I took the master cylinder and rebuilt it. Bench bled the MC and attached to the bike. The fluid in the brake lines was actually pretty clean but someone left the bleeders open so there is very little to no brake fluid in the calipers and anti-dive. I'm kinda stumped at this point. I tried to bleed the brakes as I would normally do. Staring with the furthest away (left side caliper) and not really building pressure although I'm getting some fluid out the bleeder.
My question is what is the proper sequence to bleed the front brakes with anti-dive still attached? I do have a Miti-Vac but rarely use it. I'm old school.
Your sequence is correct, start with the furthest.
I use my Mity Vac all the time, if you have it, why not?
If you have a large syringe you could try reverse bleeding. Just be careful about fluid coming out the reservoir.
DOT 3/4 does not play well with paint and plastics.
thank you for confirming my sequence. Actually I use a combination of Mighty Vac and pump pump hold for the final bleed. Just never seem to get brakes bled with just the Vac. I'm probably not using it correctly.
I've had to re-prime the lines two times since owning my 84 and all I can say is it is a dark art. If the calipers are dry after rebuild, it is extremely difficult to get all the air out of them. The second time this happened (the first time I gave up and rode the bike sans front brakes to a bike shop) I bought a brake bleeder kit and used that. But even after pulling a bottle of brake fluid through the system there was no pressure at the brake lever. I then tried a "trick" someone recommended on this forum - tie the brake lever fully compressed against the grip overnight - and it will correct itself. The next day- at least partially - I had brake pressure. It required the lever to be pulled almost all the way to the grip to fully compress. I adjusted the brake lever screw to add more leverage and over time the system corrected itself fully and I had to let out the adjustment screw to release some leverage from the brake lever. This was the same situation I ran into the first time when the bike shop did their work. I believe the problem is that the bleeder valve isn't positioned such that all the air can be expelled from the caliper. But you can get it to a point where they will work. From there you have to use the brakes/wait till all the air in the system eventually finds its way out. As for the "trick" - I'm not convinced that the same thing would not have happened by allowing time to let air bubbles to work themselves out of the system. Like I say, it's a dark art.
If you guys think the front brakes with the anti dive is hard to bleed, try bleeding the FJ with ABS lines.
Jeeze, that was a chore.
Tying back the brake or clutch lever and leaving it for any time does nothing.
There is a small hole in the bottom of the MC. When the piston is fully retracted, the reservoir is connected to the brake line thru the small hole. If the piston is advanced (lever squeezed) about 1/8-inch, the piston seal moves past this hole and completely blocks off the reservoir from the brake line. (If it didn't, then you would never build any pressure in the line; it would just go right back to the reservoir.) So there is no way that air in the lines can escape into the reservoir with the lever pulled.
What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir. You could have accomplished the same thing by walking away and drinking a cold beer.
Bill
Front brakes are bled and now onto the rear.
FYI I started with the left side Anti-dive then the left side caliper. Then right side AD and then caliper. I got tires of sucking fluid and air out last night so I used a large-ish rubber band to tie the lever back overnight. I've done that often over the years, I think the problem lies in that the VAc can't pull the fluid through fast enough to get all of the air in the lines. That is why some folks reverse bleed them with a large hypo. Probably just loosening the banjo bolt at the MC would work quicker for expelling the air in the lines. I have never tried that and quite frankly I'd be afraid to expose the brake fluid to air for that long if leaving it overnight,
The mighty-vac does a good job if all you are doing is the routine flushing or trying to bleed the caliper with the brake lines full of fluid. Starting with everything bone dry is a challenge to be sure.
So in summary? I did all 3 things. I bench bled the MC first. Then I tried to pump pump hold then onto the vacuum pump then tied the lever back for overnight. This morning a few pump pump hold and brakes are firm as they can be. I used the same sequence stated above starting furthest away and working my way back.
When I revive a barn find I don't even evaluate the brakes. Every thing comes off for cleaning/rebuild so I'm used to dealing with a dry system. It just takes a while. My OP asked for the recommended sequence and thank you for that.
