GRUWEZ

Guys,

Sorry for all the newbie questions, but here I go again. As some of you may recall, I am having issues with the brakes on my 1997 993 Turbo. The inner brake pads do not really touch the rotors. I have checked out the calipers. The fronts require some cleaning but they should be OK with new spring plates and seals. The rear calipers are just fine as they are.

With my limited knowledge of the braking system on this car, I have been thinking if perhaps the master cylinder or the hydraulic pump is failing. Just a wild guess from me, so I am turning to the collective wisdom of this forum to help me out.

Apart from rusty rotors, I also experience a spongy brake pedal. For what it is worth, after the car has been standing for a week, it takes about a minute for the brake pressure warning light to go out after I start up the car.

The brakes have been bled and the brake fluid replaced by a Porsche dealership only last year.

Any idea what could be wrong?

Regards,
Rik Gruwez
Brugge, Belgium

Spartan

How do you know the pistons on that side are ok? Take that caliper off and one by one use compressed air blown through the bleeder screw to make sure the pistons do extend (they may shoot out but you get the idea). Use something to block the rest of the pistons from shooting out while you do this.

If you have done something similar already and have rebuilt and re-bled the caliper then I would then start looking at your other brake system components. I think this is caliper related though as its a matter of the pistons not extending the brake pad to the rotor on one side only.

911/Q45

What he said, must be a bad caliper. Perhaps it's a defect that you can't detect by looking. The brake warning light will come on for a bit after start up until the pump gets the system up to pressure, this is normal.

Full Boost

Another thought along the same vein....

If your PADS are not positioned correctly (and i know you have pulled the caliper and tried what has been mentioned above - then they could be binding ???

Anothe thought is that if the accumulator isnt bleed propedly - than i find I get a softer pedal too - But hey thats just me - I have been known to be sensitive

Simon.

TT Surgeon

Slave cylinder/acumulator as Simon mentioned. Could be your rotors are warped?

GRUWEZ

Hi Simon,
All four calipers checked out OK with compressed air. Pistons popped out nicely without binding.

How do I bleed the accumulator? I have heard about a special electronic tool to open the ABS valves. Does this mean the accumulator has to be bled at a dealership?


Front rotors are fine. Rear ones are severely rusted, but that is because the pads were not touching them.