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Flushing Brake Fluid & Changing Brake Pads

Discussion in 'Maintenance and Servicing' started by NatG, Jan 8, 2016.

  1. Hi everyone,

    So after a days/hours of researching forums and youtube videos, I still need advice! I am looking to change my brake pads and flush out the old brake fluid which is a dark brown colour.

    I have all the tools, oils and new pads and I also purchased a vacuum pump device for the brake fluid. My understanding (and not going into detail here) is as follows:


    1. Remove the 2 bolts from the caliper
    2. Remove the pin that holds it together
    3. Old brake pads slide out
    4. Clean pistons with a rag (gently) and perhaps a toothbrush if necessary
    *gently and very slowly without too much pressure pump hand brake so pistons come out a little more and clean as required
    5. Once pistons are clean, push the pistons back into their holes slowly and gently (may need a clamp if they arent going back in)
    6. Once pistons are back in their holes and are clean and shiny, insert the NEW brake pads in the same position as the old ones
    7. Place caliper back onto rotor and screw the pin and the 2 bolts back in
    8. Gently and slowly pump the hand brake lever so that the pistons come in and out and the brake pads re adjust themselves

    Can anyone please confirm the above is correct and or make suggestions/tips?

    Questions regarding the above:
    1. When cleaning the pistons, do I just use a rag or should I spray some brake cleaner on them also?
    2. Do I need to have the brake fluid reservoir (front) lid open when changing the brake pads at any stage?


    1. Unscrew the reservoir lid/cap and remove whatever is under (if there is anything). Obviously cover everything and anything in case of brake fluid leaks/overfills etc
    2. Insert the clear tube into the reservoir and suck out the old brake fluid into a container
    3. Once all old brake fluid has been sucked out, wipe out the inside of the reservoir
    4. Once clean and all fluid out, top up with new brake fluid
    5. Once new brake fluid is topped up, go down to the front wheel/brake caliper, locate the bleeder nipple, place my clear tube over the bleeder nipple (and before I open the nipple), i'll give my vacuum pump a few pumps to get the pressure going, then SLOWLY open the bleeder nipple. Let the old fluid release slowly and whilst doing that, continue checking the reservoir and DO NOT ALLOW it to completely go empty otherwise air will go inside
    6. Continuing on with step 5, if the NEW brake fluid in the reservoir is getting low (as I am flushing it out via bleeder nipple), top up again and continue steps 5 and 6 until clear and clean brake fluid is coming out of the bleeder nipple
    7. Close the bleeder nipple screw, remove my clear tube off the nipple and follow steps 5, 6 and 7 on the other side (if required)
    8. Top up reservoir with brake fluid

    Questions regarding everything

    1. Do I change brake pads BEFORE flushing reservoir fluid and caliper fluid or flush fluid (with old brake pads still inside) THEN after flushing and topping up with new clean fluid do I replace with new brake pads?

    2. Have I missed any steps, are there any suggestions? should I be careful with anything? Any advice is extremely helpful
  2. I would suggest that you change the fluid BEFORE you replace the pads, that way if your messy and spill fluid all over the place your not going to ruin the new pads.
    • Like Like x 2
  3. I would be very careful of operating brake lever/pedal with pads out. This will force pistons and if they come out too far you may have problems .

    I wouldn't be sucking out the old fluid as first step of a fluid change. Top the fluid up and then carefully operate brake to flush through. Repeat ensuring you don't let the fluid get below the minimum inspection level until the fluid coming out is fresh. Different coloured brake fluid assists. Doing it this way means you wont let air into the lines eliminating or at least reducing the bleeding procedure.

    Technically it shouldn't matter if you change fluid first or pads first. However I'd be inclined to do fluid first so if you stuff up and get fluid everywhere it won't be on the new pads.
  4. #4 Harb, Jan 8, 2016
    Last edited: Jan 8, 2016
    Pretty much spot on with the brake pad change. No need to open the fluid reservoir during the change, but it would be a good idea to do so anyway while pushing the pistons back in. Keep in mind how the little metal clip which puts tension on the pads sits on the caliper. Rags and toothbrush are fine on the piston, brake cleaner is fine to use around it. You may need something stronger to get rid of the old grit though - I've never had an issue with warm soapy water followed by brake cleaner to dry it all off. If you don't have a safe way to push the pistons back in, place the old rubbish pads in and push against them via preferred leverage method. I usually use a large pair of multigrips and enough cushioning to guarantee a clean job without any marks.

    For the fluid, you can remove the majority (making sure the fluid is never much below the minimum mark, this could lead to stubborn air bubbles which need to be bled out) by using a tissue to soak what's in the reservoir if this is easier for you. Pump the lever and keep firm pressure while opening the nipple, letting the lever slowly hit the bar, then closing the nipple before relieving pressure - or just use your vacuum kit. Keep doing it until fresh brake fluid is going out the hose and keep the fluid topped up above the minimum mark. Cover everything good as some reservoirs like to splash about a bit and brake fluid isn't too nice on paint and plastic.

    When opening the reservoir, find a good fitting phillips head, and give the screwdriver a couple solid taps to seat it in the screw before turning. When tightening, don't do it too tight - it'll seal well and won't go anywhere if done up reasonably. Be sure to place the plastic and rubber sealers under the reservoir cap the same as before. The rubber should be flat (it changes to account for the change in pressure as the pistons eject), not pyramid shaped with new pads. Keep the brake fluid with the new pads just high enough to see a small air bubble at the top of the master cylinder view hole when the bike is off the stand - this is so you can check the fluid before or while riding. The fluid will drop as the pad wears and is a good indication of how much pad material you have left.

