Brake pedal to floor today 991.1 S
#1
Racer
Thread Starter
Brake pedal to floor today 991.1 S
Took the 2013 Carrera S 991.1 out to a thing this morning, a 20 min high speed highway run to a Cars & Coffee. Got off highway exit ramp. Brakes normal. Turned onto a small side road for a few hundred yards. Goosed it in 2nd, then as I was slowing down (rapidly) at traffic light w revs quite high, the brake pedal went right to the floor and had almost no brakes. Very soft pedal all the way to floor. Pumped brake once and regained braking and stopped at the light halfway through the intersection. Pulled off. No trail of fluid behind car. Restarted car. Brakes completely normal.
Um... what ... the... heck. This was unexpected.
Fluid was flushed (allegedly) at Porsche dealer in Dec 2023.
Obviously something is up. I hadn't been braking to a degree enough to overheat fluid prior and my highway offramp stop wasn't overly aggressive just prior to the side road. I've noticed a bit of soft spot at top of brake pedal recently (when compared to my other cars) but have read here it's sort of normal for a 991.1 Carrera S.
Should I just have the brake fluid changed ? Any other ideas?
No leaks or brake fluid warning light and level in reservoir is good. Fluid looks clear/clean.
The only thing I could think was some weird vacuum booster or master cylinder issue ... I was in Sport+ and the car was at maybe 6500 RPM's slowing down in 2nd.
Had plans to go on a mountain run with a couple guys after but tapped out as I don't have any confidence in the brakes just yet... under different circumstances could have been disastrous.
Um... what ... the... heck. This was unexpected.
Fluid was flushed (allegedly) at Porsche dealer in Dec 2023.
Obviously something is up. I hadn't been braking to a degree enough to overheat fluid prior and my highway offramp stop wasn't overly aggressive just prior to the side road. I've noticed a bit of soft spot at top of brake pedal recently (when compared to my other cars) but have read here it's sort of normal for a 991.1 Carrera S.
Should I just have the brake fluid changed ? Any other ideas?
No leaks or brake fluid warning light and level in reservoir is good. Fluid looks clear/clean.
The only thing I could think was some weird vacuum booster or master cylinder issue ... I was in Sport+ and the car was at maybe 6500 RPM's slowing down in 2nd.
Had plans to go on a mountain run with a couple guys after but tapped out as I don't have any confidence in the brakes just yet... under different circumstances could have been disastrous.
Last edited by Nashvegas; 05-18-2024 at 03:38 PM.
#2
Rennlist Member
That’s only happened to me on the track. And I was using my brakes really hard and then came off the the track and that’s when my brakes boiled. To think that can happen on the street would seem to require a lot of brake usage.
I would get the braking system inspected.
I guess it’s possible you have air in the line or the fluid is quite low.
I would get the braking system inspected.
I guess it’s possible you have air in the line or the fluid is quite low.
Last edited by Mike Murphy; 05-18-2024 at 04:08 PM.
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Nashvegas (05-18-2024)
#3
Hydraulic brake systems are simple, just fluid in a close system. In order to achieve what you described you would need either change in fluid properties (ie; boiling, air), loss of fluid (leak) or change in volume in the system (pad/caliper shifted).
Pumping the brakes sounds like it got the system filled back up and got them working again. Makes me lean toward something changed in the volume of your system. Did you have a stuck caliper piston that suddenly freed itself? Did a brake pad's friction material break off?
Pumping the brakes sounds like it got the system filled back up and got them working again. Makes me lean toward something changed in the volume of your system. Did you have a stuck caliper piston that suddenly freed itself? Did a brake pad's friction material break off?
#4
Im not sure if it could be related
But there is a small rubber hose that goes to top of master cylinder which gives up. Air in the system does wierd things. You can see it because the connection end splits.
As this is brakes I would make sure I know what happened to not die. Any good wrench will be able to track it down.
As this is brakes I would make sure I know what happened to not die. Any good wrench will be able to track it down.
#5
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With a 2013, it’s about the right time for the seals on the piston inside the brake master cylinder to be damaged from a rusted inner cylinder due to the first brake flush being done in ‘23.
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Nashvegas (06-02-2024)
#6
Three Wheelin'
#7
Racer
Thread Starter
Thanks for the thoughts gang. Agree it is probably something simple. Good ideas above.
