Spongy Brakes

john-wingnut

john-wingnut

Active Member
Basically back in feb I bled my brakes and did pads etc.

They felt a little spongy but thought they just needed to bed in etc.

So I left them. In may they were still feeling spongy so I re bled them to make sure there was no air in the system. Zero came out, just fluid.

Any how now into July and they are still really spongy. I can put the brakes on and then continually press the brake to the floor :s

There is no leak and resevoir has stayed at the same level since feb.

The only thing I have noticed is when ever I press the brake pedal there is a strange noise from the engine bay. Like a mechanical creak, very weird.

Any ideas???

John
 
When you bled the brakes - did you bleed them in sequence, and kept the main brake fluid reservoir topped up with fresh fluid - DOT4/5 spec?
 
How did you bleed them John? There is a possibility that if you bleed at high pressure, the ABS unit can lock up and trap air inside it.

The best way I've found is to use a pressure bleeder that keeps around 20psi in the system and to use plenty of fluid.

Cheers,

Mike
 
I used a pressure bleeder, erm cant remember the pressure but ive bled them twice and they still feel naff!!!

I did try and bleed the ABS unit using VCDS but it didnt seem to work correctly. Maybe thats what's messed it up

John
 
Might be a leaking master/slave cylinder seal? Normally they wouldn't allow the pedal to hit the floor, unless really bad, but it could be a cause.

Cheers,

Mike
 
Skipton01 said:
How did you bleed them John? There is a possibility that if you bleed at high pressure, the ABS unit can lock up and trap air inside it.

The best way I've found is to use a pressure bleeder that keeps around 20psi in the system and to use plenty of fluid.

Cheers,

Mike
Click to expand...

Just adding to Mike's theory, you need a minimum of 28psi to bleed the ABS unit. If you use a car tyre as the pressure source then its possible you start above that threshold but finish the bleeding process well under. On that basis, its possible the ABS unit is not fully bled and has air trapped inside. If thats the case it may also be the source of the noise in the engine bay.

Cheers Spike
 
There has been no loss of brake fluid so cant be a leak otherwise I would have seen the resevoir amount drop.

How much will a stealer charge to bleed the ABS unit??

John
 
Just because there's no external leak doesn't mean that there's no leak - it could be leaking past the piston back into the system, rather than into the pressurised part of the system.

Cheers,

Mike
 
O right got ya - did think about it like that!!!

My best option would be to get the ABS bled, then if that doesnt solve it, get a new master cylinder.

John
 
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