Problem after new discs and pads, please help!

[Steely]

Right the past week ive had all 4 calipers off the car, to give them a lick of paint, and the braking system the once over,

The problem i have is since:

Ive bled all the system, rear calipers, front calipers and master cylinder,

took it for a spin, felt very much like new disc and pads would, need a little run in,

MY problem is:

Ive got a constant hissing from the brake pedal, actually at the pedal,, But its only when i press the brakes, Im sure its vac related, since it affects the tickover of the engine,

Sometimes it'll brake well and stop the car no problem and at the same time the hissing goes away, but sometimes you'll press harder on the pedal and it wont slow the car any quicker, at the same time the pedal is hissing

Im 100% the hiss isnt a leak, more just an operational noise, but before it used to hiss just for a second or so on take up, which it does odd times,

Is this still air in the master cylinder? i know for sure the caliper lines are clear of air,

Im due a long haul to milton keynes tomorrow so any quick advise would be a godsend!

 

[james walker]

did you bleed the 2 nipples on the master cyslinder?

 

[gb]

have a look here
http://www.seatcupra.net/forums/showthread.php?t=199990

 

[techie]

Sounds like a brake servo issue to me.

 

[Steely]

have a look here
http://www.seatcupra.net/forums/showthread.php?t=199990

lost mate? i have the discs and pads, more im struggiling with them working,



Being a servo problem , why would they work fine before hand? I dont understand why sometimes the pedal will hiss and other times its wont,

If i pump the brakes it clears, leave it a while and its back,

Cheers for the help guys!

 

[techie]

How much pedal travel do you have and how did you bleed them out?

 

[james walker]

did you pressure bleed or pump pedal?

if you pumped pedal then you may have rolled the seals in the master cylinder

 

[Steely]

Pressure bled all the calipers up, then did a final check using pedal method, didnt pressure bleed the master cylinder though, which may be the culprit

Rolling the seals in the master cylinder? what would this cause?

Im leaning towards air in the master cylinder, which ill have another look at tomorrow,

 

[AntneeUK]

if you pumped pedal then you may have rolled the seals in the master cylinder

Read on the Mk4 Golf site that is this a misnomer. Haven't found anyone who has actually done this, seems like an urban legend. Anyone here done it?

 

[libiza2007]

Yep me unfortunately! To eager to get rear calipers done, bled system via pump method, big mistake!! Garage tried everything afterwards, but to no avail. New master cylinder needed, but that'll teach me ey!

 

[AntneeUK]

Oh dear. Fair enough. Kinda gutted to see it is a real issue though!

 

[Disco_Mikey]

Read on the Mk4 Golf site that is this a misnomer. Haven't found anyone who has actually done this, seems like an urban legend. Anyone here done it?

I have never ever seen this done. Been a mechanic for nearly 7 years now, never pressure bled brakes (or clutch hydraulics for that matter) and never seen it...

 

[AntneeUK]

Well the Leon definitely isn't simple to bleed the brakes (I know!). No end of people appear to have had problems with it, including brake specialists

 

[Vin-R]

Hi! My pads and discs need changin soon, do u have to bleed the brakes

 

[james walker]

I have never ever seen this done. Been a mechanic for nearly 7 years now, never pressure bled brakes (or clutch hydraulics for that matter) and never seen it...

bill (badger 5) may have an input on this... its happened to him

 

[james walker]

Hi! My pads and discs need changin soon, do u have to bleed the brakes

no not really.. unless the fluid is due a change

 

[Steely]

Day 2 :

Im going to get to the bottom of this today, just bought a 2 metre length of neoprene tubing (clear),

Like i said before im thinking its the master cylinder which still has air locked somewhere,

In theory i would of thought using a longer bleed pipe and a bit more fluid will hopefully eliminate it if it turns out this isnt the problem,

I know brakes can be a pain in the arse, but this one takes the biscuit!

 

[Vin-R]

Cheers james, im on 70k, not sure wen thefluid will need changing? Ill just do discs and pads for now

 

[robertj]

Cheers james, im on 70k, not sure wen thefluid will need changing? Ill just do discs and pads for now

Fluid should be changed every 2 years. If you have a full service history then the garage would have done it as and when it was due.

 

[Steely]

Another question, It appears the hissing is a vac leak somewhere in the pedal area,

When it hisses, the braking efficiency is poor,. which is to be expected

but its not all the time now, if i pump up the brakes it'll stop leaking vac,


any ideas why id have a vac leak around the pedal area?