FYI at least the rear brake system looks it came from a period Suzuki! One tip. If you don't have a rebuild kit, with internal O-rings, don't split the rear caliper.
Quote from: CutterBill on June 27, 2017, 07:51:49 PM
Tying back the brake or clutch lever and leaving it for any time does nothing.
What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir. You could have accomplished the same thing by walking away and drinking a cold beer.
Bill
Au contraire Bill,
For reasons I have not been able to determine, understand or figure out yet...
Tying the handle back against the bar even for a couple of hours does work and work very well.
There have been times we have bled a quart of fluid through a M/C and cannot get a perfectly solid handle. The first time I tried it out of speculation after reading it on this forum many times. I tied it back and went home, the next morning I cut the zip tie off not expecting any change. Much to my surprise it worked.
We now tie the handle bar and leave it for at least a few hours on all master cylinder bleeds. We do the basic bleed whether reverse syringe bleed, gravity bleed or pump bleed then we tie back the handle. Each and every time you untie the lever the lever is perfectly solid.
I know the holes in the motorcycle M/C are microscopic, especially when compared to automotive cylinders. I am not sure if the clamping allows all of the tiny bubbles to converge into one large bubble. Or if since the intake port is so small, the larger volume of fluid allowed in while compressed allows the fluid to flow properly through the compression chamber once untied...
I do not know why or how it works, but...
I do know it does work.
Randy - RPM
FWIW, you can replace the banjo bolt at the MC with a banjo bolt that has a brake bleeder built in.
This little mod will be just the ticket for bleeding air from the highest part of the brake lines.
Quote from: red on June 28, 2017, 05:27:01 PM
FWIW, you can replace the banjo bolt at the MC with a banjo bolt that has a brake bleeder built in.
This little mod will be just the ticket for bleeding air from the highest part of the brake lines.
Or do what I always do. Pump the MC a time or two and crack the bolt loose and watch for air bubbles. Usually only takes one or two iterations of that to free the air trapped in the banjo bolt. If there are no bubbles it will squirt fluid out pretty voraciously. Covering the bike with plastic and towels keeps the painted surfaces unscathed.
Quote from: racerrad8 on June 28, 2017, 11:18:10 AM
Quote from: CutterBill on June 27, 2017, 07:51:49 PM
Tying back the brake or clutch lever and leaving it for any time does nothing.
What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir. You could have accomplished the same thing by walking away and drinking a cold beer.
Bill
Au contraire Bill,
For reasons I have not been able to determine, understand or figure out yet...
Tying the handle back against the bar even for a couple of hours does work and work very well.
There have been times we have bled a quart of fluid through a M/C and cannot get a perfectly solid handle. The first time I tried it out of speculation after reading it on this forum many times. I tied it back and went home, the next morning I cut the zip tie off not expecting any change. Much to my surprise it worked.
We now tie the handle bar and leave it for at least a few hours on all master cylinder bleeds. We do the basic bleed whether reverse syringe bleed, gravity bleed or pump bleed then we tie back the handle. Each and every time you untie the lever the lever is perfectly solid.
I know the holes in the motorcycle M/C are microscopic, especially when compared to automotive cylinders. I am not sure if the clamping allows all of the tiny bubbles to converge into one large bubble. Or if since the intake port is so small, the larger volume of fluid allowed in while compressed allows the fluid to flow properly through the compression chamber once untied...
I do not know why or how it works, but...
I do know it does work.
Randy - RPM
As I mentioned earlier. I think the vacuum bleeder won't pull fluid through quick enough to get any air trapped in the TEE fitting or higher up in the line. Tying the lever back opens the MC for flow in both directions so the air will eventually work it's way up through the fluid and out into the air gap above the fluid level in the reservoir. If you have clear tubing on your vacuum bleeder you will notice that the air bubbles actually move pretty slowly in the fluid.
Like you, Randy, I always tie the lever back for a few hours or overnight even when I think I have a good bleed. I am new to this forum but not new to forums or wrenching on motorcycles. I've revived almost 30 of my own bikes and I don't know how many customers bikes over the years. If there were an easier way to bleed a dry system, I'd know about it....LOL :good2:
For the sake of scientific research, the next time someone decides to "tie the lever back and wait overnight," please skip the "tie the lever back" part and just leave it overnight and see if you get the same results.
