Pad change/bleeding brakes

As my previous question has slipped the net.

If you clamp the hose, open the nipple and push/turn the piston back, is there not a chance that air will get into the pipe? Is it never necessary to subsequently bleed the brakes or can you just assume it will be OK?

Andy C

Reply to
Andy Cap
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for the time it takes its aways sensible to bleed the brakes when chaging pads or shoes , infact i usally change the fluid at the same time

Reply to
steve robinson

if the flexible pipe is a suitable type (some modern ones are a very stiff type that should not be squashed) then clamp the hose, brush around the nipple and remove the nipple completely (take care that debris from around the nipple does not fall into the caliper bleed hole) and clean the threads of the nipple, grease the nipple threads to stop air leaking past the threads during the bleed operation (actually unlikely, but good practice) and screw the bleed nipple back into the caliper, place a foot or more of clear plastic tube on the bleed nipple, keep the plastic tube rising vertically from the caliper for a few inches or more and either put the loose end in a jar or let it hang clear of mechanical bits. smoothly press the caliper piston back into the caliper (tutning if appropriate) the fluid will go up the tube, when you stop pressing there will still be fluid above the nipple so no air will go back in, tighten the nipple, rebuild as necessary and check the nipple tightness when the caliper is bolted back on. remove hose clamp (can be easily forgotten if out of sight, I have !)

Reply to
Mrcheerful

I used to install spring-loaded self-operating bleed nipples on my cars many years ago, are they still available? They made one-man bleeding a simple operation.

Reply to
Davey

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Reply to
Duncan Wood

Thanks for the explanation.

Reply to
Andy Cap

snip

Mine weren't made by Ducati or Brembo, and they certainly weren't metric, but they did the job. I couldn't understand why everybody I knew didn't fit them, they made the job so easy.

Reply to
Davey

Just thinking out loud ... Whilst those things seem like a good idea, aren't they reliant on there being an air-tight seal between the nipple and it's hole for them to work properly?

eg, I can understand how they would allow fluid to be pumped past on the brake pedal down stroke (and some brake fluid might make it into / past the nipple threads) but wouldn't it be quite easy to get air back in the same way on the up-stroke?

Even using the 'old fashioned' two man ... apply slight brake pressure

- release bleed nipple till pedal hits the floor - nip nipple - allow pedal to lift - repeat till free of air or old fluid purged etc, there is never the chance of air getting back in?

If the auto nipple had an 'O' ring round it, sealing it, then that would work ok?

Maybe they would be fine for the initial stage (bulk air removal on a complete system strip) and then they could still be used as above for the final stages (ignoring pressure bleeders etc). ;-) [1]

Cheers, T i m

[1] Mate made a pressure bleeder from a unwanted pesticide pressure spray. ;-)
Reply to
T i m
[...]

That's no different from using normal bleed nipples and conventional bleeding techniques surely?

Mr C advises greasing the nipple's thread for that reason, although I've never needed to do that so far.

Chris

Reply to
Chris Whelan

Yes, that was what I was saying ... + some?

Doh, missed that bit. (I generally use Coppaslip so I assume it would work the same way re air etc)

So, my suggestion was that you could use both. Use the valved nipple for the bulk / single handed phase and then (even that nipple) could still be used as per std nipple at the end. Using the valved nipple would mean you don't need a tube with valve or keeping it up / immersed etc.

Cheers, T i m

Reply to
T i m

using a clear tube allows you to see even the most minute bubble and the colour of the fluid, letting the fluid dribble down the caliper from an open nipple gives you very little idea of the state of what is coming out.

Reply to
Mrcheerful

Agreed and why I have never bled brakes 'tubeless'. ;-)

Previously I've used the little clear tube with the rubber connector at one end and the weight and split at the other but now just make my own.

On motorbikes it's generally easy to do the job on your own but under a car, anything that makes the job easier is welcome (even if it is up on a 4 poster). ;-)

Cheers, T i m

Reply to
T i m
[...]

Some motorcycle brakes, especially off-road ones, can be a bugger to bleed.

The best method I've found is to use a large hypodermic syringe to create vacuum at the bleed nipple.

Chris

Reply to
Chris Whelan

when I was in the Suzuki workshop we found that bleeding to the master cylinder was often the best way, just tickling the lever allowed the air back up and out, best of all you can easily see the relevant holes with the master cylinder open, when no more bubbles come, just a few squeezes would sort out any trapped bubbles at the caliper (through the bleeder or the hose) if the lever did not feel perfect after all that then we tied the lever to the bars with inner tube rubber bands and left it overnight.

I do have a dedicated vacuum brake bleed kit, but 99 times out of a hundred (on cars) I just bleed them manually, usually on my own.

Reply to
Mrcheerful

Yup, done all that as the front line is often nearly vertical.

Cool. ;-)

Cheers, T i m

Reply to
T i m

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