Do I have a bad brake bleeder nipple?

Ugh. This is so frustrating! After rebuilding my M/C, putting new brakelines on, and rebuilding my brake calipers, I've run into the problem of replacing the brake fluid! What the heck?

I started with my MityVac, but I kept getting air in the fluid, so gave up. I chalked it up to having a poor seal over my bleeder nipple, but that was probably wrong.

So then I went to the manual way - fill up the MC, open the bleeder nipple on the calipers 1/3 turn (with clear drainage tube attached), pull the brake handle in, close the nipple, release the brake handle, and repeat. After moving a few ounces of brake fluid through, I'm still seeing some tiny air bubbles coming out with the fluid. And at one point, some fluid leaked out around my bleeder nipple during the process. Oh, and I'll mention this is a new nipple, and I put a small amount of threadsealer on it when I installed it.

So... could it be that the problem with air in the system lie in the bleeder nipple itself? That it's pulling in air around its threads? There appears to be no leaks around my banjo bolts, and I've kept the MC fluid covering the bottom. I see no other place air could be getting in.

Unless a member give me a better way to proceed, I'm going to reinstall the old bleeder nipple and give that one a try.

It's worth mentioning that this is the first time I'm doing this... so no doubt, there's significant human error involved! But gee, I thought I knew what I was doing.

It's finally a sunny day outside in Minnesota after an awful wet month of May, and I can't ride! Ugh!

 

When the bleeder is cracked there will be some air that leaks past the threads; it's unavoidable. Keep using the Mity-Vac, but pay no attention to the steady stream of tiny bubbles (those are from the bleeder fitting), just look for the larger bubbles from the brake lines.

The way bleed nipples seal is by pressing their angled face (at the bottom of the fitting) against the angled seat that is machined into the bottom of the threaded fitting hole. All that the threads do is pull the angled faces together. The threads are not airtight (and can't be). Don't use thread sealer on the bleeders; you can do a single wrap of teflon tape to cut down on the amount of air you see while bleeding with a vacuum tool. Thread sealer can make it very difficult to crack the bleeders open again, and may result in the rounding off of the bleeder "nut".

 

Thanks k-moe. Now, as I pull the fluid down through the lines with the Mity-vac, do I need to work the brake lever at all?

I guess I honestly don't know how the MC works - in other words, when fluid is pulled down through the tiny hole, versus the larger hole. I'm only guessing that the larger one is the "send" hole, and the tiny one the "return" hole.

 

I tried again this evening with the Mity-Vac, and in total, I've put 10 ounces of brake fluid through the lines without getting pressure (or no air bubbles) so obviously, something ain't right!

Again, I have no fluid leaks anywhere, and have always ensured that the drain holes in the MC stay covered. So, isn't it possible that I didn't reassemble my MC piston correctly? Would that cause my problem and my inability to get any pressure in my lines? Here's a picture of the old piston on the left, and my new one on the right. I mean, my seals are on there correctly, aren't they?!



Here's a close-up view of the new piston by itself, as I just yanked it out:



If this still doesn't work, I'll film it!

 

take that bleeder nipple out and you'll see a tiny hole on the beveled end.
wrap the threads with a few wraps of teflon tape but don't cover the tiny hole, screw it back in and the bubble problem should be gone. wrap it on turning the bleeder clockwise. when your done just tighten it down and leave the tape on it.
try flopping the wheel so a bubble in the wheel cyl would go towards the bleeder hole

 

One more suggestion. Go to your local farm/ hardware store. Get a large syringe (WalMart and True Value have one for measuring 2 stroke oil that works well if you have no farm store nearby), and a length of clear tubing that will fit over the end of the syringe, and fit snugly on the bleed nipple. Fill the syringe with brake fluid (leave the master cylinder empty) and pressure fill the system from the caliper end.

The air will tend to work it's way up (there are some "air traps" in the calipers that are the result of how the passages were drilled) into the master cylinder, and out of the system.

GO slowly. There is some risk of making quite the mess if you try to rush.


also......did you use all new crush washers when you put the lines on? Did you accidentally get one out of place? Just trying to eliminate all potential causes of air leaks.

 

Inspect the BORE of the Master Cylinder.

Pitting and accumulated Crud will nix any chance of Bleeding the System.

 

Yes Rick, I inspected the bore after I meticulously cleaned it and it was beautiful.

To answer K-moe's question, yes, I used all new crush washers when I installed the new brakelines, and all banjo bolts were torqued to factory specs. But I'm assuming that if air was getting in somewhere along the lines, I'd also be seeing a fluid leak at the same place.

What irritates me about the Mity-Vac system is that the attachments shown below do not seem to create a very good seal around that bleeder nipple:


As a result, I've been using a clear tube instead at the nipple end. Looking at the picture above though, I see that upon close inspection, the ends are somewhat different. I had better go back and make sure I was using the tightest one possible.

To me, I see the biggest "problem area" in the brake system to be the area directly behind the caliper piston. I assumed I was OK in shoving that piston all the way back when I reinstalled it - I have no idea how much volume of brake fluid exists between the caliper wall and the piston when in the relaxed or non-braking mode.

Not sure what to try next, so maybe I will try K-moe's idea of backfilling the system.

 

When you have the nipple closed do you have a firm lever? Any resistance at all? These can be a PIA to bleed.

 

Nope - I was never able to build up pressure in the lever. That's why, for whatever reason, I decided to take my MC apart again.