I'm betting the outcome will be the same.
DavidR.
Quote from: FJ_Hooligan on June 28, 2017, 08:46:28 PM
For the sake of scientific research, the next time someone decides to "tie the lever back and wait overnight," please skip the "tie the lever back" part and just leave it overnight and see if you get the same results.
I'm betting the outcome will be the same.
DavidR.
BTDT...
That is why I finally tried the tie back method after being unable to get I solid lever.
Now, I do it each and every time with great success.
Randy - RPM
What? No video?
Just kidding Randy.
I'll have to believe you since I've never had to do this. I've bled ABS and non ABS brakes, and clutch systems without even using a MitiVac. I've had good success with just taking my time and letting the bubbles rise up to the master cylinder.
DavidR.
Quote from: FJ_Hooligan on June 28, 2017, 09:23:08 PM
What? No video?
DavidR.
That is not a bad idea. I can show the lever pulling all the way back to the grip. Let it sit over night, then cut the ties and the next pull does not go to the grip.
I will have to remember to do that on the next one we bleed.
Randy - RPM
With regards to "scientific research" will we get the full unedited version of the tying back and release of the lever video?
Will you leave a light on the lever overnight so we can watch and wait patiently for the outcome (popcorn) (popcorn) (popcorn) (popcorn) (popcorn)
Cheers Alan
got the rear brake cleaned and bled. I had one little snag that had me stumped for a while. The piston in the rear MC was frozen solid. I tried hitting with a punch but decided that it was in all the way and not budging. So I got the idea of using my bench front MC, that I have bolted to a piece of handle bar and clamped in my vise, to push the piston out. I just hooked the output of my bench MC to the output of the rear MC and pumped it. Easy as can be the piston started moving and finally popped out. I also must mention that I had plugged the reservoir hose with a bolt and hose clamp. That was to force all of the fluid and pressure to work against the stuck piston and not go spraying all over the shop. Since I had already put my Mighty-Vac away I did the old school pump pump hold routine. Within a couple of minutes I had the rear brake bled and working perfectly with a rock hard brake pedal.
I don't know if you guys normally just remove the rear MC from the frame or not. I decided to remove the whole frame assembly and I'm glad I did. I was then able to clean all of the moving parts, confirm the brake light switch worked and clean the connectors. But most importantly I was able to pull the brake lever pivot out, clean, re-lube, and install. If you do it this way be sure and have a foot pound torque wrench as that swing arm nut has to be torqued to 65 foot pounds. Also that cotter pin on the linkage would have been an absolute nightmare to get out and put back in with the side frame still attached. Actually I'm not sure there is enough room to remove that clevis pin with the assembly still attached to the bike.
How master cylinders work...
https://www.youtube.com/watch?v=SFbt46mN2k8 (https://www.youtube.com/watch?v=SFbt46mN2k8)
Pay close attention to the piston, the primary seal and the compensating port. You can see that when the piston is depressed, there is NO connection between the reservoir and the fluid ahead of the piston. There is no way for air in the line to escape to the reservoir.
Just as a single data point, last month I disassembled and rebuilt the clutch, front and rear brake systems on my '93. I did this to fix the stuck caliper pistons and because I was switching over the DOT 5 fluid and wanted to clean the parts. So I was starting with completely dry systems. Now, I don't know what people are doing when they say that they have so much trouble bleeding their clutch or brakes, but it took me about 30 minutes, start to finish, to do all three systems. Working alone. Didn't have any trouble.
But then, I've been doing this a while...
Bill
Quote from: CutterBill on July 01, 2017, 11:58:56 PM
How master cylinders work...
https://www.youtube.com/watch?v=SFbt46mN2k8 (https://www.youtube.com/watch?v=SFbt46mN2k8)
Here's a couple about tying the lever back.
https://youtu.be/ex-evh2g1O0?t=5m28s (https://youtu.be/ex-evh2g1O0?t=5m28s)
https://youtu.be/MQtT3XpB_B0 (https://youtu.be/MQtT3XpB_B0)
https://youtu.be/m4wlSQDsEHw?t=5m34s (https://youtu.be/m4wlSQDsEHw?t=5m34s)
LIke I said before...