Today I put the 991 on top of the stacker for a peek (it's usually parked underneath)... Checked all 4 corners. Nothing amiss I could find. (I did not remove wheels so could not verify all pad portions were intact). No evidence to indicate something coming apart or burning up or fluid loss.
Brake fluid's been changed every year or two since new at dealers. Only like 20 something k miles on the car. Pads front and rear are genuine Porsche, rears replaced about 5500 miles ago of street driving, friction material thickness is good where I could see it. Have no service history on front brakes ever being done but surely they were... (or maybe not?).
After my inspection, I went about 50 yards down the block and hear loud grinding from right rear wheel as I slowed down from maybe 15mph to 0 at the first stop sign-- definitely a new noise. Pedal felt normal though. This grinding noise did not repeat and rather annoyingly a podcast was on (Spikes Car Radio and they were playing intro music loudly on so coudn't hear it 100%).
So I've scheduled a dealer visit on their website. I love a good mystery. I'm sure they'll change fluid and tell me it's fine.
Today I put the 991 on top of the stacker for a peek (it's usually parked underneath)... Checked all 4 corners. Nothing amiss I could find. (I did not remove wheels so could not verify all pad portions were intact). No evidence to indicate something coming apart or burning up or fluid loss.
Brake fluid's been changed every year or two since new at dealers. Only like 20 something k miles on the car. Pads front and rear are genuine Porsche, rears replaced about 5500 miles ago of street driving, friction material thickness is good where I could see it. Have no service history on front brakes ever being done but surely they were... (or maybe not?).
After my inspection, I went about 50 yards down the block and hear loud grinding from right rear wheel as I slowed down from maybe 15mph to 0 at the first stop sign-- definitely a new noise. Pedal felt normal though. This grinding noise did not repeat and rather annoyingly a podcast was on (Spikes Car Radio and they were playing intro music loudly on so coudn't hear it 100%).
So I've scheduled a dealer visit on their website. I love a good mystery. I'm sure they'll change fluid and tell me it's fine.
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#8
Rennlist Member
Thanks for the thoughts gang. Agree it is probably something simple. Good ideas above.
Today I put the 991 on top of the stacker for a peek (it's usually parked underneath)... Checked all 4 corners. Nothing amiss I could find. (I did not remove wheels so could not verify all pad portions were intact). No evidence to indicate something coming apart or burning up or fluid loss.
Brake fluid's been changed every year or two since new at dealers. Only like 20 something k miles on the car. Pads front and rear are genuine Porsche, rears replaced about 5500 miles ago of street driving, friction material thickness is good where I could see it. Have no service history on front brakes ever being done but surely they were... (or maybe not?).
After my inspection, I went about 50 yards down the block and hear loud grinding from right rear wheel as I slowed down from maybe 15mph to 0 at the first stop sign-- definitely a new noise. Pedal felt normal though. This grinding noise did not repeat and rather annoyingly a podcast was on (Spikes Car Radio and they were playing intro music loudly on so coudn't hear it 100%).
So I've scheduled a dealer visit on their website. I love a good mystery. I'm sure they'll change fluid and tell me it's fine.
Today I put the 991 on top of the stacker for a peek (it's usually parked underneath)... Checked all 4 corners. Nothing amiss I could find. (I did not remove wheels so could not verify all pad portions were intact). No evidence to indicate something coming apart or burning up or fluid loss.
Brake fluid's been changed every year or two since new at dealers. Only like 20 something k miles on the car. Pads front and rear are genuine Porsche, rears replaced about 5500 miles ago of street driving, friction material thickness is good where I could see it. Have no service history on front brakes ever being done but surely they were... (or maybe not?).
After my inspection, I went about 50 yards down the block and hear loud grinding from right rear wheel as I slowed down from maybe 15mph to 0 at the first stop sign-- definitely a new noise. Pedal felt normal though. This grinding noise did not repeat and rather annoyingly a podcast was on (Spikes Car Radio and they were playing intro music loudly on so coudn't hear it 100%).
So I've scheduled a dealer visit on their website. I love a good mystery. I'm sure they'll change fluid and tell me it's fine.
