SC brakes

Situation yesterday: Front calipers on my '83 SC shot. Pistons will hardly move. Pads very difficult to remove. Brake pedal very firm, but not a lot of stopping power.

Situation today (after installing new rotors, pads and calipers (NEW calipers, not rebuilt) and bleeding the system with ATE Super Blue from rear to front): Soft pedal with what seems to be a lot of travel. Pedal does not "pump up". Brake warning light stays on. It was not on yesterday. Car stops fine; much better than it did yesterday.

Concerns: Pedal travel and brake warning light. Do I need a new master cylinder? If so, why has this become obvious only after I replaced the front calipers? If not, then why in the world does the brake warning light stay on?

t almost sounds like air in the lines...the spongey pedal anyway.

Porsche master cylinders may not automa-tically reset the light after it detects a pressure imbalance (which would occur when you bled the brakes). Some have a reset button on the switch while others may require the switch to be removed for the shuttle piston (that turns the switch on) to recenter.

To reset the warning light, pull the negative cable from your battery and then put it back on again.

Spongy brakes indicate air in the line. However, there is alot of mismatching between all kinds of surfaces right now, the upshot of which is a spongy feeling. The rotors are new to the pads, which in turn are new to the pistons, etc. As each wears in, following your next bleed operation, the pedal will quickly start to feel tighter and more firm.

But you probably do have air in the line as well. You might take this time to pull the brake warning switches from the side of the master cylinder. With someone in the car, slacken off the brake warn switches, one at a time, and have the brake pedal pushed down to purge out the air and the sludge that commonly falls into the areas of these switches.

You may have to reset your warnng switch many times before your car decides the equality between the two braking systems has been met.

Jw

I've got some great info from this and the rennlist forum. The light is out, so my fingers are crossed for the MC. I'm going to give things a couple hundred miles to sort themselves out. If there's still too much pedal travel for my liking and taking it in to have it pressure bled and have the MC checked. I'm also going to make sure the pedal free-play is adjusted.

Before you do anything rash, consider my experience. I rebuilt my front calipers and had the same symptoms, except for the brake warning light. I had good braking power, but too much pedal travel. Once the brakes were working, the pedal was firm, but there was too much pedal travel to get there.

Upon further inspection, I could see a gap between the pads and rotors. There should be none. I was told this would fix itself in a few hundred miles, but I was skeptical and anxious.

So, one by one I removed the pads, blipped the brake pedal, and then wedged the pad back in. This eliminated the gap, and eliminated the unwanted pedal travel. I believe this is just caused by the new seals wanting to flex instead of slide, along the piston.

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'83 SC

I did the same procedure that Superman described after my caliper rebuild, and the long initial pedal travel was gone. I replaced each pad, one at a time, with a slightly thinner piece of wood, pressed the brake, and then replaced the pad. Worked great!



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Bill Krause
'79 911SC Euro

Beautiful. I'll give it a try this weekend. Thanks Superman and Bill. I'll let you know how it works out.

I too have long pedal movement. I had the wheel out yesterday and did notice about a 1mm gap between the pad and the rotor.

I like the technique described by Bill. I'll try it out.

Tony
'78 911SC

This procedure was spelled out in a thread that Warren called the "hysterisis thread". I'm not exactly sure how it works, but it does.

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Bill Krause
'79 911SC Euro