Poor brakes, pedal to floor

[MarkGolf 6]

Very strange problem on my car..

With car off, the pedal goes pretty firm but not super, with it on, it goes soft, so soft i can near enough get the pedal on the floor..

When driving, the car really is hard to stop, there is no bite, i put the pedal near enough to the floor and the car slowly stops..

My braking system is as follows..

No ABS, Corrado VR6 or Golf 16v Servo, 23mm M/C, ATE Super Blue fluid, Brembo 4 pot front, mk4 Golf rear, Wilwood Bias valves, fully braided lines throughout system (No copper)

The 1 way valve is plumbed in

I've bled the system over and over using an ezblled, I've removed the mk4 calipers and had them so the nipples pointdirectly up and still no joy, just have a shitty soft pedal which feels crap!

Anyone have ANY ideas to what could be the issues?

cheers

[S/Cmk2 0]

does it feel soft all the time when turned on or just after getting hot?

[legvw 0]

Sounds very similar to a problem i had recently.

Are you bleeding the system with the bias valve fully open? If not it could restrict the bleeding process.

Can you bleed the master cylinder? If you can bleed that last, after the calipers.

Can you lock the fronts wheels when moving? If you can't i'd say its the fronts thats causing the problems.

If you can lock the fronts then its your rear brakes.

Double check all the joints, as 1 thats leaking my allow enough air into the system to cause the spongey pedal.

Are you still using the vw split system-diagonal (n/s/f joined to o/s/r, o/s/f joined to n/s/r), or are you split front and rear ciruit?

When i bleed my brakes (split front and rear) i bleed furthest from m/c first, and bled through atleast 1 full ezibleed bottle, then the same for the opposite rear. Then did the fronts, starting from the furthest, then the opposite.

[Scott 0]

buggered seal in the master cylinder? Happened to me on an SD1 years ago, the seal flipped out of the groove under heavy braking and the brakes went soft and shitty, the reason yours is hard when off is the servo assistance is not there with the engine not running,

if the piston seal in the master cyl is gone, there will be very little hydraulic pressure at teh calipers and no brakes to speak of.

[MarkGolf 6]

Hi

It feels soft ALLLL the time when driving, I had to take it on a 50 mile round trip yesterday and the whole time the pedal was soft. The only ime it firms up is when it is off!

I did suspect the M/C to be at fault but I fitted a brand new VW 22mm one I had laying around. The results of this were identical to what I had with the previous 23mm.. I could be unlucky and have a faulty one.. I did have 2 brand new faulty fuel pumps from VW.. lol

Paul, I am bleeding the sytem with the bias valves fully open. My M.C only has the 2 port for the brake lines, it's not a 4 way one..

I don't think I can lock the brakes at all tbh, definetly not at speed of 30 or less.. I am using the VW system as ou mention above. I have bled them in that manor too, start further to cloest with my EZbleed kit.

I' certain it's not a vacuum issue now as a few people have said if it was a vac leak, the pedal wouldbe firm, not super soft like is!

Perhaps I am unlucky and I do have a dodgy M/C.. I just can't think what else it could be and it really is giving me a headache!

None of the braided lines in/out/under the car appear to expand under pressure, calipers are working, no fluid leak, everything is tight.. I'm lost!

[legvw 0]

If you can send me a pic of your m/c i might be able to send you a working 1 to try if you like?

[Scott 0]

you certainly have no hydraulic pressure being developed (or very little) if the pedal is soft and brakes crap below 30, the hard pedal when engine is off is down to no more vac assistance, and your right, vac leak would be the opposite effect.

Does the car have abs?

if so you need vagcom to purge the abs pump, but if you dont, and theres no fluid leaks, I would have to suspect the master cyl for sure, too much vac would make the pedal softer but the brakes would be better, even lethal in fact from more power assistance, so I reckon the MC is goosed or fluid would be coming out of a leak somewhere, thats the only way to get a soft pedal and shit brakes, mc piston seal gone, or a leak. Or very long travel can be very very worn pads and air in the system but as youve bled it and presumably checked the pads, thats all that can be wrong.

With the engine running, does pumping the pedal improve the brakes and firm up the pedal pressure?

btw if you get or have vagcom, do NOT under ANY CIRCUMSTANCES test the ABS controller while moving, you will climb a tree - it triggers each caliper to brake hard one corner at a time, then whacks all 4 on hard, then all off - you wont know its coming but a friend went with another guy in the car using the laptop, and he ran the abs diagnostic routine, got pulled into a fence as the first wheel locked on the main road, bloody lucky they werent killed...

[MarkGolf 6]

I'll get a pic now!

I have no ABS. With engine running I can pump the pedal and it doesn't get any harder at allllllllll..

I just find it hard to believe I've got 2 dead M/C but then as I've said, I did have 2 dead fuel pumps! lol

[MarkGolf 6]

Here's the 23mm.. 22MM one on the car now..

[Scott 0]

a quick test of an mc when off the car, pull the piston out to the not acting position, block the end port, and push the piston back in, it should resist strongly and build air pressure at the end port like a bike pump, thats all it is.

If no pressure is created, the piston sealing o-ring has gone or slipped out of the groove.

[MarkGolf 6]

With the one in the picture, I can block the end port and push the piston in and out and I don't really feel any resistance, I can feel my finger get sucked in a bit when releasing the piston but not much..

I got told that Brembo 4 pots are prone to air locks and the best way to bleed them is have them off the car, not sure how much truth there is in that..

Would the pedal still go firm if the seals were buggered on the M/C when the car is off?

Appreciate your help!!