No pedal after replacing Master Cylinder...Help Please Options

[ChrisFix]

I replaced my original leaking master cylinder today with an ATE 17mm unit...install went fine, all my connections were clean and removed easily...I struggled a bit with the reservoir lines, but they are in clean and not leaking...

After installing the MC, I pressure bleed the brakes from RR, LR, RF, LF...ran lots of clean fluid through, didn't have much air except for the LF.

I got in the car to check the pedal after the bleeding, and it just goes straight to the floor (like it did with the bad MC I just replaced).

I have no leaks at any of the wheel cylinders, and they all bleed easily (and with clean fluid...no rust or gunk).

What am I missing here...I could understand getting a soft pedal, as I may need to bleed several times...but I don't get why I have no pedal at all.

Help please!! I'm moving on Tuesday and need to move my car with me (and hate the thought of taking it to my new place on a tow truck).

Thanks!
Chris

[messix]

rebleed master

[ChrisFix]

rebleed master

I didn't bleed the master, just the wheel cylinders. How do you bleed the master?

[Dr. Roger]

keyword searched "bleeding brakes"

http://www.914world.com/bbs2/index.php?sho...leed+the+master

http://www.914world.com/bbs2/index.php?sho...leed+the+master

http://www.914world.com/bbs2/index.php?sho...leed+the+master

[ChrisFix]

keyword searched "bleeding brakes"

http://www.914world.com/bbs2/index.php?sho...leed+the+master

http://www.914world.com/bbs2/index.php?sho...leed+the+master

http://www.914world.com/bbs2/index.php?sho...leed+the+master

Thanks for the links...I did search first for "Bleeding Brakes" (as well as "Bleeding Master Cylinder") - got 20 pages of results and didn't see the answer among the many unrelated threads that pulled up...at 3:00AM on a hot and sweaty NC night, covered in dirt and brake fluid.

Edit - Just read the links - all of which I found last night before I posted, and they don't say how to bleed the master cylinder...which is why I asked. Thought this would be easy to find but I was wrong.

[pcar916]

Check the links, but... did you bench-bleed the master-c?

Generally:
1. Don't drain the lines downstream from the master cylinder, just suck out the fluid from the reservoir and remove the old cylinder
2. Then bench-bleed (fill) the master cylinder and block the openings with the plastic plugs that it came with before putting it in the car.
3. Make sure the feeder line and reservoir are full of fluid as well, before you attach it to the mc, or you're pushing an air bubble into the mc.
3. A pressure bleeder is best but in a pinch, pedal-work works fine for new mc's... generally bad for old ones.
4. Alternate brake fluid colors to make it evident when the fluid has completely replaced the old stuff. I alternate ATE Racing Blue stuff and Motul clear.

The rest is as you described in that order. If you have dual reservoirs in your calipers they have to be bled from the inside out per wheel.

Good luck!

[pcar916]

To be specific.

1. With the master cylinder in a vise on your bench, push the piston in and plug the outlet holes

2. Let the spring push the piston back out while continuously putting new fluid into the inlet fitting(s). Never letting air to be sucked into the inlet hole(s). This may take a couple of times to get it right.

3. Once the piston is all the way out, and the cylinder is completely full, plug all holes and install into the car per my previous post.

That should do it.

[ChrisFix]

To be specific.

1. With the master cylinder in a vise on your bench, push the piston in and plug the outlet holes

2. Let the spring push the piston back out while continuously putting new fluid into the inlet fitting(s). Never letting air to be sucked into the inlet hole(s). This may take a couple of times to get it right.

3. Once the piston is all the way out, and the cylinder is completely full, plug all holes and install into the car per my previous post.

That should do it.

Thanks for the specifics...but to answer your question, no, I didn't bench bleed it (didn't come with any plugs in the outlet holes either).

So now that it is installed, is there a way to bleed it? Loosening the outlet fitting while under pressure (I have a Motive pressure bleeder)? If so, what is the difference between the single line and the dual line fitting with the banjo connection?