Quote from: racerrad8 on June 28, 2017, 11:18:10 AM
For reasons I have not been able to determine, understand or figure out yet...
I am not sure why it works, but it does.
But then, I've been doing this a while
too...
Randy - RPM
Just some thoughts on what happens when holding the lever back to bleed the brakes/clutch. More so on the brake than clutch but the compression will only affect air trapped in the system. The air bubble is compressed into a smaller bubble. This reduces its over all size, Also reducing its surface area. This reduced surface area makes it easier to break free, float up, where it can escape into the port back into the master reservoir. i don't have a dog in this fight, my last experience with the clutch was bled with a few strokes of the lever.
Markus, I think you're on to something. :good2:
I've often wondered about that...If brake fluid under pressure affects the gravity movement of air bubbles.
I didn't think of compression affecting the actual size of the bubbles.
Makes sense to me: Compression = Smaller bubble size = less surface area of the bubble to adhere, easier for the smaller bubbles to move up to closed bleed port.
We all agree that with the lever squeezed the bleed port is closed, correct? No bubbles can enter the reservoir...that was Bill's point.
However, relaxing the lever opens the bleed port allows the accumulated bubbles into the reservoir.
One of Murphy's Laws of Combat is: If it's stupid, but it works, it ain't stupid. Old school, Mity-vac, reverse syringe, they all work. Tying the lever back certainly doesn't hurt, so why not try it?
Hell, I even used a palm sander, minus paper, to vibrate the bubbles up and out of the system.
Quote from: FJmonkey on July 02, 2017, 01:03:15 PM
Just some thoughts on what happens when holding the lever back to bleed the brakes/clutch. More so on the brake than clutch but the compression will only affect air trapped in the system. The air bubble is compressed into a smaller bubble. This reduces its over all size, Also reducing its surface area. This reduced surface area makes it easier to break free, float up, where it can escape into the port back into the master reservoir. i don't have a dog in this fight, my last experience with the clutch was bled with a few strokes of the lever.
I'll buy into that!
DavidR.
This was covered way back too. I recall this post and thought to myself it would not work back then.
It should be bleeding obvious (http://www.fjowners.com/index.php?topic=9548.0)
But, once I tried it I use it almost every time.
Randy - RPM
There is a lot I don't know. But I've been buying old non-running bikes for a few years, fixing them up and flipping them. I have one major rule. I won't sell it until it runs well enough and is safe enough to put one of my sons on it for a cross country ride.
The compressed bubbles theory is what I've always thought as to why it works. It shouldn't work but it does. Kinda like engineers and scientists absolutely proved that a bumble bee can't fly. But for some reason they can fly.
I also try not to over think things. If it works, I don't really care why. For the past 11 years I've been tying the lever back, or weighting the brake lever down overnight. If the brakes aren't rock hard in the morning I know I missed something.
My new to me FJ1100 had a bone dry clutch system when I brought it home. I was in a hurry and mad as can be that the PO broke one of the slave mounting bolts. So after I bled the system a bit I decided to quit and finish up the next day. I got a largish rubber band and tied the clutch lever back. The next morning I had full clutch action and no more bleeding necessary.
Long story short. It can't work. It shouldn't work. There is no way it works. But it does.
Quote from: jdvorchak on July 04, 2017, 07:03:42 PM
The compressed bubbles theory is what I've always thought as to why it works.
A few lines from an old post on this subject (in this case, specifically about the clutch):
"
It is a basic fact of fluid dynamics that with any bubble in any liquid, the smaller the bubble the more slowly it rises."
"While smaller (compressed) bubbles have less surface area and less friction, the fluid density remains constant and the smaller ones have less buoyancy."
"In the case of the FJ clutch, the route from the slave to the M/C is all uphill and the air will naturally want to rise to the top anyway, but slowly. IMO all the tied lever overnight does is inadvertently allow time for this process to occur naturally. "
Noel