 

You gave up too soon. I went through this with both of my 550 Secas. I'll give you some more ideas when I get home (too much to type right now.)

 

The syringe method works well. Once you have the piston working you can also pump the fluid back into the syringe in case you feel there might still be air in the caliper.

 

OK, got a minute.

You just gave up too soon. Polock's advice about the proper way to wrap the bleed screw is right on; you absolutely need to do that. Especially if using a Mity-Vac.

I didn't use the Mity-Vac "coupling" I used one of the tube-to-tube thingies and put an appropriate sized piece of tubing directly on the bleeder nipple.

I have gotten the best results by using my Mity-Vac followed by old school hand-pumped bleeding.

Be sure the tiny hole in the bottom of one of the "false" drillways in the M/C is clear. Use a bristle from your parts cleaning brush to poke thru it.

Bleed the thing as best as you can; the blasted tiny bubbles will NOT stop. Make sure the M/C is full, put the cap back on and pull the lever to the bar, and wrap a bungee cord around it and go do something else until tomorrow.

When you get back to it, you should at least be able to bleed it functional. The only way to get it truly and completely bled is to do it again after a couple hundred miles and a few "heat cycles." You'll get a nice fat bubble, guaranteed.

My theory is that the rough machining in the caliper bore traps "microbubbles" in the grooves that simply need TIME to migrate together and be able to be bled out.

I've worked on countless hydraulic disc systems on many different makes of bikes over the years and have never had as much trouble bleeding brakes as with the '80s Yamahas. I had a couple back in the day that I put stainless lines on and went thru this back then too.

 

Many thanks Fitz. I'll follow your instructions to the letter and report back on my success.

Great to know that others have struggled with this, because while I've heard that bleeding brakes was often a pain, I didn't expect quite this much of a PITA.

Merci from Minnesota!

 

I fail to understand "The Syringe Method".

The Main Master Cylinder Hydraulic Seal is a ONE WAY Seal.
Fluid is NOT supposed to seep beyond the Main Hydraulic Seal at all.

Sometimes the BEST Method is the "Old tried and true".

Wrap the Bleeder with Teflon and open the Bleed Orifice.
Fabricate an AIR TIGHT Bleeding Hose.
(2 Inches of Rubber Vac Line <> Coupled to Clear Vinyl Hose.)

Submerge the Bleeding Hose in a Jar containing Brake Fluid.
(Weight the Hose to KEEP the end SUBMERGED.)

Build some pressure by Working the Brake Lever.
(Use an assistant)
When pressure develops, ... OPEN the Bleed Nipple
HOLD the Brake Lever and let the Caliper evacuate.
Close Bleeder.
Pump.
Repeat.

Brake Fluid should not RETREAT back into the Caliper.
The M/C should PUMP Fluid down the Line out the Bleeder.

I don't understand how it is possible to develop enough pressure using the Syringe to FORCE Fluid and Air UPWARDS.

The process relies on Fluid and Air being evacuated Down and Out.

Most PRESSURE TYPE Fluid Bleeders operate by connecting the Under-pressure volume of Brake Fluid, to be introduced to the system, through the M/C by employing a device that substitutes for the M/C Cover.

 

I followed BigFitz's advice, but still no-go. I let it gravity bleed for several days, actually, and did the Mity-Vac route, but I could never get a steady stream of fluid.

I wasn't suppose to leave the brake level pulled in during the bleed, was I? I didn't do that.

Then, the handle feel off the Mity-Vac. So, I was back to the manual method - open the nipple, pull in the brake lever, close the nipple, release the brake lever, and repeat. I moved a fair amount of fluid (maybe 4x my MC capacity), and it still is not under enough pressure. Currently, when the brake lever is pulled, the caliper piston will move the brake pad about half the way to the disk, but that's it.

So... any other input in troubleshooting? I did just PM a fellow local XJ member to see if a in-person visit might save me from giving up.

 

Do your self a favor, ...

Pull the Master Cylinder's Cover.
Remove the Rubber Gasket.
Squeeze the Brake Lever.

IF Brake Fluid shoots-up in a fountain-like stream ... looking like the Dancing Waters outside the Bellagio Hotel and Resort in Las Vegas ...

The Seals in the Master Cylinder are dead, shot, beat, cooked, Foo-bar!
All the Kings Horses and all the Kings Men,
Won't be able to develop Hydraulic Pressure again.

"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein

 

Well, this was all part of a complete overhaul of my brakes, so I had just rebuilt my MC with all new seals. However, YES, if hold the cover up and squeeze the brake, a small line of fluid will shoot up an inch or two - it's hard to know how high it would go because I'm holding the cover over it to avoid the fluid going everywhere!

So, it shouldn't be doing this at all? I need to replace these new piston seals?

 

No, if you pump the lever with the lid off you'll get a small geyser. Your M/C is likely fine, you haven't got it bled yet is all. Only 4X the reservoir capacity is nothing; you'll likely run a whole bottle of brake fluid through it in this process.

First off, pull the caliper over (to the outside) so the "fixed" pad is tight against the disc on the backside.

Then, bleed as you were. In the "leave it overnight" scenario, the lever should be left pulled, yes. I wrap a cloth bungee cord around it to keep a pull going.

 

OK - roger that I'll move a lot of fluid through this before it's all bled of air.

Sorry to ask again, but does the brake lever remain pulled in the whole time if I'm using the Mity-Vac route?