almost like "brake failure"

[pete_clio]

this has happened a few times now...

its only when the car has just been started, driving a bit, foot on the brake, and very little happens, but then the brakes come back fairly quickly to how they were before. no wanring lights on or anything at all.

any ideas what might be causing it, as its not the most pleasant thing to happen coming up to a t junction lol

pete

 

[Henry]

when you say very little happens, is the pedal sinking to the floor or does it feel very stiff?

 

[pete_clio]

feels normal but theres little bite, and if you push it down harder theres a little more bite, but it only happens every so often, not everytime its started etc

 

[Henry]

from your initial description, i wondered if it might be servo related (which would give a very stiff pedal) or master cylinder failure (which would give you a very soft and completely ineffective pedal)

master cylinder seems a candidate but you might expect the pedal to feel different to described

have you had a good look at the hoses and unions to make sure you've not got a leak anywhere?

 

[pete_clio]

no prob ill do that tonight when i can get it into the garage! also just noticed that it seems to be coming form the back brakes...is a noise like they are rubbing off the discs even when handbrake is fully let off.

 

[David Ramsey]

Sounds like a vacum problem with the servo

 

[pete_clio]

how do you go about fixing that?

 

[rctempire]

Ruffstuff had a problem like this on the last Scottish Road trip, they bled the brakes a week prior to the event as he fitted new lines and brakes.

Turns out that there was air in the system even though the brakes had been bled properly on the first occation.

Ask RufStuff or Ali.

 

[Henry]

i don't think it's going to be the servo - you would definitely notice that the pedal was much stiffer if it were.

it sounds as though you'd be best off starting by having a really good look at the hydraulic system - start at the master cylinder and follow each pipe to each wheel, check the calipers and the discs and pads. you're looking for evidence of fluid leaks or any other problems. if you can't find any external leaks or any other obvious causes, i'd be inclined to suspect the master cylinder.

the noise from your rear brakes might be a sticky handbrake mechanism/cable by the way.
.
having said all that, i don't know how the ABS operates on these - is it possible it could be a fault with that?

 

[Henry]

Ruffstuff had a problem like this on the last Scottish Road trip, they bled the brakes a week prior to the event as he fitted new lines and brakes.

Turns out that there was air in the system even though the brakes had been bled properly on the first occation.

Ask RufStuff or Ali.

that's a good point - has anyone been tinkering recently?

 

[pete_clio]

on mine? nope last thing done was new rear pads 2 months ago, worst friggin pads ive ever used, so dusty and half gone too

 

[Henry]

^that's another symptom of sticking handbrake mechanisms/rear calipers.

also, it'd be worth bleeding the brakes and renewing the fluid before condemning the master cylinder (they're a b*gger to get at on these too ).

 

[rctempire]

on mine? nope last thing done was new rear pads 2 months ago, worst friggin pads ive ever used, so dusty and half gone too

I would bleed the whole system and top the fluid up as you go along. Its the only answer as if you have changed pads, you should really bleed the system after to make sure no air is in the system now.

Also make sure you bleed the system correctly, not just wheel after wheel, there is a specific way of doing it.

 

[pete_clio]

interesting! cheers guys il look into gettin new fluid into it. as im fairly certian itll not have been done since it was bought new