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Bleeding Brake - STUPID AIR Bubbles

rkiefer2

Well Known Member
I had to replace my pilot side brake line and decided it was a good time to replace all the brake fluid.

I followed the instructions in the MM and from Matco. Still have 1 or 2 stubborn bubbles coming out of the brake cylinders by the pedals. I pumped another 6-8oz through and that removed most, but still have 2-3 small bubbles in the lines.

Is this normal? Just need to pump more 5606 Hydraulic fluid through it? I've been extremely careful not to pump in any air while doing the bleeding process.
 
I think you guys are saying the same thing.. on my -4, it helps to unbolt the masters and hang them inverted to get the bubbles to move,, could that work on the -12?
 
If you can make sure your brake lines have a continuous slope to the reservoir it will be an easier task and better install. Avoid loops, its not a dishwasher
 
I did the exact thing, replaced the fluid with a higher flash point one. The bubbles would be all gone then the next day a few would show up. I easily solved it by breaking the fitting upstream of the bubble and pushing the air out. It requires fluid / pressure at the wheel cylinder, a two person job.
 
If you get one of these and a translucent extension hose you can tell if you’re pumping air and it allows for a one-person job. I probably have to run a good quart or more through mine to get most of the air out. Still see some very tiny bubbles but nothing larger. Pumping the brakes while bleeding helps too.
 

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The problem with the -12 is the brake lines under the dash are not going continuously uphill this gives the air a place to get “trapped”. Micro bubble are put into the fluid when you pressurize it. After setting they join to create a bubble that is visible.
 
Just do what I do - upgrade to stainless braided brake lines so you can't see the bubbles. :D

This is actually a good point though. If we were using aluminum tubing or braided lines everywhere and not plastic tubing, you'd have no idea that a bubble exists. You'd just fill the system.. and stop when no more air comes out of the system..
 
It can be done solo, fluid has to move faster than bubbles.

I did the exact thing, replaced the fluid with a higher flash point one. The bubbles would be all gone then the next day a few would show up. I easily solved it by breaking the fitting upstream of the bubble and pushing the air out. It requires fluid / pressure at the wheel cylinder, a two person job.

I use a $5 1 liter/quart garden sprayer, drill out the nozzle, insert some 1/4 poly tubing with some plastic compression fitting and use vinyl to connect to the bleeder. I use a second poly tube connected to the reservoir with a brass fitting to allow the poly tube to insert 1/2 way down. That leaves an air volume and does not over fill the reservoir. Two hands are required to open the bleeder and hold the tube on it. The other hand opens the pressure supply. Easy, then return excess to the container. (the sprayers will probably be $10 this spring. :eek:) What a way to ruin the party.

I confess that the tube will pop off the bleeder and I really hate the mess. I spent too much on a monster of an adapter from Spruce that is supposed to attach to the bleeder. Don't know if it will work, it has not been used it yet.
 
I use a $5 1 liter/quart garden sprayer, drill out the nozzle, insert some 1/4 poly tubing with some plastic compression fitting and use vinyl to connect to the bleeder. I use a second poly tube connected to the reservoir with a brass fitting to allow the poly tube to insert 1/2 way down. That leaves an air volume and does not over fill the reservoir. Two hands are required to open the bleeder and hold the tube on it. The other hand opens the pressure supply. Easy, then return excess to the container. (the sprayers will probably be $10 this spring. :eek:) What a way to ruin the party.

I confess that the tube will pop off the bleeder and I really hate the mess. I spent too much on a monster of an adapter from Spruce that is supposed to attach to the bleeder. Don't know if it will work, it has not been used it yet.

I have made the exact same setup except for one thing. I put a tire valve stem in the top of the pressurized sprayer and pressurize with an air compressor, you don’t need much pressure of you will pop the sprayer.

The reason for using a compressor instead of the built in pump is the air coming out of the hand pump goes through the brake fluid an makes micro-bubbles, see my previous post.
 
I made one from a speghetti sauce jar. Two holes in the lid. One gets a air hose fitting and I feed regulated air in with my compression tester. The other I epoxy in a 3003 alum stalk that goes to the bottom of the jar. The clear vynal tube that connects to the stalk (can't remember size, but I think 3/16 ID) stays on the bleeder nub without support up to 15 PSI. The clear tube allows you to get rid of all the air before attaching to the bleeder.

It makes for a hands free bleeding operation so I can shake the pedals to help get the air out of them.

Larry
 
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Just did ours last month. Bottom bleeding was counter intuitive to the way I’ve always bled brakes. The pump oil can the service manual recommends I found just not good enough. I shopped around and found a reverse bleed pump from NAPA auto. Worked great. No bubbles and brakes (most importantly) are stiff. Good luck.
Ps the Napa pump I got was about $60. Expensive but it saved me a lot of time and frustration. Best of luck
 
Just did ours last month. Bottom bleeding was counter intuitive to the way I’ve always bled brakes. The pump oil can the service manual recommends I found just not good enough. I shopped around and found a reverse bleed pump from NAPA auto. Worked great. No bubbles and brakes (most importantly) are stiff. Good luck.
Ps the Napa pump I got was about $60. Expensive but it saved me a lot of time and frustration. Best of luck

Is that the Vacuum-Operated Bleeder Kit they sell for $54.99 or so? The MityVac?
 
I would easily pay $60 for a system to bleed my brakes! I have been trying to get the bubbles out for 3 days with a gravity system. I am close, but not there yet.

Im going to order the MityVac to see if it will work.
 
I made a system like the one Larry made in post # 13.
Got nervous about pressurizing a glass jar and having it break.

Present version uses a 1 liter Nalgene bottle from a thrift store.
Air pressure is introduced through a rubber valve stem inserted in a hole in the cap.
The clear vinyl tube that feeds the bleeder is warmed in hot water and inserted into a slightly undersized hole in the cap. It seals in the undersized hole and goes to the bottom of the bottle.

Also, like Bill in post # 12, "I use a second poly tube connected to the reservoir with a brass fitting to allow the poly tube to insert 1/2 way down. That leaves an air volume and does not over fill the reservoir." Any overflow through that tube is caught in a separate bottle.
 
Using the Mityvac are you filling up top and pulling out thru caliper ??
Stan

No. Mity vac connected to reservoir. Tubing on bleed screw placed in jar of brake fluid. Draw a vacuum and let atmospheric pressure do the rest.

Pro-tip: fill tubing connected to bleed screw before drawing the vacuum.
 
No. Mity vac connected to reservoir. Tubing on bleed screw placed in jar of brake fluid. Draw a vacuum and let atmospheric pressure do the rest.

Pro-tip: fill tubing connected to bleed screw before drawing the vacuum.

Got it, will try my Mityvac next time.
Thanks, Stan
 
Tiny bubbles that you can't remove are probably not going to reduce your brake effectivity to the point a pedal bottoms out, how does your pedals feel?
 
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