Brakes on my '71E

911Etarga · 07-01-2008, 04:14 PM

OK, I have bled my brakes about 6 times per caliper, took the master cylinder out again and bench bled it....and after all that, I pump the pedal about 20 times and it gets hard but then goes soft if I leave it for more than 5 seconds (um, the brakes....). If a caliper is frozen, what will that feel like? Will the pedal feel like it is bottoming out (get rock hard)? The pedal doesn't feel like it is traveling as far as it should.

I am almost ready to give in and let a pro do it....

Flieger · Flieger's Garage

Sounds like a leak somewhere. You do not see any fluid inside the wheel rims or on the ground after sitting a while? There are lines through the transmission tunnel that are hidden and can fail, filling the tunnel with fluid until it gets high enough to come out. Try putting pressure on the pedal with a secure but not overly firm clamp for a long period of time -10 minutes? and see if there is a leak.

my1st911 · my1st911's Garage

A frozen caliper will not drop down. Your master may be leaking, and that will slowly drop down. So will a line leaking or caliper leaking externally. Do you loose brake fluid. My guess would be your master needs rebuild, or by an already rebuilt one. That would be my professional opinion

djpateman · 07-01-2008, 04:38 PM

If all four wheels are off, then try a test. Pump up until the pedal is hard. Release the pedal and go around to each rotor, and spin it. If one rotor remains locked after the pedal is released, then it is possible one of the rubber brake lines has collapsed, and is acting as a one way valve. There may be bubbles trapped in that circuit.

Do you lose any fluid while pumping the pedal, but not bleeding the system?

Are you still getting any bubbles when you bleed?

911Etarga · 07-01-2008, 07:26 PM

Thanks guys!
The Master Cylinder is new, but I noticed a small leak from one of the connecting lines, so I tightened it, bled, and still mush. The calipers only leak from the nipple when I have it open, and a small amount. I will check the tunnel for a leak there.

When I pump the breaks, I can see the level of the fluid reservoir drop slightly, but when I release the pedal, it comes back up. It's like the Master is letting go of the fluid....

Flieger · Flieger's Garage

The fluid flows from the reservoir to the pistons in the calipers when you push the brake pedal. When you release, the fluid comes back into the fluid tank. You are experiencing proper fluid level changes.

911Etarga · 07-01-2008, 07:43 PM

Would a bubble do this to me? I have bled and bled and.....I pressure bled it(with a home made pressure bleeder) I have pumped, I have vaccumed...If there is a bubble how else can I get it out?
Should I prop the car up with all four wheels off (I was told that this is dangerous)and do another round of bleeding?

Flieger · Flieger's Garage

Did you try a rubber mallet hit to dislodge air bubbles in the caliper?

911Etarga · 07-01-2008, 07:55 PM

Yep.... Is this the tell tale sign of bubbles? build up the pressure, only to loose it the minute you let your foot off?

Flieger · Flieger's Garage

Yes, you used a mallet?

Bubbles can soften the pedal in the manner which you describe.

911Etarga · 08:27 PM

Yah, I tapped them, but I can't tell if the bubbles are coming from the nipple or from the system, so I let a bunch of bubbles out, but it didn't help....

Flieger · Flieger's Garage

I dont think there should be any bubbles at all...

SP2 · 07-01-2008, 10:21 PM

I had a similar problem last year with my buddy's car that I helped install new brakes. I installed the front calipers backwards (right caliper on the left, etc.) We were about to buy a new master cylinder when I did a search on Pelican and discovered my mistake. Hopefully I am the only one to such a thing, but it was a cheap correction.

kandhmfg · kandhmfg's Garage

Quote:

Originally Posted by SP2

I had a similar problem last year with my buddy's car that I helped install new brakes. I installed the front calipers backwards (right caliper on the left, etc.) We were about to buy a new master cylinder when I did a search on Pelican and discovered my mistake. Hopefully I am the only one to such a thing, but it was a cheap correction.

Ditto. Did the same thing, the bleeder should be on the top of the caliper. If it is on the bottom, you will get the result of firm under pressure, but then goes soft again after you release the pedal. Air Bubbles have to flow up to the top and out of the caliper to get a firm pedal.

911Etarga · 07-02-2008, 05:47 PM

The calipers are on the correct sides, all I have done is get new discs pads, brake lines and Master Cylinder. The left rear caliper is new too. But they were working before I did this, then I put in the new master, and......

I might have a faulty Master Cylinder.