Testing brake master cylinder

[Serial 0]

Hi all,

 

After having spent most of this weekend bleeding about 2 litres of fluid through the brake system, and still not getting anything like a firm pedal, I've come to the conclusion that it must be the master cylinder that's at fault. The brake pedal goes all the way to the bottom with the engine on - I can feel it coming to a stop at the limit of it's travel.

 

So, I've thought of a method of testing the master cylinder to confirm that it is definitely faulty before spending >£250 on a new one (it's the rare ABS one).

 

If I were to make up a short length of hard line (say 6" long) and connect it to the master cylinder output port, then bleed fluid so it comes out of the end of the line, and then clamp the line closed at the end, this should isolate the master cylinder from the rest of the braking system. If it's working properly, then the pedal should be completely solid as no fluid could be pumped along the closed line. If the seals are dodgy then the pedal would still be soft and would slowly sink down under pressure as the fluid seeped past the seals.

 

Anybody see any problems with this method? I might try it tomorrow night and report back...

[Supercharged 2]

Have you bled the nipple on the MC? - this is key to getting a good pedal

[Serial 0]

Yes - bled everything in order including the two on top of the ABS pump and the master cylinder.

[G60 CS 0]

Im having problems with the same thing, except of a G60

having changed all my brake pipes and fitted mk 4 rear callipers I now can get any fluid to the off side rear calliper and the fluid that comes out the front looks full of air. I dont know of anywhere I can get a replacement MC or a repair kit

[stereoflaver 0]

Get one of these

 

http://www.gunson.co.uk/item.aspx?cat=674&item=1818

 

I couldnt get a pedel when doing my clutch master cylinder for three days, got this n had a pedel in less than three minutes.

 

I got mine from machine mart.