[Cloud9...68]

When I recently replaced my front brake pads, I didn't think to open the bleed screws when retracting the pistons into the calipers. As a result, a small but noticeable amount of fluid leaked out of the master cylinder as a result of "driving it in reverse." No additional fluid leaked out after I reassembled everything, nor has any leaked from subsequent driving, inculding the brake pad bedding procedure. Does the fact that the cylinder leaked when pushing fluid through it in the reverse direction indicate the seals are weak, and that it needs to be replaced soon, or is it "normal" to leak a little when doing what I did? In other words, is this an early warning that the master cylinder is on its last legs, or is it something I can put off for awhile?



By the way, I can't say I notice any real improvement in braking performance from installing the much-lauded Porterfield pads. They're not bad, they just feel pretty much the same as whatever was in there before. Maybe it's because my car has calipers from a 1988 944 Turbo S (the pads are HUGE compared to the stock 968 pads) and Zimmerman cross-drilled rotors, so I've already got pretty hefty braking capability compared to a stock car. Also, I haven't taken it to the track yet with the new pads, so maybe I'll see an improvement there. It's also interesting that they emit EXACTLY the same level of squeaking, both in volume and in pitch, as the previous pads. Too early to tell about the dust level. Thanks.

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[jaap]

Did it really leak from the master cylinder (inside cabin or engine bay?)? I would expect some fluid to overflow from the fluid container on top of the master cyclinder when it was full and the pads were fairly worn which would have required moving the pistons back quite a lot.



Jaap

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[benspeeder]

That leakage would be normal - done that on race cars before.



Let those pads bed into those rotors over the next couple hundred miles - they should grab.

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[flash]

no "leaking" is normal - it is normal to have fluid push back up through the reservoir when you push the pistons back - anything getting past the master seal though indicates a weak seal - this may or may not show up as a leak during operation - i would flush the system to make sure that you didn't pick anything up on the back stroke though



i agree about the pads - go bed them in (see the stop tech site for that procedure) and then see how they squeak



note: if you did not surface the rotors first, the pads will never bed in properly

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[xrad]

Ditto: fluid under pressure acts in similar fashion in all directions.....so, when you step on the brake pedal OR push fluid back into master (with pedal in normal position), there should be no leak . fluid in reverse direction should bubble up into reservoir. Usually, this is dirty fluid in the distal lines...so better method is to crack bleeders as you stated. But, takes longer to do....

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[Cloud9...68]

It leaked from inside the master cylinder (probably past the seals) down the firewall in the engine compartment. I cleaned it up as best I could. It definitely didn't bubble up through the reservoir. I've changed pads on many other cars, never thinking to open the bleed screw when retracting the pistons, and I've never had this happen before. But again, not a hint of a drop has leaked since then from driving it. I'm guessing the seals are a little tired, but I'm not convinced replacing the master cylinder is urgent. I'll definitely keep an eye on it, though.



As far as the pads, I did follow the bedding procedure recommended by Stoptech, and I had the rotors turned, so they were properly surfaced. Again, I'm not saying the pads are bad, just that I can't tell any differnce compared to the old ones. But that's typical for me - other than the Sumitomo HTRZIII tires I put on the car recently, I can't remember the last time I did anything to the car that actually caused me to notice any difference (the "magic" MAF spray, Iridium plugs, new distributor cap and rotor, sea foam throttle body cleaner, etc.). Maybe I just don't have a well calibrated backside (or those of you who claim to notice improvements from this stuff all have more vivid imaginations than I do - kidding!) Hopefully the next trip to the track will reveal something...

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[benspeeder]

I must be missing something here - retracting the pistons without opening the bleeder can cause fluid to overflow the top of the master cylinder - it would need to be filled a little on the high side to overflow it but that's not abnormal.



What am I not getting here?



Whup - on the second read - if it leaked from inside the master cylinder and didn't overflow the filler on the the top - that's not normal.

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[xrad]

yep...and brake fluid loves H20, so that you can plan for loss of firewall and booster paint, followed by rust......if not cleaned up...or maybe the back-filling fluid just topped off your MC booster...

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