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Hi all,
I need the idiots guides to changing the brake fluid on the rear brake. I have a one way brake drain and will also be changing the pads for sintered pads.
What I need to know is when I place the drain on the nipple and loosing the bolt, 1. Do I take the cap of the brake fluid container and if so does this not let air into the system. 2. If i do not remove the cap and empty the system, when I go to refill the brake fluid container will it not let air in?

As I previously said, I'm changing the rear pads, is it best to do this after or before changing the fluid, or even during the fluid drain?

Sorry to annoy but don't want to balls it up.
Thanks in advance for your help.
 

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Don't worry Doc, we're all idiots here!

Best thing to do is change both the pads and the fluid at the same time, though not exactly 'during' the pad change. The reason is that the new pads will have more material on them and will actually mean you need less fluid in your system. In answer to your questions,

1. Yes. It will not let air into the system if you keep the fluid topped up so that the master cylinder is completely submerged.

2. You will have a job emptying the system if you do not take the cap off.

I have used various brake fluid 'tools' but by far the best one is common sense. Even without any bleed tools, simply connect a pipe from the bleed nipple to a waste container, pump the brake lever three times and hold down, then open and close the bleed valve for a second. Repeat this as many times as necessary, keeping the fluid reservior topped up, and you will have changed the fluid (arguably there will be some residual old fluid in the system but if you are this picky you may as well dismantle the whole thing).

Remember when fitting the new pads you will be pushing the slave cylinders further in than they were for the part-worn ones so some fluid will be displaced...increasing the level in the reservoir. To keep things simple, remember that with the brake pedal released the fluid is free to go back up the system into the reservoir.

Depending on when the brakes were last serviced, it may be worth rebuilding the calipers. I've done this job on my steamer and ended up having to buy a new set of pad retaining pins (the heads can get chewed up when trying to remove them if they are corroded). If you chose to do this job, you might as well replace the piston seals and clean up the pistons, sliding pins etc, at the same time.

Hopefully the retaining pins/bolts will come out easily enough so if that is the case, it is a relatively simple task to replace the pads and bleed the system but it's always worth cleaning up the accessable surfaces of the pistons with a toothbrush and some brake cleaner whilst you are in there.

Good luck!

Jon
 
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