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        General >> Problems >> Soft Brake Pedal (Scary)
        
(Message started by: Scorpio_Sam on Sep 5^th, 2005, 3:36pm)

Title: Soft Brake Pedal (Scary)
Post by Scorpio_Sam on Sep 5^th, 2005, 3:36pm

Hi Fellas, after taking on the not too bad a job of replacing the rear discs and pads I came to expect a soft pedal but this is Strange. The brake when applied very slightly starts to work as it reaches its original braking position and you feel the car slow slightly, then I have a massive drop until the the brakes finally work, now if I pump the pedal once i get the brake further up the pedal and if I pump it once again it feels pretty much as it should be, I didnt disturb the brake lines so no air has got in, could it be that the rear caliper piston needs winding out or something similar ? I have noticed that the handbrake is a little higher than normal but it is holding the car ! any Ideas would be appreciated. ???
Cheers

Title: Re: Soft Brake Pedal (Scary)
Post by howiedintheplace on Sep 5^th, 2005, 6:50pm

Hi
Well I know you say you didn't disturb the brake lines but it does sound like you have air in the system.
Check what you have done & bleed would be the first thing to do.
You did not touch the front's then?
The rear calipers will adjust them selves as long as they are in good condition & you have no air in the system.

Title: Re: Soft Brake Pedal (Scary)
Post by mr._floppy on Sep 5^th, 2005, 8:15pm

If you've disturbed the calipers or replaced pads you'll need to pump the pedal fairly hard for a few times to bring the pistons and pads into correct contact with the disc. Apart from that, are you sure you have fitted the ( correct ) pads correctly or neglected to tighten the securing bolts

Title: Re: Soft Brake Pedal (Scary)
Post by Scorpio_Sam on Sep 5^th, 2005, 9:20pm

Thanks Guys, I will take a look and see if I can pump the pedal up some more, then check the bolts are tight, apart from that I remember the pistons screwed back in fine so i would hope they would find their own position. Last Lets see Cheers

Title: Re: Soft Brake Pedal (Scary)
Post by mike.g on Sep 5^th, 2005, 11:54pm

hello,

I changed my front pads and discs about 3 months ago and had exactly the same sympton. Brakes feel soft and you need to pump the brakes about twice to get the original feel. If left for a minute the brakes are soft again but if you brakes again straight away they are normal.

I changed one side first.

When I checked the side I had done against the untouched side I realised that I had not put back the spring correctly. It was a very minor difference and one I might not have noticed unless comparing the two.

Title: Re: Soft Brake Pedal (Scary)
Post by Scorpio_Sam on Sep 6^th, 2005, 6:55pm

I checked the brakes again today and found a lump on the back of the new pads, this was interfeering with the Castalated piston, so I ground them off. With all my efforts again the pedal is soft with 2 pumps to get it right.
What am i doing wrong ??? :'(

Title: Re: Soft Brake Pedal (Scary)
Post by Oliver on Sep 7^th, 2005, 11:01pm

The "lumps" on the back of the pad facing the caliper piston are supposed to engage in the slots on the piston face. Which means that when winding in the piston it should end up with the slots vertical and horizontal with respect to the caliper.

Grinding off the lugs on the back of the pad may not have been a good idea as I suspect their purpose is to prevent the piston from rotating. This may be related to the operation of the handbrake.

Oliver

Title: Re: Soft Brake Pedal (Scary)
Post by martin_rowe on Sep 8^th, 2005, 8:44am

you are correct, the lugs need to locate in the caliper, better swap the pads round befor they get too bedded in to the disc.

Title: Re: Soft Brake Pedal (Scary)
Post by howiedintheplace on Sep 8^th, 2005, 9:13am

Scorpio_sam
I don't understand why you would think them lumps should not have not been there? Did your old pads have them? Have you got a pic of what you have done.
As said there should be a locating lug on the pad to lock in to the face of the brake piston. ???

Also does the pedal keep going soft after you have pumped it or use the brakes?
If so list everything you have done to the brakes.

Title: Re: Soft Brake Pedal (Scary)
Post by mr._floppy on Sep 8^th, 2005, 9:47am

I feel it's an "air in the system" prob. It just takes one caliper or hose to have air in it to give the pedal a soft/spongy feel.

BTW I don't recall any raised bits on the back of my rear pads, smooth as the proverbial.

Title: Re: Soft Brake Pedal (Scary)
Post by martin_rowe on Sep 8^th, 2005, 1:13pm

there should be a raised lug on all 4 pads, its used on just the outersto locate in the piston

Title: Re: Soft Brake Pedal (Scary)
Post by Oliver on Sep 8^th, 2005, 3:52pm

on 09/08/05 at 13:13:49, martin_rowe wrote:

there should be a raised lug on all 4 pads, its used on just the outers to locate in the piston

I think you meant the inners. The other thing to check is that the calipers can slide freely back and forth on the pins (floating calipers). If they are (partially) seized then the pads will not be making contact on each side of the disc with equal pressure until you have forced them together by pumping in the brake pedal. Similarly, although the pads should be a snug fit, a smear of copper grease where they make contact with the caliper is advisable.

There will be a logical explanation somewhere, it's just a matter of finding it!

Title: Re: Soft Brake Pedal (Scary)
Post by Scorpio_Sam on Sep 16^th, 2005, 12:36am

:-/ Hi guys, yep i ground off the lump on the face near to the piston, I must say that now it only takes one good pump to get a real positive feel but still the same after 3 seconds the pedal returns to spongy. I cleaned the guides and the pads moved freely, not too loose ! I cant see the advantage of the lump on the rear of the pad as it will stop the piston rotating out to take up the slack but at the same time I must admit I havnt bled the brakes just to make sure. Stop a minute, if its air then the problem would remain the same yes, but since i ground the lug off the rear of the pad then the pumps to get it to work properly has gone from 2 to 1 ???

Help !

Title: Re: Soft Brake Pedal (Scary)
Post by Oliver on Sep 16^th, 2005, 7:12am

on 09/16/05 at 00:36:38, Scorpio_Sam wrote:

I cant see the advantage of the lump on the rear of the pad as it will stop the piston rotating out to take up the slack but at the same time I must admit I havn't bled the brakes just to make sure.

The piston is not supposed to rotate when in use, only when retracting back in before fitting new pads. The automatic handbrake adjustment may not be working properly now. If I were you I would get some new pads and fit them properly. The lug on the back of the pad is there for a purpose and not just to cause a nuisance!

If you think it feels like there is air in the system then I would bleed it anyway. It should be done regularly as part of a service in any event as it absorbs water. Ask Snoopy about this. He's a strong advocate of fluid replacement and knows why. (Having said all this I confess to not practicing what I preach!).

Let us know how you get on.

Title: Re: Soft Brake Pedal (Scary)
Post by martin_rowe on Sep 16^th, 2005, 8:23am

try your brake padal with out the engine running, pump it 4 or 5 times, leave it 30 secs & then press it, see how far it goes then, do not run the engine. if you have a good firm pedal the hydraulics are ok, if still goes down too far at first press then you have a fluid / actuation problem.

Title: Re: Soft Brake Pedal (Scary)
Post by Scorpio_Sam on Sep 17^th, 2005, 10:29pm

I tried the Pump the pedal with the engine off and leaving it for 30 sec,s and I must say if I had that pedal in normal operation I would be happy ! So now my plan is to swap the pads again, give them a quick bleed snd see what happens. I let you all know the outcome.
cheers :-/