I do have some brake pedal now - but very low.

[pcar916]

If you have an air cavity now you will still have one later, although it will eventually go away many ounces of brake fluid later. Do the bench process in the car instead.

No pressure bleeder yet.

With the reservoir upcapped, and assuming the reservoir and feed line are full and air-free...

First, put on some major eye protection

Completely remove the outlet lines and have someone gently depress the brake pedal to the floor. With the outlet holes blocked with something, cork, rubber or fingers ... something, tell your assistant to slowly let the pedal up. This will draw fluid out of the reservoir and into the MC just like it was on the bench. Do this until fluid comes out of the outlets solid when the pedal is depressed. Then,

Tell your assistant to hold the pedal halfway to the floor, which will seal off the inlet, and hook up the outlet lines again.

Let the pedal back up and pressure bleed the system like before.

That ought to get you some pedal if the MC is ok.

Good Luck

[Cap'n Krusty]

No plugs in the various holes? Ate brake hydraulic components ALWAYS come with plugs in ALL the holes. It's important to remember that you never allow the pedal to bottom out while bleeding the brake system. The Cap'n

[76-914]

No plugs in the various holes? Ate brake hydraulic components ALWAYS come with plugs in ALL the holes. It's important to remember that you never allow the pedal to bottom out while bleeding the brake system. The Cap'n

Cap, please clarify for my dumb azz. Is this to say never push the pedal completely to the floor when bleeding.

[pcar916]

Cap is correct with a couple of considerations...

With used (in use) master cylinders, your normal pedal travel keeps the bore "scraped" clean. At the end of that normal pedal travel though, corrosion can form on the bore which forms a rough surface. The more often you bleed the fluid, the less corrosion will form from the water the fluid attracts.

When the pedal is pushed to the end of the bore, like when you are bleeding it in the car, the rubber cups on the piston scrape through the rough bores beyond their normal travel which can damage the rubber. With a new MC that's not the case. There is though the matter of how far down the bore is machined. More on that below. For most of us this means That means two things really...

First, If possible always use a pressure-bleeder so you don't have to push the pedal in more than normal travel. And second, keep your fluid refreshed regularly so the corrosion is kept to a minimum both in the MS and the calipers.

As to the depth of the machining in the bore, I'd have to go take one apart in the shop and see if it's a machined surface to the very end. And I'd have to check to see if the pedal travel will let the piston bottom out and deform the rubber cup at the end.

Cap may remember those details better than I without opening one up. What do you think Cap?

[cwpeden]

Just a note. I havent seen mention of the resevoir having 2 chambers in it, front and rear.

The first time I bled my brakes I was unaware of this and 'bled' the front half of the res dry. After much head scratching and a bit of cussing my buddy who was helping me reminded me. (IMG:style_emoticons/default/rolleyes.gif)

Perhaps this may be a consideration.....

[pcar916]

Yep, that's a consideration. But only on the bench when you may have to fill both inlet fittings at the same time. When it's in the car like this one is now, the reservoir fills both at once.

[pcar916]

Sorry, forgot to add that this is true with the pressure-bleeder he's using. It keeps both filled.

[cwpeden]

The pressure bleeder fills the resevoir as your bleeding? Hmm, sounds like something I need.

[pcar916]

Yeah, it's the only way to go. Makes the job easier, less messy and much quicker.

You can do it by yourself and never again screw up a master cylinder up pumping the pedal. (IMG:style_emoticons/default/piratenanner.gif)

[Derek Seymour]

Did you make sure that the shaft that is connected to the brake pedal is actually inserted in the MC boot and presing on the MC piston? If not you can remedy the situation by removing the shaft at the pedal assembly, then align it in the MC boot hole and reconnect it to the pedal.
To get the correct pedal play adjust the shaft so that it is touching the MC piston but not apllying pressing force on it when the pedal is in the neutral position. You will have to do this by feel.

edit: oops didn't see that you are actually getting pedal now... so disregard I guess.