    Pads before or after is your preference.

    Edit: Oh.. and follow caliper installation to a T - loctite as required, torque it accurately, make sure you do up the bolts reasonably evenly. And as you said be sure the pads are biting before you start rolling. Nothing like pushing the fronts having them go straight to the bar because you forgot to pump them to wake you up.
  5. Hey bud, thanks for replying. Given I am using a vacuum flush thing, is there any need to even pump the hand break lever?
  6. Sometimes you have to pump it a few times depending on the design of the braking system as some will only let so much fluid past. Normally the back brake is the stubborn one.
  7. Usually no need to use the lever if using a vacuum pump.

    Another little tip - poke a small hole in the brake fluid container rather than take off the whole seal. No mess, just squeeze the bottle to decide how much you want to place into the reservoir. Remember that brake fluid is hygroscopic (absorbs water from the atmosphere) and water greatly reduces it's boiling point. Feel free to use the whole bottle of brake fluid if you won't be using it in the near future - it doesn't have a long shelf life after the seal is broken.
  8. It's air that you don't want in the brake line. HarbHarb is right, but use kitchen towel as opposed to toilet tissue! I also use a clean cotton bud to remove any crap in the reservoir. Also use a thin cable tie to secure the vacuum tube to the brake nipple to stop it pinging off and flinging fluid everywhere.
    If you use the vacuum pump method and get loads of air bubbles coming through it'll mean you've undone the nipple too far and it's air from outside rushing through - not air from the brake pipes / calipers. You'll get through heaps of fluid for no result if you keep doing it.
    Personally i prefer the manual method with a mate to help out, and fluid first, pads second.
  9. Thanks for all of your replies/advice. So here is how it went (lol). The flushing from the reservoir was smooth and fine. Fluid was pretty dark compared to the new fluid. Flushed that out, cleaned the reservoir which wasnt actually too dirty. Went to the front wheel caliper opened the nipple and dealt with that. Lots of bubbles came through (think i'll use the zip tie next time). But anyway flushed it all out and that was fine. Continued topping up the reservoir. Did this about 3 times to make sure all the old fluid had drained out. So front caliper and reservoir were both fine.

    I changed the brake pads on the front caliper fine but me being me and thinking I was a pro at what I was doing accidentally located the wrong bolt (to remove the caliper from the disk) and unscrewed the brake line bolt and brake fluid came out. Luckily i didnt unscew it that much so it didnt go EVERYWHERE just a bit over the caliper and I cleaned that off with brake cleaner. Anyway, located the correct 2 bolts and change those brake pads fine. Put everything back together, pumped the front brake lever a few times and the brakes were EXCELLENT. Actually a bit too much braking power :) Oh i cleaned the pistons as well.

    Rear reservoir was disgusting. I flushed that out and topped up with new fluid. I however couldnt flush it through out of the rear caliper nipple because the screw to open the nipple was FAR too tight so i am waiting to get the exact tool to unscrew that. Also, i took off the caliper and the brake pads were basically dust so luckily i was going to change them. Issue is that the piston was slightly out and with the worn in old pads, everything fit. With the brand new pads, they wouldnt fit over the disk and i didnt have the strength to push the piston back in.. SO I ended up putting one new brake pad and one old brake pad (that fit over the disk). I now have the tools to open the nipple and push the piston back in. Maybe once I open the nipple, the piston may go back in without too much pressure? Not sure but planning to do that tonight and get it all done with.

    I have been riding twice since I did that Saturday arvo and everything is OK for now.. but I really need to fix the rear caliper (fluid flush) and put in the new brake pad. Took me HOURS because to remove the caliper on the rear, one of the bolts is really close to the exhaust (CBR250R) so I had to kind of take off the exhaust to get a good reach of the bolt. Anyway, glad I did it. You live and you learn!
    • Winner Winner x 1
  10. Oh and used Motul Brake Fluid and Ferodo brake pads (supplied by the dealership).
  11. I usually use either a clamp or a proper tool to push Pistons back in.
  12. #12 robsalvv, Jan 11, 2016
    Last edited: Jan 11, 2016
    I think I have a post about brake pads and their care around here.

    I don't have a vacuum thing, but do use a bleeder hose with one way valve. Fit hose over bleeder nipple. Build up pressure in system. Crack open bleeder watch fluid flow into bottle. Top up reservoir as required. Repeat. I've also do the careful piston extension job with brake cleaner and a tooth brush... keep close tabs on the amount of extension!

    Another thing about brake pads, some sites recommend roughing them up by scrubbing a few figure 8's on a concrete surface to break the manufacturing glaze and others talk about "bedding" them down by a stepped increasing braking application process on the bike in a quiet street to gradually get the temperature up to finish off the curing process. I do both. Don't know if either is necessary.

    +1 on ensuring caliper bolts are correctly tightened.
  13. I just went up and down my parking lot slow and fast and applied the front AND back together and everything seemed ok. Then went out for a ride around my streets and it was fine.. so far so good :) thanks for everyone's input. You are all amazing!!!
  14. Well I certainly am. Not so sure about everyone else
    • Like Like x 1
    • Funny Funny x 1
  15. Thanks for this post. I plan on servicing my cbr250r brakes this week and this post will help alot. Thanks again