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poor feel in brake pedal
AndyW - 30/6/13 at 08:43 PM

I have a sierra master cylinder which was new. I have bled the brakes, but the pedal feel spongy and when I dove up the driveway today the brakes seem almost non existent. Any idea's to what it could be, could there still be air in the system, although in have bled the twice To make sure. also the handbrake only comes up two clicks. Is it just a case that it all needs adjusting on the rears (drums) and the fronts need bedding in?

thanks

andy

britishtrident - 30/6/13 at 09:19 PM

If you bled it properly then it points to a leak at union. Don't expect to see obvious leaks of fluid go round them all cleaning them and examining them and examining them using a torch while somebody pushes the pedal hard.

rusty nuts - 1/7/13 at 06:27 AM

Back off the handbrake adjuster until you have loads of slack , remove brake drums and manually adjust the auto adjuster on each brake shoe one click at a time refitting the brake drum between adjustments until nearly all of the clearance between the shoes and drums is taken up.Your problem may well be as simple as adjusting the rear brakes to sort it out

AndyW - 1/7/13 at 06:56 AM

Thanks guys,
I will pop the drums off and have a peek, will report back...

daviep - 1/7/13 at 07:05 AM

You need to try and identify the problem in a methodical manner, use a pipe clamp on flexi hose to try and isolate which corner / end the problem is with. I would be expecting it to not be fully bled or a calliper which is stuck and flexing the disc or pad.

Cheers
Davie

adithorp - 1/7/13 at 09:06 AM

Did you bleed the brakes with the drum adjusters fully let off? If not the pistons will be out a bit and that can let a bubble of air remain in them.

Let the adjusters and h/brake cable off, bleed, then manually adjust the "auto adjuster", then h/brake cable.

davidimurray - 1/7/13 at 09:10 AM

Have you got enough push rod travel ? I spent months chasing the problem with my brakes. Sierra M/C has 30mm of travel at the push rod and you must be able to use all this without the pedal hitting the bulkhead. Mine had about 23mm of travel and would go hard but could just be made to touch the bulkhead using all my might. Extended the push rod and with about 26mm of travel the pedal went solid.

Also do you have a hydraulic brake switch? If so make sure the contacts are at the bottom or side with a T and a bleed nipple as trapped air in the switch can cause a spongy feeling.

britishtrident - 1/7/13 at 12:23 PM

Extending the pushrod will lead to trouble if you are not very very careful !

As I said at the start before you do anything check for leaking unions.

chrisni1986 - 1/7/13 at 08:42 PM

leaks or failing that try and borrow a pressure bleeder, ive seen problems in the past with it being hard to get a good pedal, one bleed with the pressure bleeder and wham there it was!

AndyW - 1/7/13 at 09:10 PM

quote:
Originally posted by chrisni1986
leaks or failing that try and borrow a pressure bleeder, ive seen problems in the past with it being hard to get a good pedal, one bleed with the pressure bleeder and wham there it was!


I used a pressure bleeder