Rebuilt Calipers-Powerbled -Soft -Needs 2 Pumps for Brakes

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Gary Apotheker
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Rebuilt Calipers-Powerbled -Soft -Needs 2 Pumps for Brakes

#1 Post by Gary Apotheker »

The "Greyfox", a 1964 C Coupe, which has been under my care since 1983 and has now come out of about a 16 year of hibernation. With a full top to bottom checkup, amongst which was the brake system.

All the calipers were removed, sent off to be professionally rebuilt, and re-installed by my favorite mechanic, who has seen me through 5 different Porsche's (all of which have been track driven).
The system was closed up and bled with a Power bleeder, and the brake pedal was firm, with little travel, just like in the old days.

The dilemma...

Once the car was pulled out of the shop the brake pedal went to the floor, with virtually no brakes. It takes pumping the pedal, once, or twice, (in anticipation of stopping), and then pushing it again to stop the car. The car does stop but the pedal is still soft, and there is about 1/2 distance of pedal travel before engaging occurs.

I was told that this situation would occur and that it would correct itself after about 1500 miles of driving. Me, "in my"need to know brain", am curious as to why this is happening, what makes the situation exist, and the correction to then mysteriously occur.

In my curiosity, dilemma and confusion I have done a lot of research, amongst which was deciding to read the Ate Repair kit Instructions that come with the rebuild kits. I am curious about the instruction noted below.

Assembly, Instruction #5

"Adjust the position of the piston step (Fig. 8) with the ATE piston turning pliers (Fig.7) and check it with a 20 degree piston template (Fig.9).
Exception: pistons with 0 degree step adjustment (Fig. 10): here, spacer plates are used and are so assembled that the recessed piston step and the full part of the plate lie on the leading side of the brake disc by forward rotation."

Any pertinent responses to my brake situation, and the Ate instructions would be greatly appreciated.

The Fox :?:

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Ron LaDow
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Rebuilt Calipers-Powerbled -Soft -Needs 2 Pumps for Brakes

#2 Post by Ron LaDow »

Gary,

"I was told that this situation would occur and that it would
correct itself after about 1500 miles of driving. Me, "in
my"need to know brain", am curious as to why this is happening,
what makes the situation exist, and the correction to then
mysteriously occur."

"They all do that". Seriously, the factory, in order to avoid fitting a booster, used every bit of mechanical and hydraulic ratio they could find. As a result the best C pedal will be 'low' compared to a drum brake car.
What's more, in a fresh rebuild, the piston/square-section O-ring location still isn't where it needs to be and it/they will find that location sometime soon. Finally, that 'self-adjusting' mechanism in each piston tends to hold bubbles for a while; they will also work themselves out and get bled the next time you do it. I know it's disconcerting, but I've never had redone discs that didn't do exactly as you mention.
Thanks,
Ron LaDow

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Ron LaDow
www.precisionmatters.biz

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Jim Breazeale
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#3 Post by Jim Breazeale »

Gary

It will clear itself up in 100 or so miles, not 1500! Your brakes are acting just like they were expected to act.

Regards
Jim Breazeale
www.easypor.com
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David Menere
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Rebuilt Calipers-Powerbled -Soft -Needs 2 Pumps for Brakes

#4 Post by David Menere »

Ron and Jim have already given the collective wisdom on what to expect when bleeding 356 disc systems. I'd only add that if the brakes don't improve, you may have to try priming the master cylinder (ie removing it, filling it with fluid and pumping it/working it around to ensure all air is flushed).

That said, it seems a bit curious that the pedal was ok immediately after bleeding, then deteriorated.

As to the Ate instructions, these are to ensure that the brake pad applies approximately equal pressure across its face- for even wear. Without this step in the piston, the disc would tend to drag the leading edge of the brake pad toward it- similar to the servo action on a leading shoe drum brake. The step reduces the applied pressure at the leading edge of the pad, so lessening the servo effect and applying more even pressure across the pad face.

Let the List know how you go with this one.
David Menere
356SC

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Dave Mitchell
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Bleading C brakes

#5 Post by Dave Mitchell »

Another trick I used last year on the "Rat Rod" my 65 C after rebuilding the brakes and installing all new lines was to lightiy tap on the lines and calipers to dislodge any air that could have been trapped in the lines or adjusters. I used a vacume bleader and as it was pulling fluid out is when I tapped on the lines and calipers. I used a full two quarts of fluid out of the calipers and once done they were hard as a rock and I never had to blead them again.

Hope it helps......your results may be different......... :wink:
Dave Mitchell
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Fred Gruendig
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BLEEDING C BRAKES

#6 Post by Fred Gruendig »

GARY,
THIS IS THE SAME THING THAT HAPPENED TO ME AFTER A FULL REBUILD.
IT WOULD TAKE 1-2 PUMPS TO BRING THE PEDAL UP. IF I WAITED A FEW MINUTES THE SAME THING WOULD HAPPEN.
SOMEONE TOLD ME TO TAKE THE PADS OUT. PUT BACK 2 THINNER BLOCKS OF WOOD AND STEP ON THE BRAKE TO ALLOW THE PISTONS TO COME OUT A LITTLE. PUSH THE PISTONS BACK IN AND INSTALL THE BRAKE PADS. MY BRAKES NOW STAYED UP BUT WERE STILL SOFT.
WITH THE FRONT CALIPERS UNBOLTED FROM THE ROTORS MY WIFE WOULD PUMP THE BRAKES WHILE I BLED THEM WHILE TURNING EVERY WHICH WAY. A LOT MORE AIR CAME OUT.
THE REAR CALIPERS I BLED THE STANDARD WAY.
MY BRAKE ARE NOW FIRM AND UP AT THE TOP. IT WOULD OUT PERFECT.

FRED
#3877
65'SC COUPE

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