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Petza, that's a great process to use for any kind of pad as you are ensuring a consistent thermal load and cooling without shocking the system.
Just to make one input, for the 997 platform, utilizing the parking brake after bedding new brakes is fine. The only time you do not want to set the parking brake is if your parking brake mechanism is built in with the rear caliper, such as Audi/VW. The 997, 996, and many other vehicles use a drum brake style of parking brake so setting it after bedding in your brakes is fine. The reason to not set your parking brake for vehicles that have the integrated rear brake system is because once the p-brake is set, it can cause a hot spot on the rotor where the the entire rotor wont cool at the same rate and it can deposit more compound specifically on that spot that can cause buildup and judder with longer use as the pads are engaged on the rotors. This is also applied to an EPB (electronic parking brake) system. The EPB though a separate component clamps pads on to the rotor itself instead of the hat structure as drum brakes do.
The rotors still get hot during bedding and even though the parking brake doesn't work with the calipers and pads on the running surface, but inside the rear rotor hub, like a drum, I still don't set the brake as I don't want to trap heat anywhere on the rotor the first time that could create a warpage or have brake material bond to the metal.
i bedded the brakes, but still squealing. I took the car back to my Indy who looked for mechanical issues (found none), took the pads off, cleaned them, and stuck them back on. There was no squeal for the first few minutes of my drive home, but the squeal returned, quite possibly louder than ever. I took the car back to my mechanic who was totally stumped. Brakes are new, rotors are new with fewer than 250 miles on them.
Next step is my mechanic is going to swap out the textar pads and try another brand. He said he’s never had any issue like this with this specific brand of pads.
Anything else i can try? Thanks for everybody’s ideas. Much appreciated.
Did you replace either the factory pad dampeners or use an anti-squeal paste when reassembling.
On and S, the rubber pads with metal prongs lock into the caliper piston on the rear and the fronts have a cylinder that goes into the caliper piston. On the fronts you need to apply paste around the cylinder and on the rear of the pad surface. Either of these will work.
On the rears you need to use the OEM dampeners and you'll need a 4 28mm & 4 30mm - Suncoast sells them.
My mechanic replaced the Textar brake pads with Brembo pads. Still squealing. I took it back to the mechanic who put the car on the rack, and was ready to try replacing the rotors. When the car was lifted, he tried spinning the front wheels and realized that they weren’t quite spinning freely (there was a small amount of resistance when manually spinning the wheels). There was also a very faint high pitched noise when spinning one of the wheels (couldn’t be produced on every spin and almost inaudible if not looking for the sound).
My mechanic now is pretty convinced that the squeal is mechanical, possibly from the calipers being too tight, a slight imperfection on the wheels (I have 19 inch Ruger avante gard rims), or possibly the brake master cylinder. He will be taking the car in mid-September to diagnose the issue.
My mechanic replaced the Textar brake pads with Brembo pads. Still squealing. I took it back to the mechanic who put the car on the rack, and was ready to try replacing the rotors. When the car was lifted, he tried spinning the front wheels and realized that they weren’t quite spinning freely (there was a small amount of resistance when manually spinning the wheels). There was also a very faint high pitched noise when spinning one of the wheels (couldn’t be produced on every spin and almost inaudible if not looking for the sound).
My mechanic now is pretty convinced that the squeal is mechanical, possibly from the calipers being too tight, a slight imperfection on the wheels (I have 19 inch Ruger avante gard rims), or possibly the brake master cylinder. He will be taking the car in mid-September to diagnose the issue.
Any other thoughts on what this squeal could be?
Caliper could be sticking. Neither of the other possibilities makes any sense to me. Master Cylinders don't squeak, they leak or don't hold pressure, and how does a wheel squeak - it's bolted to the hub. I would guarantee you if you brought me the car I could eliminate the brake squeal with proper assembly, using pad dampeners, anti-squeal paste, and a correct bedding procedure.
The squeal is not happening during the first 10 minutes of driving make me think that something is getting hot and expanding, which is causing that squeal.
Forgot to mention that after the 20 minute drive to the mechanic, the front wheels felt abnormally hot, and considerably hotter than the rears when we manually spun them. Don’t know if that is normal, but my mechanic seemed somewhat surprised by the high temperature of the front wheels.
The squeal is not happening during the first 10 minutes of driving make me think that something is getting hot and expanding, which is causing that squeal.
Forgot to mention that after the 20 minute drive to the mechanic, the front wheels felt abnormally hot, and considerably hotter than the rears when we manually spun them. Don’t know if that is normal, but my mechanic seemed somewhat surprised by the high temperature of the front wheels.
That sounds like stuck calipers. How often was your brake fluid flushed as the water absorbing properties can cause corrosion inside the caliper and them to hang up. Be careful with that as you can boil the fluid and effect braking ability. If they're getting that hot, they're likely glazing the pads and or rotors and that's what's causing the squeak. You won't be able to get that to go away until the cause of the problem is corrected.
