bleeding rear brakes

[tyler]

Well i have finally decided to pu my front brakes on and get them working. The problem has ben getting them bled right but i have been working on a plate that will go over the resivore and work the same way as the lid with the hole in it on my rear brakes. So here are the pictures. I started with an old brake pad off our car, the ended up having to add some metal cut weld and drill alot, so here are the results.

After some cutting, grinding and drilling.

After more cutting welding drilling and adding some more metal.

 

[yamarider]

If you use the traditional bleeding method (apply brake pedal with bleeder closed, pump, and open bleeder while pedal is applied) do you get anything out of it at all?

I don't know the history of this, was the current master cylinder on the bike or did you just buy that too? If it was on the bike, was there fluid in the system, was it dry, was the line connected or not? If it sat a while with no fluid in it the seals may have dried out, requiring the MC to be rebuilt.

May also be another leak in the system, i'm not positive that this idea will work but i'm thinking if you open the bleeder and apply air pressure to it, if there's a leak in the system you should see some fluid coming out along the line or at a fitting.

Do all the fittings have good/new copper washers? If in doubt, the auto parts stores usally sell a pack of different sizes of them for a buck or two, replace any that are missing or worn out.

 

[boston350]

haven't tried the traditional method since getting it working with the vac bleeder - I guess I could try that tomorrow and see if it makes a difference.
when I got the the quad it had the MC and reservoir and all the brake lines - just no rear brake caliper. it was sitting dry for an unknown amount of time. so bad seals would let the fluid through for the bleed process - but not create braking power, or leak externally? rebuild kit looks cheap enough.

I did try blowing air backwards previously, semi successful since it didn't seal well - and the system was dry.

good call, there was no washer on the other end of the line that attaches to the MC - I'll find some for that. the other line was connected with the hose-clamp thing.

about 4" of fresh snow today so I took it out for about 20 min, ran good but didn't get it out of 2nd gear as it would slide like crazy if I used much front brake.


thanks!

 

[boston350]

Ran by the shop and picked up a couple banjo washers for that brake line. installed them and started to do a traditional bleed, no change.
I put the vac on it and got it to pull the fluid through again, less air bubbles this time, and I could hear a whistle at the master cly.
switched back to the traditional method again and could now hear the whistle still - it was coming from the boot where the arm goes in. after a few strokes it was bubbling and dripping some fluid.
so the MC rebuild kit is on order.

 

[91warrior]

after reading this im glad i bought my MC rebuild kit before i put my MC back on since it has been off the warrior for 5 years opened. i hope you get it fixed up. let us know how the rebuild for the MC goes. it will be two more weeks till i get home to rebuild mine though, but the kit is home waiting

 

[boston350]

Indeed, should have the kit on Tuesday, so with any luck I'll know on Wednesday.

 

[boston350]

Ok, been out of town and away for awhile so just getting back to this. Got the master off, not much trouble. first surprise was when I pulled the boot off the rod. It was all packed full of rust and dirt. Got that cleaned out enough to release the circlip. the rod came out easily but the top/bore area is still rusty. from the manual, it appears the piston assembly/springs should pop out as well. I tossed the whole thing in the brake fluid bath to see if that would free it up any. will check in the morning - but can anyone tell me if the rest of it should come apart like I think.
The book does say to compress the piston with the rod when removing the circlip - the rod moved fine, but doesn't appear to move/compress anything in the piston area. So it might be frozen in place.

 

[91warrior]

try pushing on that piston to see if it moves at all. if it doesnt, then you will have some work ahead of you. soaking it like you are is a good idea, but not sure if brake fluid would be the best to get it loosened. what you could do is used some light compressed air and blow into the inlet port of the master cylinder to force the piston out, just make sure you have a big stack of paper towels or something very soft so when the piston comes flying out, it doesnt fly around. im assuming your master cylinder rebuild came with a new piston like mine did? if so, you will likely have to put the 2 piston seals on and that can be a pain, just make sure you have the lips of the seals facing the right way, if you dont, the master cylinder will not work.

on a side note, i just remembered that you tried bleeding this before and couldnt get it to bleed. what actually happened when you pushed on the brake lever? the spring for the lever would make it return, but if the piston was stuck, it would be stuck up inside the master cylinder which would be why you could not get it to bleed right. its hard to really tell exactly what its doing without actually being there. i just rebuilt mine this past weekend and i used the vacuum bleeding procedure like you had tried, and it worked great for me, only took maybe 5 minutes to get it completely bled. i hope some of this helps, im not good at explaining things. let us know what you come up with.

 

[boston350]

thanks for the info. if the brake fluid soak doesn't do the trick I'll try air pressure.
the repair kit did come with a new piston, so as long at the bore isn't junked up too bad I should be ok.
When it was on the bike I believe it was the spring on the brake peddle that was returning the peddle back, nothing inside the cylinder.
we'll see what happens today

 

[DeadLastRacing]

your takin info from a guy who doesn't even run a rear brake (91warrior), smooth. heheheheh

 

[91warrior]

as of this past weekend i have rear brakes again!!, got them working after 5 years. has a brand new caliper and rotor and rebuilt master cylinder, it was very weird riding with rear brakes, if i didnt think about it, i forgot they were there to even use it lol. hopefully this set up will last a long time. even got an extra set of ebc severe duty pads for back up.

