Bleeding Brakes

[SilR44]

Hey guys,

I've done some searching but couldn't find anything that gives detailes instructions to bleeding brakes. My master cylinder recently went bye-bye and I think its cos of the way I bled the brakes when I changed the pads.

When bleeding the brakes, are you supposed to hold the pedal flat to the floor then release etc? I remember reading a thread in here stating that if you hold the pedal flat to the floor you'll blow an O-ring in the master cylinder , which is exactly whats happened......

Can anyone give me some advice with this?

Cheers

Matt

[steve_gts4]

it will gravity bleed. you dont need to touch the pedal at all. just be patient

[gtrchick]

Peh to gravity bleeding...

Bleed from the wheel furthest away from the master cylinder ie. Left rear, right rear, left front, right front.

You can press the pedal all the way to the floor, but do it slowly as if you bleed them to fast it can cause your cups in the master to have issues.

Say you're pressing the pedal, for eg 15 pumps, hold the pedal down, (its good if you get someone to help to reduce the chance of air getting into your system) then lock up the nipple, then pump up the pedal, so that it goes hard, and hold the pedal down, and crack the nipple, your pedal will go to the floor doing this as it releases fliud again, then lock it up, its just a precaution to make sure air really isnt in the system. Oh an make sure your reservoir doesnt hit below min.

[MANWHORE]

steve, tell me you're joking?

[discopotato03]

I've seen mechanics renew fluid by the gravity method and it worked fine , have not seen it done on a Skyline . I don't know about it bleeding air out .

I have seen old masters stuffed by using the full stroke when bleeding the system . I believe if there's a lip on the master bore and the seals are pushed past it they can tear and not hold pressure . I would not stuff about with a worn master cylinder , its your life and that of others that depend on it working properly .

Cheers .

[gtrchick]

No offence but you wouldnt go out and flog the hell out of your car if you have just been fiddling with brakes!!! you can EASILY check to see if the master cyl or brake booster is stuffed. Its all in the feel of the pedal. The cups will only push past the lips if there is a serious lack of fluid (LEAKS) in the primary cylinder.

I've bled the brakes on my 32 heaps of times and nothing is rooted on them. You'll be fine. And if something does break than better it breaks while its on stands and you arent driving then one day you're doing a mountain run and then oh sugar where are my brakes....

Edited November 1, 2006 by gtrchick

[discopotato03]

No offense taken , my point is that using the full stroke of the master cylinder when bleeding brakes pushes the pistons and cup seals further into the cylinder than normal running use .

Yes I do know what a spongy pedal feels like and no I don't flog the hell out of cars on the street because I have this thing called mechanical sympathy .

Cheers .

[Cubes]

I tend to go a little overboard when bleeding.

I use 2 bottles of brake fluid, the usual castrol red bottle. I tend to steer clear of the synthetic stuff in the old R32's.. The synthetic stuff doesn't lubricate as well, especially in clutches. If I rebuilt all callipers and master cyl I would only thrn feel comfortable running synth fluid.

First I always remove the fluid from the reservoir refill and drip bleed the reservoir.

I then have it drip bleed from the furthest point even if those pads aren't being changed.

The pads that are being changed I crack the nipple and push the piston all the way in with a g-clamp.

Before removing the g-clamp I drip bleed for a little to get the old fluid out then nip up the nipple.

Drop the pad in and pump the brakes a little to bring the piston back out. I then drip bleed that same calliper again.

Then on to the next and do the same.

I've never had any issues doing it this way in the past 5yrs I've owned my 32, BUT I'm good at not letting air in to the system.

If you let air in to the system you will need to bleed the system via the usual pedal method.

An old mechanic friend said to always crack the nipple when pushing the callipers cylinder in as it can damage the master cylinder. If this is possible.. I really have no idea. My thinking is its silly to do so anyway as its pushing old hammered fluid back in to the line when you could be pushing it out in to your jar.

So disco.. The drip bleed method on the 32's at least work really well.

I can't say I've ever driven another make car with a better brake feel than mine. I've driven an R33 and that felt the same, the initial free play of the pedal is progressive and graby, the pedal is then solid and from hat point onwards its easy to jab the brakes and have all 4 lock. At no point did either mine or the R33 feel as if I was struggling to pull up, i.e lots of force on the pedal without overcoming the tyre grip.

A good example of poor brakes are VL or VN Commodores. Those things feel like your almost touching the floor pan on hard braking.

[gtrchick]

No offense taken , my point is that using the full stroke of the master cylinder when bleeding brakes pushes the pistons and cup seals further into the cylinder than normal running use .

Yes I do know what a spongy pedal feels like and no I don't flog the hell out of cars on the street because I have this thing called mechanical sympathy .

Cheers .

Doesnt mean that pushing it further than in normal running use is going to cause damage. Possible yes, but atleast there will be very little chance of air in your system.

And i never said you didnt know what a spongy pedal feels like. and i never said you do flog cars. I just said thats its best not to do that after fiddling with brakes.

Thanks

[discopotato03]

Agreed .

[Cubes]

And i never said you didnt know what a spongy pedal feels like. and i never said you do flog cars. I just said thats its best not to do that after fiddling with brakes.

Thanks

I'm sure following the correct bed in procedure would soon show if there were any issues.