45 years ago a disc brake job included rebuilding the calipers ... removing the piston and honing the cylinders. There would always be a rust ridge to deal with. Failure to do this would create the over heating and other symptoms you are describing.
How often do you flush the fluid? If not often then water could be a problem.
I thought of one additional possibility. As rubber brake lines age, the rubber actually swells, narrowing the internal passageways. OEM rubber Porsche lines are reinforced with a fabric or cloth type membrane sandwiched between the inside and outside rubber sections in order to give the line strength and rigidity so that when you press on the pedal and transfer hydraulic force to the lines, most of that force goes to pressing the caliper pistons against the pads, which press against the rotors and provide stopping power, instead of the lines expanding and providing for a mushy brake pedal. On an 11 year old car, the rubber may have swelled and in that case, the internal membrane works against you because the line can't swell out, and swells in, narrowing the passageway. When you press on the brake pedal, you're exerting substantial force on the fluid through the line and that force is able to push the pistons, but when you let off the pedal, the fluid is supposed to relax and not keep the pressure on the caliper pistons. If the lines have narrowed enough, this reverse flow of fluid may not be happening efficiently and that's why the pads are staying on the rotor and the brakes dragging. If you'll be doing additional brake work, I'd suggest picking up a set of the DOT approved Speigel braided stainless brake lines for the 997. Not only does the braided stainless provide for a more structurally sturdy line for better brake feel, but they're internally lined with Teflon, which doesn't react with the brake fluid and swell up. They are also coated on the outside to not abrade anything they come in contact with and vice versa. I have them on both my 997s.
Also, if you had a Master Cylinder problem, almost all master cylinders these days are dual-channel, which means the hydraulics for 2 wheels are separated from the hydraulics for the other 2 wheels and they don't separate them with both fronts on one channel and both rears on the other, they do left front and right rear and right front with left rear. The reason this is done is to provide some balance to the braking if one channel fails and they're dual-channel so you don't lose all braking with a channel failure, just half your braking. If they separated them with both fronts on one channel and that had a hydraulic failure (or fluid in that channel boiled), then you could have a dangerous situation where only the rear brakes activate and the car swaps ends when trying to stop. What I'm getting at is if you had a Master Cylinder problem, one front and one rear brake would be dragging or hot, not both front brakes.
It's also probably unlikely that both front calipers become sticky at exactly the same time. In your situation, I'm leaning toward swollen rubber brake lines first and dragging caliper pistons second.
I can't speak to the 997.1, but I could swear that I read somewhere that the 997.2 brake lines were already Teflon lined and "upgrading" to braided stainless was not required. Is this wrong?
I’m not sure how often the brake fluid has been flushed. I have only owned the car for four months. It has 126,000 miles on it, but only 26,000 miles on a new engine.
Thanks so so much for the thorough walk through of what could be happening to the calipers and the brake lines. Sounds like one of those is the likely culprit for the squeal.
I can't speak to the 997.1, but I could swear that I read somewhere that the 997.2 brake lines were already Teflon lined and "upgrading" to braided stainless was not required. Is this wrong?
You may be remembering Bruce in Philly's post where he cut a rubber brake line to inspect. I believe what he found is that they were reinforced as I described, but not Teflon lined so you could still have the swelling issue.
I was driving in freeway traffic this morning with the windows down and I heard more squealing. It was actually more of a squeak, and audible at around 10-15 mph. It sounded almost like an old squeaky bike. The squeak got slightly faster as I sped up, inaudible at around 20 mph, and was inaudible under 8 mph.
Attached is a video of the squeak.
Does this sound shed any more light on whether it could be swollen rubber brake lines or dragging caliper pistons (or something else)?
I was driving in freeway traffic this morning with the windows down and I heard more squealing. It was actually more of a squeak, and audible at around 10-15 mph. It sounded almost like an old squeaky bike. The squeak got slightly faster as I sped up, inaudible at around 20 mph, and was inaudible under 8 mph.
Attached is a video of the squeak.
Does this sound shed any more light on whether it could be swollen rubber brake lines or dragging caliper pistons (or something else)?
Not really. That squeak is the pads lightly touching the rotors. After you stop, forcing them against the rotor, then start up again, they're still lightly touching the rotor surface as there's nothing mechanical that pulls them away from the rotor, they're just not being forced against it anymore. You don't hear it below 8 MPH because the rotor isn't rotating through the pad gap fast enough to create the harmonic that makes the squeak and above 15MPH, it's either spinning so fast that the harmonic becomes undetectable or the pads have had enough time to move a bit further away from the rotor. The only way to eliminate that noise is with something that will absorb or dampen the harmonic vibration that creates the noise. This is the purpose of the rubbery anti-squeal adhesive that applies to the rear side of the pads and bonds it to the caliper pistons or the OEM dampeners where the metal prong resides in the piston and the caliper piston contacts the rubber pad part of it.
Did you ever find what was causing the squeak? I have the exact same problem and can't figure it out. Only squeaks after driving for 15 minutes or longer and only when lightly touching the brakes. It's driving me crazy!
07-19-2018, 05:51 PM
