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Re: the vacuum idea, the tech last dealer visit said that if there is a vacuum issue, usually you lose brake boost and pedal gets harder (not soft) -- he also said that vacuum issues usually throw a code and he checked for any vacuum codes. I mean, I guess that makes sense. But I am not going to accept "no code = no problem" for this one !
The service advisor got me in tomorrow so ... I'll update. I can't be the only one with a bad master cylinder so far on a 991.1 I'm sure !
Is the fluid level decreasing at all? If yes, there’s a leak somewhere.
I’ll bet this is a master cylinder issue. Not a vacuum issue or stuck caliper. A stuck caliper could have to retract itself, and even still, only 1/2 of the brakes would be faulty. Pedal going to the floor is air (which has been ruled out), or MC.
Is the fluid level decreasing at all? If yes, there’s a leak somewhere.
I’ll bet this is a master cylinder issue. Not a vacuum issue or stuck caliper. A stuck caliper could have to retract itself, and even still, only 1/2 of the brakes would be faulty. Pedal going to the floor is air (which has been ruled out), or MC.
Fluid level is unchanged. It's right at Max on the reservoir and has been there after each loss of braking event. (Each time I've pulled over, looked at all 4 calipers, the reservoir, and the barrels of the wheels - expecting to see fluid loss somewhere -- but none is evident)
Thank you everyone for your ideas, much appreciated. All of this will prove helpful in discussing with the service folks.
Brake fluid's been changed every year or two since new at dealers.
That doesn’t make complete sense. The interval is every two years. Not every year or two. That’s motor oil.
Are you sure you see a charge for brake fluid on your service records every “year or two?”
I ask because a friend of mine took his car - not a Porsche - to the dealer every year for “scheduled service” and they never changed his brake fluid. He only figured this out when he asked my why he’d replaced rear calipers, a clutch slave, and a clutch master and I made him go through his records.
After 10 years he was replacing a hydraulic component every 6 months.
That doesn’t make complete sense. The interval is every two years. Not every year or two. That’s motor oil.
Are you sure you see a charge for brake fluid on your service records every “year or two?”
I ask because a friend of mine took his car - not a Porsche - to the dealer every year for “scheduled service” and they never changed his brake fluid. He only figured this out when he asked my why he’d replaced rear calipers, a clutch slave, and a clutch master and I made him go through his records.
After 10 years he was replacing a hydraulic component every 6 months.
Prior to this melee, the car had a brake fluid change approx every 2 years.
5 plus the one when bought it in Dec 2023 which was done slightly ahead of schedule as part of svc to get it CPO’d.
12 years old. 2 years. 6 changes.
The car has the service booklet stamped (old school style) by the service dept at the original dealership in SC. All very precise and one of reasons I bought it.
I think it has to be the master cylinder. When you step on the brakes, you just push noncompressible fluid through a rigid line. If the pedal goes to the floor, the fluid is going around the plunger/seals rather than the plunger pushing it through the line. A frozen caliper or frozen slave would cause the pedal to be hard. The seals in your MC seem to be worn. It’s surprising that your Porsche dealer didn’t tell you this. I think it’s pretty clear that you need either a MC rebuild or a replacement. The fact that you only have 20 k miles on an 11 year old car, is also indicative of bad seals. If the rubber seals are not used, they can shrink. I’m happy that you’re still alive. This will be difficult to fix after your car is totaled and you are dead.
The noise is unrelated as is the intervals of your fluid change.
Last edited by Denny Swift; 06-19-2024 at 10:17 AM.
Just got the car back from the dealer. 3.5 weeks in the shop. Unfortunately techs could not duplicate the issue so it made replacing parts a bit tricky. I did a drive around with the shop foreman / lead tech at some point a few weeks ago. Nice chap to race around the block with... and he is clearly a Porsche enthusiast.
Dealer replaced the master cylinder under CPO warranty + full bleed from all 8 caliper ports again. Have only driven 10-15 miles since. Brake pedal feels abnormally softer than it did before to me but brakes function ... we shall see. Hopefully this is resolved because at this point, every time I'm about to stop I do a quick blip test on the brake pedal to confirm they're going to work.
PS - Dealer was great and parked the car either under cover or used my windshield sunshade. I was not stoked about the 100+ degree temperatures for the past week here in Oregon and the leather dashboard - one hot week and I hear they can start delaminating on the older cars like mine. Part of the delay is that the software company CDK was hacked and the dealer was essentially at a standstill for a week or two of the car being there. (CDK is a software company that does the dealer software, and they were hacked, and paid a 25m ransom or something - ridiculous situation all around but it meant they couldn't order parts, communicate with customers, etc). Overall a very good dealer experience though and I'm happy as a clam to have the blue car back.
06-18-2024, 09:18 PM
