Brakes needing bled ?

[Jeff fae Scotland]

Hi guys, Some of you know im a disabled driver with a hand controlled brake lever anyway,I got new brake pads fitted all around

But feel the brakes need bled.If i pump the brakes with the engine off,a couple of pumps later the brake pedal goes hard.

Its the same when the engine is switched on.My question is,How do i know the brakes need bled.Do you pump the pedal

with the engine off or,with the engine on to see if you get a better pedal......thanks in advance.

 

[Gerg]

Hi, replacing the brake pads wouldn't normally be a reason to bleed the brakes, as you probably know.  The brakes are assisted in their operation by a vacuum servo, when the engine is off a reserve of vacuum is stored, but only enough for 2 - 3 brake operations.  After that you are operating the brakes without servo assistance.  Again, I'm only mentioning this in case you didn't know!  The brakes would normally be tested for 'feel' with the assistance working.

Unless the brake hydraulic system has been dismantled recently or there is a fault, then bleeding the brakes is usually a precautionary measure to remove any moisture that has managed to enter the system.  This can eventually cause internal rust if left and, more importantly, lower the boiling point of the fluid, which can cause a vapour (gas) bubble if the brakes get really worked hard and the fluid boils.

If the brakes feel more spongy after a set of pads has been fitted, this can be because the pads need to wear to the profile of the disk rotors that they are bearing on (which didn't get changed?).  This can take a few hundred miles or so.  The disks will always wear more near the centre, so in cross-section they will become tapered with use.  New pads have to adopt that wear pattern (i.e. bed-in), and before they do they can feel spongy as the pad loading is concentrated on one area, instead of across the whole pad surface, causing flexing, which appears as sponginess at the pedal.

I would imagine that when applying the brakes with a hand control there is a subtlety that is lost when using a foot, so you notice these things more.

Brake fluid is normally changed every 2 years as a service item, if it's been longer than this perhaps get them bled anyway.

HTH