soft/low brake pedal

[Jxfwsf]

With the engine off, does the pedal pump up firm?
Give it a few minutes, is it still firm or does it require you to press it a few times?
If there are no visible brake fluid leaks, get someone to watch each of the brake hoses 1 at a time (the flexible black hose, 5 in total inc the rear body to diff) while you press the pedal, are any of them shot and expanding like a balloon?
Is it the firewall flexing 1"?
Are you using the cheap brake pads?

How do they test it over there?
Is it upto date using a calibrated machine that measures the vehicle speed, pressure applied to the pedal and deceleration of the vehicle?

Oh and you don't bleed brakes with the engine running, it's a simple hydraulic system, not trying to stop 2 tonnes with aid.

Not the case here, but if it's a 20 year old system, the last thing you want is the piston seals scraping through the buildup of crap in the bore and tearing the seals up. Only use half at most of the pedal travel to pump up and bleed (sit your other foot under the pedal so it can't go to the floor), you've probably seen the crap and buildup in a reservoir, now think about it sitting in the bore and a rubber seal running over it a few times where the piston seal normally doesn't go.

 

[pete30nz]

EDIT: my last message mentioned wheel was hard to turn. The caliper i had swapped to try had a sticky slide, which we freed up and wheel was turning fine again.
Also I clampped front brake lines and with engine running pedal was firm as, clamped rear hoses and with engine running pedal was not as firm.

Hi Jxfwsf,
I just checked the thread now.
Thanks for messaging.

Yes with engine off the pedal is high and firm as, and doesnt seem to change.
But start the engine and pedal is about half travel be for you feel any thing and soft.
With engine running yes it takes 3 or more pedal presses to start feeling better, but still spongy.

When you say about flexing, mite you mean is the booster moving forward as i pump the pedal? It doesn't move much at all since I refitted the bracket at front of master cylinder.

When they test the brakes at w.o.f shop they use the roller in ground system over here with a screen.

I'm using calibre brand brakes pads about $50 - $55

Next time we bleed the system, I'll get my mate to pump up the pedal but only pumping half way pedal?. Then does he hold down to the floor while i crack the nipple?


Thanks heaps

Pete

 

[the_boozer]

the only thing in this thread thats not all ready mentioned on things that can get fucked up with brakes maybe I only think its an issue because it had me fucked once, have you lost the reaction disk in the booster push the brake pedal in the the master cylinder off will do it. If the brakes bleed up nice and hard then go soft / spongy when the engine starts is the give away.

 

[Immortality]

If the brake pedal is rock hard with the engine off and then sinks when you start the engine there is a problem with the brake booster as it's loosing vacuum. If you start the engine and allow vacuum to built in the brake booster and then switch the engine off you should need to pump the brake pedal 3 or 4 times to deplete the vacuum in the booster and the pedal will go firm again. If you start the engine and allow vacuum to built in the booster and then switch the engine off the booster should maintain a vacuum. Simple test is to check the brake pedal after a short period, if the pedal drops as per normal then it's holding a vacuum, if the pedal is hard then it's got a vacuum leak. This unfortunately is fairly common on older cars. Most likely the one way valve is stuffed or worst case it is loosing vacuum via the push rod seal in which case the booster will need replacement.

All brake pedals will have some travel before the brakes actually start to work, this is good because it they came on as soon as you touched the pedal it would be bloody dangerous. the WOF guy is talking crap if he's comparing your 20+ year old Commodore to his new one. probably best to compare you brake pedal to another commodore of the same vintage.

IMHO cheap brake pads (that really aren't that cheap) from supercheap just aren't worth the effort. I did the front pads on a 2002 Subaru last week with decent pads from BNT and the retail price was roughly the same as the Callibre pads you put in and the bonus was a firmer pedal.

I use an old medical syringe to suck all the old fluid out of the reservoir and fill with new fluid before doing anything else. If it's real dirty wipe out with a cloth before re-filling.

If you don't want the pedal to fully depress to the floor find a bit of wood to put under the pedal. put car up on stands and remove all 4 wheels and then start bleeding at the wheel furthest from the reservoir working towards the closest one. Bleed each caliper until clean fluid comes out. Because you are doing a full bleed you will need to regularly top up the reservoir, if it runs empty and gets air into the system you will need to start over again.

Bleeding is simple, have your assistant pump up the pedal and then apply pressure, you then crack the caliper bleed nipple and allow the old fluid out, as the pedal drops and the flow reduces close the bleed nipple. Make sure your assistant does not release the brake pedal until after you close the bleed nipple or you will draw air back into the caliper and **** it all up again.

My boys are great assistants, commands are simple. Pressure and release. If your assistant can't follow those 2 simple instructions find another assistant.

Failing all this take it to a local workshop, (it hurts to type this) but your local Midas just might be the go.....

 

[Jxfwsf]

Try different pads, calibre really aren't that great (probably fine for the grand parents in their lil kia ducking down to the shops) and last time I tried a set it was a soft squishy pedal.
Although surprisingly they did pass a rwc test here a couple of years ago, new set of decent pads and the squishy pedal problem went away.

Was the same with a set of "repco" pads on a VT, tried flushing and bleeding the system trying to make it feel better with no success, threw in a set of slightly used bendix, magically no more squishy pedal.

 

[pete30nz]

Hi the_boozer,
I've never heard of the reaction disc, which leaves me asking where exactly does it sit.
I'll have a look and confirm if its there once I know where it sits.

Immortality and Jxfwsf,

I had the car in at safe r brakes and Pitstop,
Pitstop bled the brakes for me, unsure how they actually did it.

I'll try some new brake pads, other than bendex what are other good brands of pads you know of.
And I may as well try the half way pump while bleeding brakes to see if it makes a difference for me.

Thanks fellors for the replies
Cheers pete

 

[Immortality]

For your average daily run around I use and recommend the BNT Cplus in-house brand brake pads. They are a low dust ceramic formulation that work well and are reasonably priced.

 

[Jxfwsf]

If it's been bleed there is no need to do it again.
Just push the pistons back in (it won't be very far if the current pads are new) and won't do any harm just to fit a different set of pads.

 

[Brisbarnz]

Does it have abs?

 

[the_boozer]

Hi the_boozer,
I've never heard of the reaction disc, which leaves me asking where exactly does it sit.
I'll have a look and confirm if its there once I know where it sits.

http://members.iinet.net.au/~dattoman_1000/images/boost.jpg
Its inside the booster behind the push rod. Its probably too late and you all ready know by now I guess