Help with brake bleeding

[Iaitoo]

So how long does gravity take?
More specifically when bleeding brakes. Seems to take forever. Think it's been 45 mins and no fluid out by the caliper. Can't remember that it took this long with the broken one(Before I knew it leaked). Disconnected the line from the caliper to free it up, but still no go.

[zx_volcane]

Someone tag Newton

[Iaitoo]

haha please. But still a slightly serious question
Anyone done it before that can say how long it took before fluid came through? Bit weird if it has clogged itself when it went through a week ago?

[Frosty]

Best to get someone to give you a hand. Get them to press the pedal then you open the nipple then close it, pedal up then back down etc. Keep doing that till you get down air out. Just don't pump the pedal too fast as can damage the master cylinder seals.

[Iaitoo]

So its ok to use the pedal on an empty system as long as I do it slowly? I'll try then..

[ConorTRG]

Don't push the pedal all the way to the floor you can damage the seals in the master cylinder.

[Martin306]

Of course it's okay. the master cylinder won't be totally dry if you're putting fluid in from the top!

[adam b]

Gravity doesn't exist. That's your problem

[DeeTurbo]

Did you leave to top off?

[Iaitoo]

Left the top off

[Iaitoo]

Ok, so got fluid out on all the corners. Sometimes when the GF press the pedal, lots of fluid comes, and the next time almost nothing. Is this because of air pockets? Tried going all the way round, but pedal is still going to the floor  How much brake fluid is it supposed to hold? Maybe used 1/2 litre. Bit more.

[adam b]

Easy put half a litre through, if you have abs it might take more

[Toms306]

Are you closing the nipple before the other person lifts the pedal? If not, the air gets sucked back in, so next press you're just pushing that air out again lol.

I find it's much easier with a one way valve in the pipe, can get them cheap over here, 'one man bleeder kit' but maybe not readily available near you.

[Iaitoo]

Used my one man bleeder kit. (got em here as well) and that worked perfectly. Actually got brakes now. Bit unsure on one of the rears. Cause some fluid was leaking behind the bleed nipple and not just straight through the pipe. If brakes are bad. Is it enough to just bleed that one, or do I have to do em all again? Its the left side, so not the furthest away from MC.

Edit: They work. Feel a bit soft. Been off the road for a while so can't remember how it was, but they have always been a bit soft. When the car is turned off and I pump the pedal it gets harder than before and does not move. Can I asume that the bleeding is ok?

[insomaniac45]

if they have gone rock hard and not spongy then all should be good

Having fluid leak behind the nipple is common and nothing to worry about (only when bleeding the system with the nipple undone)

[Paul_13]

If you've got abs you'll probably need to trigger it to release trapped air

[Iaitoo]

Not rock hard while engine running. Just when pumped when engine off. Bit soft when engine running. But does brake. Was soft before as well tho. Not sure if its worse than before And no ABS  Not sure if I think it feels spungy, but have to press the pedal pretty far in before it brakes. But when it brakes, it brakes.

[pug306driver]

Hi iaitoo,

If the master cylinder has been allowed to empty, ( or a new one/resealed on fitted ) then its best to prime it first of all, by filling the res and allowing some dripping to take place from the m/cyl pipe union holes, caught with rag.

When you are sure the cylinder is primed, say 20 drips form each hole, fit pipes ( they should be ready to fit and in place, only needing to be screwed in and tightend ) and  tighten, washing any fluid spillage with water. The m/cyl is now very wet with fluid inside and ok to use the pedal.  

Remember that the master cylinder is a pump, pumping fluid out, which, when the system is up and running, is returned to the master cyl res, apart form the fluid "used" during caliper self adjustment.

Since the pipes from the m/cyl to the abs unit are above the level of the m/cyl, then undo the feed pipes on the abs and prime them also, after that ( possibly undo the pipes from the abs unit to wheels and watch for fluid dripping, then do up tight ) it should be all down hill, apart from possibly the feed pipe from the abs to the r/h/s of car.

If when replacing pipes, some "pipe end caps" ( flare for cap formed on scrap pipe, union fitted and "open end of pipe flattened and folded thus sealing" ) are fitted, the cylinder will not empty, and gravity ( syphon ) can change the fluid for you, drip by drip.

With a sucker ( dedicated hydrometer body minus float, just for brake fluid only ) most of the old discolured fluid can be sucked out from  the res.

Add new fluid to res to "disturb" any black crap in the res and suck it out, add some more new fluid and repeat until only clean fluid is sucked out. From this point onwards, only new clean fluid is making its way thru the system, pushing old fluid out.

If fluid is caught in a jar, and after say 200 drips for the furthest nipple, the old fluid is emptied and  new fluid collected, you will see the new fluid cos of the colour change. New looking rather than discoloured

Alternatively, a pressure fluid feed to the m/cyl res will prime and fill the system to the bleed nipples.

There is a tiny tiny hole in each chamber of the m/cyl which allows fluid to flow by gravity, which if blocked, will not allow gravity flow to happen. This hole is not seen unless the res is removed, but if the caliper pistons can be pushed home, and the fluid level in the res rises, then this hole is clear. If this hole is blocked, then you will have trouble bleeding the system and the brakes will tend to not want to release, in fact, will lock on and stay on until system has cooled down.

Make sure the holes in the bleed nipples are clear, else they will not pass fluid.

Engine off and all vacuum used by pumping the pedal several times, allow to rest. If pedal now hard when pressed, a good hard short travel pedal means no air in system, a spongy pedal means air still in system.

With pedal pressed and engine started, the brake pedal goes down more, means vacuum and servo works. Check for leaks on pipes, unions, calipers, master cylinder to servo and res to master cylinder.


You say you have to press the pedal quite far before brakes work, how far, ours has abs and brakes very keen with not much pedal travel, powerful brakes but had brakes serviced xmas time, new pipes, new hoses, new discs, new front caliper seals and all calipers/pads lubed. (slide pins and pad slide contact areas )

[Poodle]

If the pedal still has a lot of travel after bleeding you've probably got a sticky caliper/wheel cylinder/handbrake mechanism.