> fitting a new Master cylinder.  The instructions have been lost.
>>
>
>
> Depends on the car, most work well with 10-12psi, you don't necessarily  
> need to pump the pedal & there's some argument that f it's an old &  
> corroded master cylinder you don't want to.




Of course givem the word "new" you can ignore that bit.