Zmonsta

About 9 months ago, I swapped out the front pads bc PO didn't have the right pads in there, it didn't sweep all the rotor surface, short of 1/2" from the center. I had some some constant faint noise like pads slapping rotor at a high frequency rate immediately after, and I resolved it by using some brake quieter behind the pad and grind a bit of pad backing to ensure full pad surface swept rotor's face. took care of the noise for last 9 months until I did a track day yesterday. Just an FYI: the last time I tracked this car was about 1.5 yrs ago, when it had old pad and rotors, and I didn't have any problems on track.

Yesterday, it didn't feel right, the brakes constantly were overheating, and I can smell it after just a few laps, I had to take it easy to let it cool, and still when I came in after each session, everyone can smell it.

During lunch at the trackday, I drove it at normal speed to a local gas station to fuel up. I started to hear the brake clinging/squealing noise constantly until I dabbed at the brakes, then it would disappear. Once I let off the brakes, it would resume. It did it at all speeds. Despite this, I continue the 2nd half of the day, but definitely drove with much reservation.. And the drive home was horrible, the noise was constant whenever I was not braking. It sounded bad, louder than at lunch

I jacked it up today and found the rotor to be very difficult to turn, like the caliper pistons were stuck and could not retract. The rotors surface had a ring in the middle that seem to indicate overheating. That could explain why my pads were heating up so much during the session. I bled it with my Motiv bleeder, and at 12psi, the fluid came out slow (not dripping slow, but it certainly did not squirt out with force).

I have read that the flexible rubber hose can expand over time and cause the piston to not retract. Or the caliper may need to be rebuilt.

I can do both myself, but I'm wondering if 996 calipers with 103k miles may already need to be rebuilt. That's quite soon in my opinion. Or could there be something else.

Anyone need to replace their 996 or Boxster rubber lines yet due to similar problem?

Appreciate any comments or opinions.

Thx,
Herb

Van

Sounds to me like it's probably a sticking piston in the caliper - and will require a caliper rebuild.

Ubermensch

Agreed. Pull the pads and see if you can retract the piston. It sounds stuck.

Obviously mileage can impact the life of parts, but it's not the only thing. Damage to the caliper during pad changes, or just bad luck/debris can cause a failure as well.

-Shawn

nick49

A couple of things happen when using the brakes hard in a short period of time like tracking/ racing etc.

The hard braking causes rapid wear of the pad. The pads on multi piston calipers, even with differential bore sizes do not wear flat and straight. They wear beveled or have a taper to them. This causes the pistons in the caliper to **** or cant in the bores which in turn makes pad retraction difficult. To further aggrevate the situation, the spent brake pad material can essentially deposit itself on the pistons making it difficult for them to retract.

Sometimes with use the problem may correct itself to a degree, other times it will require cleaning the pistons, if needed, and fitting new pads. If the pads still have a lot of material left sometimes using a sanding device and dial caliper to restore uniform thickness will work.

GL

Barn996

I changed the front pads and rotors on my '05 GMC truck last fall and had debris(chunk of rust) get wedged in between the new rotor and new brake pads. The debris created a high spot on the pads, but was quickley worn down, although the brakes smelled for a few miles.

Zmonsta

Thanks guys, I am going to try and retract the piston later this week. Likely I will just order the rebuild kit and new lines since I will be getting into it. Will update you all if this resolves it.

Zmonsta

Here is an update. It seems the PET only shows a p/n for the dust caps (which I thought would come with piston seals), but it didn't when the package arrived from Sunset import. since PET doesn't show a number for the piston seals, what gives? Should the seals have been included with the dust caps? I got all 8 caps in 4 little packages and didn't see the piston seals in any of them.

Ubermensch

I've never rebuilt Porsche calipers specifically, but the one set I did on my Supra didn't have any separate seal for the pistons. The pistons are a slip fit to the caliper cylinders. The dust boots are there to protect the bore from dust and damage. I suspect if you remove the boots, and then the pistons you can clean things up and reassemble. Hopefully someone that's worked on Porsche calipers can chime in.

-Shawn

CWhaley

PNA does not sell the inner viton o-ring seals... They want you to replace the calipers. You can get them from StopTech... http://www.zeckhausen.com/Brembo/Con...es.htm#Rebuild

mikemdd

Rebuilding the caliper may very well cure the issue, especially if they were overheated. However, I had exactly the same symptoms and it turned out to be the master cylinder was causing the problem. Could have just been debris or blockage, but after replacement, no more problems.

Zmonsta

@mikemdd, thanks for the info. Was this on your SC or GT3?

I rebuilt my calipers with pads and lines since, and have not had any issues yet, but I've only been road driving it. Hopefully, the issue is cured during my next track day which won't be for awhile from now (importing car to Brussels for next years). If it comes back, I will update this thread.

thanks all for the details.
Herbert

mikemdd

My problem was on my SC. After coming off the track the front brakes would not retract (right front worse than left front). They would then drag for a while and finally release. I replaced the rubber with steel brake lines and still had the problem. I had heard from others about the master cylinder in the older SC's and it definitely solved my problem. No problems since then.

Shark Attack

I would certainly stay away from track days from now on