Bleeding new brake master cylinder

[QWKDTSN]

I have never done this before so I am kind of curious... I just bled out my new rear brakes, kind of spongy, so I will go ahead and install a rebuilt 15/16 master cylinder in preparation for new front brakes. I am just thinking, when I remove the brake lines from the cylinder and remove it, then install the new cylinder, won't there be air bubbles in there? And if I fill up the new cylinder won't there be bubbles trapped in the lines? Is there any way to get around this? Tap everything and hope the bubbles make their way to the surface, or do I have to bleed them all the way down the lines and out through the calipers? Is it just a question of bleeding the master cylinder properly?

[Guest greimann]

Once you break the lines at the master cylinder, all the calipers must be bled, starting from the one furthest away from the master and ending with the one closest. No shortcuts on this. These are your brakes!

[Kevin Shasteen]

I dont know about the newer Z's but the older Z's master cylinders have an equalizer valve in them, so if one resovoir gets low it will allow the full resovoir to spill over to the resovoir with low level fluid. So dont just fill up one resovoir & think you have it taken care of. Make sure you always check & fill both resovoirs at the same time.

 

When you are ready to bleed the brakes, and if you dont have a one person bleeder, get a friend to pump the brakes up three times and then have them hold the brake pedal down on that third time; then turn the bleeder valve on the rear passenger brake till it opens and the air trickles out...sometimes air bubbles will sputter out with the fluid. So, look for a bubbles in the fluid. Once the pressure in that valve is relieved, tighten that valve (softly=but snugly-you dont want to strip their threads).

 

Repeat that procedure once more on the same brake. Always have your friend pump the brake pedal three times and hold them down on the third time-then while your friend is holding down on the brake pedal-open the bleeder vavle. Always do this twice per brake.

 

Then move to the rear driver's brake & do the same thing. Thirdly, move to the front passenger brake & repeat the procedure. Fourthly, move to the front driver's brake & do the same thing.

 

Next, check the level of the fluid in both master cylinder resovoirs; fill them up if needed.

 

Now repeat the brake bleeding process once more checking the master cylinder often. You may have to do this entire procedure three times, and you may have to do it seven times; it all just depends on how quickly the air bubbles move thru your system....you can tell when you are done as when the bleeder valve is opened you see nothing but fluid and your brake pedal should be solid.

 

If you dont have 4wheel disk brakes...you need to make sure your rear brakes are adjusted correctly. If you have rear drum brakes & they are too lose; you will never get that solid brake pedal feeling.

 

That is pretty much it. If you find yourself constantly having to refill you master cylinder over the next week or every few days, then either a bleeder line is not fully closed, a leaky wheel cylinder or a leaky brake fluid line at one of the brake line connections.

 

Hope that helped you; dont let it get you too uptight as it really is pretty much a straight forward process....it either is a tightly sealed system and your brake pedal is solid or you have a leak somewhere & the pedal is not solid; and or air bubbles are still in the lines.

 

Kevin,

(Yea,Still an Inliner)

[pparaska]

Sometimes there is air trapped in the last few mm of travel of the MC that you can't get to if it's mounted in the car. This goes for brake or clutch MC. That's why it's very important to BENCH bleed the MC before installing it. Run tubes from the outputs of the MC to the resevoir and keep pumping with the full throw until the bubbles stop.

[Miles]

Pete

 

Would it be possible to get those last remaining bubbles of air out of the MC using a vacume type bleeder?

[260DET]

All the above, plus if you can't get a helper, use a suitable length piece of wood to apply pressure to the pedal once you have pumped it a few times. Rest the back of the stick against the X member under the front of the seat.

 

Plus, after the initial bleed and if the pedal is not solid, come back next day and bleed again, just a couple of bleeds at each point. This usually gets a few bubbles of air out and can make the difference between a reasonable pedal and a solid one.

[pparaska]

I dunno. I guess a vacuum bleeder might do it.