 

[boston350]

Well I got the piston out, at the end of the day. soaking in brake fluid didn't do it. tipped it up filled the bore with rust-buster for a few hours, nothing. hit it with the torch for a few seconds, nothing. blasted it with air, didn't budge. tried to drive it in a little more, it did slide in maybe a 16th of an inch. I squirted wd40 in the back side and let that sit for a bit then tried air again. with the compressor on 180 I got it to slide about 1/2. I could then pound it back and hit it again, this time it popped all the way out. the bore looked fine so it should be good to go. I'll put it back together tomorrow and see what happens.

 

[91warrior]

thats good to hear, hopefully everything else goes good for you and you will have your brakes working good agian.

 

[boston350]

went to put the MC back together today, kinda disappointed with the low res b&w pic in the manual. when I dislodged the piston with air yesterday if flew across the garage and couldn't be found or referenced - just had the spring and primary cup. the book makes it look like the small end of the spring somehow attaches to the piston - figure that has to be wrong. i go the secondary cup over the piston - am I right that the narrow end goes toward the end? put the spring, cups and piston back in, little resistance getting the secondary into the bore, but the spring still have enough push to move it back and forth. at least until I seated it far enough to put the circlip in. at that point the spring was not kicking the piston back and it just stayed put - is that normal? I figured fluid pressure would move it when things were bled and ready. put it back together and filled the reservoir up. went to bleed the system with my vac bleeder, found it wasn't making vacuum... it would still suck enough to pull air from the system, so I did that for 20 min - but wasn't able to pull fluid. since the piston was still stuck up I couldn't do a traditional bleed either. I'll see if I can take that bleeder back and exchange it tomorrow and try again.

 

[91warrior]

yea if that spring was not returning the piston, something is wrong. when you assemble that, you should be able to push the piston in fairly easy and it should return very easy. if not, somethings not right. the small end of the spring does install on the end of the piston thats inserted first into the master cylinder. the big tapered end of the spring is the first thing to go into the master cylinder. both lip seals are installed so that they are also facing towards the spring. if i had my old pieces out with me, i would take pictures of it showing what i mean. but those seals do have to be facing the right way for it to work. also if the seals folded back when inserting the piston into the bore, then it also would not work. so just make sure the seals are on the piston right and the spring is on the piston and insert the assembly into the master cylinder making sure the seals dont fold back or anything.

 

[boston350]

that's what I was afraid of. was hoping since it was new that it was just a tight fit. Guess I'll pull it all off again. The wide end of all the cups are facing into the bore.
when you slipped the primary cup on did you do it the long way - over all the piston, or just pop it over the end?
I ran it all the way down, was a PITA hopefully that didn't mess anything up. I'll double check that nothing folded up in the process.
Thanks

 

[91warrior]

yea if the wide end of the cups are facing into the bore, you should have the seals installed correctly if im picturing everything right.. i believe i tried slipping primary seal over the entire piston but gave up on that because it was just a pain and was afraid of messing it up so i chance on stretching it more and just slipped it over the big part of the piston and that worked (everything was coated in brake fluid also.

 

[boston350]

Ok. I did find the original piston on the workbench today too, so it is put on the same way. not sure what caused it to stick up in there, I'll rip into it again tomorrow hopefully. I had everything soaking in brake fluid for an hour or so before hand too.

 

[boston350]

Wow, what a difference one little piece of rubber makes. pulled it apart again, took a lot more effort to get the piston out this time. looked at it and started kicking myself - after all that talk and planning - the secondary cup was facing the wrong way. I swear it flipped in there somehow. I corrected that, soaked them again and put it back together. this time the spring was able to move the piston back and forth fully, no hangups. I did compare the old parts to the new ones; the old spring was about 3/4 the length of the new one and the old secondary cup was almost flat compared to the flare of the new.
buttoned things back up, filled the reservoir, hooked up the vac bleeder and after just two pumps it was pulling fluid. then I noticed an odd squirting noise from the caliper and saw fluid leaking. stuck my head back there and pumped the brake by hand(great peddle feel) and saw fluid leaking out around the banjo bolt. tightened it and tried again, still leaking. I had gotten some fancy washers that had rubber washers in the middle, were supposed to be better. I pulled those off and put the originals back on, still leaking, but less. tried a little thread tape on the banjo, still leaking.
Hoping it's just the banjo and I can pick one up tomorrow and not an issue with the caliper/threads. at least I have sorta peddle and moved the problem down the line

 

[91warrior]

ahh thats great to hear. heres a quick trick. take a lighter and heat up those copper washers with the banjo bolt just slightly lose, and then when you think they are all nice and warm, tighten down the banjo. sometimes this will be enough to make those copper washer soft enough that when you tighten the banjo bolt, they will seal. dont use the ones with the rubber in them though if you try this, it would probably mess up the rubber. but just something to try, i never had to try it before (when i did my system i was lucky enough not to have any leaks) an old timer had told me that trick and it sounds good idea. just dont put a ton of heat to it obviously, just till you think those copper washers are a little softer.