Brake bleeding issues
 

I just installed a new master cylinder and no matter how many times I bleed the brake lines on my '71 911E, the brakes are still useless......I am using the one way valve on a hose, then opening the bleeder valve and pumping the brakes, method. I pump about 30 times with no bubbles, then closing the valve, refill the reservoir, and do it again. I tried bleeding the master cylinder, too. I have bled them about 5 cycles per corner now, and they are still bad. If I pump the brakes about 30 times really fast after a bleed, then they start to get stiff, but loose the pressure the second I stop.

Can anyone help????:confused:

Either get a pressure bleedeer (Motive, as sold by our host, makes a nice one) or try doing it the old fashioned gravity method.

Fill your reservior with fluid.

Attach a clear hose to your bleeder screw and then open the bleeder screw.

Allow the fluid to slowly flow until no bubbles are seen.

BE SURE TO KEEP THE RESERVIOR AT LEAST 1/2 FULL.

Repeat for each caliper.

It sounds like you are trying to bleed the system by yourself. Traditionally, bleeding the brakes is a two-man operation. If you don't have a second man, a wife, a girlfriend, or even a sister will do. The best way I have found to do it by yourself is to use a vacuum pump (I'm talkiing about bleeding the brakes). I have a "Mighty-Vac." You put the Mighty-Vac hose on an open bleeder and suck the fluid through. Always start with the bleeder farthest away from the master cylinder. The only other thing that I have ever seen that works better is a pressure bleeder that pushes brake fluid through the system from the master cylinder end. Very messy but effective. Buy a vacuum bleeder.

Donald,

I used to do vacuum bleeding but always had problems of vacuum leaks at the bleeder screws. It worked but was a hassle.

About 2 years ago I when to a Motive bleeder and never looked back. To keep the mess down, I use only the fluid in the reservoir and use a tube to catch the bled fluid in a small container ( I use a graduated cylinder to know how much I bleed).

911eTarga,

You sound like you are doing it alone... get a buddy or save on the cost of beer and time and pony up to buy the Motive powerbleeder.

Brian

http://www.9magazine.com

http://www.oldwesttraveler.com

Motive make it so easy (I use it "dry" too)! Even if the system is empty of fluid as mine was when I replaced my m/c (without even a bench bleed) and installed 930 brakes. One time around and it was "good", and the second pass didn't even produce a single air bubble. All bleeds since then are even more painless...

Did you do any other work on the system? If so the calipers could be on the wrong side and the bleeders will not work, because they would not be at the highest point in the caliper. Another possibility is that there is a bubble "adhered" to the walls of the calipers. These bubbles can be released by hitting the caliper with a rubber mallet and then bleeding. I also purchased a power bleeder and it worked great.

Yup, bleeder valves need to be at the highest point on the caliper. There is a "right side" caliper and a "left stide" one.

Probably....your challenge has to do with not getting the MC bled. The workbench is the right place for bleeding a MC, but it can be done in the car. You might have to raise one end of the car or the other, to get the bubbles out of the MC. Disconnect the lines from the MC, one at a time. Hold your finger over the hole while someone pumps the pedal. Brake fluid will go everywhere. Place lots of plastic and rags. This is the method I use. Again, MC's can be tricky to bleed. My suspicion is that your still has a bubble.

Thanks guys!!!
I just noticed some thing while thying another bleed. When I pump the brakes after closing the valves, the fluid in the reservoir goes down as I pump, but when I let the brake pedal go, it fills back up. It seems like the master cylinder is letting the pressurized fluid back out. Is this normal, or is my new master cylinder shot?

you can make a 'power bleeder' for about $10 from a garden sprayer

Another vote for the Motive power bleeder. Best $45 you'll ever spend on your car. I can do a complete flush in an hour, including jacking, removing and replacing wheels and cleanup.