[Pop N Wood]

I use to need a helper to bleed brakes, doing pretty much what Kevin said. But a many years ago I decided to connect a piece of clear tubing to the bleeder valve and to run it into a jar with an inch or two of brake fluid in it. This allows you (by yourself) to pump the brake pedal at will without stopping or closing the bleed valve between strokes (putting the tubing in fluid prevents the air from being sucked back into the calipers on the back stroke). Just remember to keep the MC reservoirs full and to close the bleed valve before disconnecting the tubing.

 

This has worked so well for me through the years that I always wonder why anybody makes or buys the vacuum bleeder kits. It is also a no mess way to cycle a lot of brake fluid through the system to flush it. Any dirt or air is clearly seen in the tubing, just keep pumping until it is gone.

[pparaska]

Jim, I've used that method too. One thing to watch for is leaks around the threads of the bleeder valve. This will let air back into the system when the pedal goes up. Sometimes int helps to put some pipe sealant (paste type) on the threads of the bleeder valve to help seal the valve threads.

 

I'm getting ready to bleed my hydraulic clutch TO bearing tonight, and I'm going to try using the power flush system. Fill the reswvoir to the top. Take a bike inner tube and cut the area around the valve out so that you can seal it around the resevoir (with the lid off) using a hose clamp. Apply 15 psi of air. Crack the bleed screw and let it out until the air comes out (watch that you don't run all the fluid out of the resevoir).

[Guest gprix1]

I like using Speedbleeders

http://www.speedbleeder.com

 

for a few bucks a wheel you can have a very easy way to bleed your brakes forever and wherever without any special tools. I put it on the clutch too.

 

#1 Before you start, if your changing master cylinders bench bleed it as pparaska suggested.

 

Here is my favorite method to bleed the system. It takes literally about 5 minutes to completely bleed the brakes but requires two people and three would be even better. I get my wife and my son to help with this.

 

You will need:

(1-2) 32 Fl. OZ (the large one) DOT 3&4 brake fluid. I recommend Valvoline Synpower Synthetic (in the gold bottle).

 

Speedbleeders installed on all four calipers

 

#1 Connect clear hose to the farthest brakes Speedbleeder so that it drains into a container.

 

#2 Crack the Speedbleeder open.

 

#3 What I like to do is get the fluid flowing out STEADY and FAST. This way the super-tiny bubbles (that foggy color) don't have a chance to come back up. Do this by pumping the pedal at a steady rate using the full pedal range.

 

#4 This method makes the fluid go down very fast so you MUST have someone standing over the resovoir adding fluid. This is why you need at least 2 people. If you stop to fill, you negate the benefits of a fast steady flow and risk sucking air.

 

#5 If you have a third person they can watch the fluid in the line and let you know when it looks crystal clear and with no foggy color; that's when you stop and close the Speedbleeder.

If you don't have a third person I would get 2 bottles of fluid and just bleed a little extra to be sure.

 

#6 Repeat 1-5 working you way closer to the M/C with each wheel. In 5 minutes, your done

 

Finally, brake fluid is attracted to water so take your garden hose and spray the areas that brake fluid may have come into contact with. Remember, leaving one drop of brake fluid on your paint can cause it to bubble, discolor, and/or flake off. It also promotes corrosion.

For those of you who like gadgets, here is a neat way to keep things clean with a bleeder bag:

http://www.speedbleeder.com/News.htm

[Owen]

What is the advantage of the Speed Bleeders? Do they NOT suck air back in when you release the brake pedal? What happens when you use these with pressure/vacuum bleeders? Are they just a waste of money if you have the Speed Bleeders?

 

Howz this thing?

http://www.motiveproducts.com/index.htm

Only $45 for the import model. Could probably be copied real easily too. My vacuum bleeder sucks, I always get bubbles from the threads of the shut off valve which confuses me with air in the system.

 

Owen

[Mike kZ]

I bought one of these.

http://www.phxsyss.com/phxinj.html

It pressure bleeds upward from the discs up to the master cylinder. This forces the bubbles up, the way they naturally go. Also excellent for the clutch master! Bleed the slave/master in a minute.