bad brakes

[sharki786]

hi all. im having right mare with the brakes. i changed pads and discs and changed the rear calipers to the mk4 ones. now when i changed everything i got air into the system. i bled all 4 brakes, that made f all difference so we then bled the abs unit which made a tiny bit of difference. now i still have poor brakes. my unc who is a mechanic said change the master cylinder as the seals inside the cylinder are fooked. the problem is that when i use my brakes they start to fade and braking becomes sh1te. my foot is nearly to the bottom and if i push the brake pedal more its right to the bottom. i didnt have this problem before i changed the brake pads and discs.
could anyone shed any light on this?
its the agg engine 2.0 gti
thanks

[hobbiniho]

when you say you got air in do you mean the reservoir went dry?? if so have you bled the master cylinder?? i take it that when you were bleeding the rear brakes you had the brake compensator held open?

[sharki786]

think the master cylinder went dry as i left it open but im not positive.
dont think there is a compensator on the mk3 gti. the car is a 1996 anniversary.
how do i bleed the master cylinder?
also i have noticed that i topped the bottle up a few months ago and have just noticed that its on low. think there is a leak but aint noticed one anywere

[Len]

You still have a lot of air in the system

[tweed]

Get a mate to help you bleed them. Start with driver rear and bleed it 10+ times (keep topping up with fluid) then same with passenger rear. Then driver front. And passenger front last. Put about 1/2 litre through it.

Always check and top up fluid.

[VW BUSH]

Bleed the brakes again after activating the abs either with vc (best) or by braking on a loose surface a few times.
Seeing as you had no issues before I would say it would be really unlucky to have a duff master, be sure you have air free brakes before  you change the master cylinder they are not cheap and quite fiddly.
I always use a different colour fluid to bleed through when I am having brake bleeding issues, a pressure bleeder helps a lot. I also stay away from the abs if I can help it.

[VW BUSH]

Get a mate to help you bleed them. Start with driver rear and bleed it 10+ times (keep topping up with fluid) then same with passenger rear. Then driver front. And passenger front last. Put about 1/2 litre through it.

Always check and top up fluid.

Mate or mum with a cuppa and her slippers on really helps

[sharki786]

My mates dad said same. I have air in the system. Is there a way of testing the master cylijder?
Im going to get the lads to use the ezibleed thing

[VW BUSH]

My mates dad said same. I have air in the system. Is there a way of testing the master cylijder?
Im going to get the lads to use the ezibleed thing

Yes you can pressure test the flow side with a gauge to see if it holds pressure, will show up a straight fault at least.
Had any fluid on the top of the pedal linkage?
I reckon you just let a load of air in at the callipers and abs unit

[sharki786]

I have lost some fluid but i aint seen a leak anywere. Well ezibleed will pressurise the system wont it?