#9
Racer
Thread Starter
Update:
1 -- Ran it through the dealership week before last, and they did a very thorough job, but couldn't find anything wrong. The tech did what seemed to me to be a comprehensive and thoughtful report back, put some miles on it, drove it home, yada. The intermittent issue did not arise while in their care, as I'd expect. No air in lines, fluid is fine and new. Note: We think the grinding noise was an unrelated rattle on deceleration, btw.
2 -- Then this weekend on a road rally on Oregon mountain roads, brake pedal went to the floor twice. Both times again while decelerating with high RPM. As you would imagine, this could result in a serious situation. When these instances occurred, as before, brakes were absolutely not overheated or overused (so like right when I started driving, etc) -- it is a seemingly random occurrence. And as with before, one quick panic pump, full braking came back, pedal has nice "bounce / push back" and feels perfect. Obviously, I backed off. The roads were were on had no guardrails, drop offs... etc.
3 -- Then, yesterday while coming home, after putting along, I found myself sitting in line at a gas station, I went to move the car forward, flat ground in a parking lot -- the brakes were cool and unused. Brake pedal went straight to floor again while sitting still!. Again, I released brake pedal, and full brake feeling came back with one pump. And I think the fact that the car was not moving (0 mph) this rules out an ABS issue. Perhaps that is incorrect but it seems plausible to me.
For those of you with more experience with 991 platform -- does this mean I need a new master cylinder? It's intermittent but I can't imagine what else this is. It seems that the dealer won't replace anything that they can't diagnose.
Have already texted the service department to see what they think. But this is crazy.
Took this pic at Hells Canyon Overlook @ Upper Imnaha River on Sunday just before the brake pedal went to the floor ...
1 -- Ran it through the dealership week before last, and they did a very thorough job, but couldn't find anything wrong. The tech did what seemed to me to be a comprehensive and thoughtful report back, put some miles on it, drove it home, yada. The intermittent issue did not arise while in their care, as I'd expect. No air in lines, fluid is fine and new. Note: We think the grinding noise was an unrelated rattle on deceleration, btw.
2 -- Then this weekend on a road rally on Oregon mountain roads, brake pedal went to the floor twice. Both times again while decelerating with high RPM. As you would imagine, this could result in a serious situation. When these instances occurred, as before, brakes were absolutely not overheated or overused (so like right when I started driving, etc) -- it is a seemingly random occurrence. And as with before, one quick panic pump, full braking came back, pedal has nice "bounce / push back" and feels perfect. Obviously, I backed off. The roads were were on had no guardrails, drop offs... etc.
3 -- Then, yesterday while coming home, after putting along, I found myself sitting in line at a gas station, I went to move the car forward, flat ground in a parking lot -- the brakes were cool and unused. Brake pedal went straight to floor again while sitting still!. Again, I released brake pedal, and full brake feeling came back with one pump. And I think the fact that the car was not moving (0 mph) this rules out an ABS issue. Perhaps that is incorrect but it seems plausible to me.
For those of you with more experience with 991 platform -- does this mean I need a new master cylinder? It's intermittent but I can't imagine what else this is. It seems that the dealer won't replace anything that they can't diagnose.
Have already texted the service department to see what they think. But this is crazy.
Took this pic at Hells Canyon Overlook @ Upper Imnaha River on Sunday just before the brake pedal went to the floor ...
Last edited by Nashvegas; 06-18-2024 at 12:21 PM.
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RwdConnor (06-18-2024)
#10
Racer
Thread Starter
(PS I know the talk track about "why am I going to dealer with this?" I plan on giving the dealer one more shot before I just go to my indy Porsche specialist and tell them to replace the master cylinder on my own dime. The car is CPO and it would be nice if Porsche paid the bill for something while under CPO... )
#11
Rennlist Member
that is really crazy that it keeps happening, even while not moving. I'm no expert, but the master cyliner sounds very plausible.
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Nashvegas (06-18-2024)
#12
I would tow the car to the dealership and get it sorted.
Fortunate you didnt' crash.
I had a similar problem in our Jeep, and it was an intermittently stuck caliper that resolved when I replaced it.
Fortunate you didnt' crash.
I had a similar problem in our Jeep, and it was an intermittently stuck caliper that resolved when I replaced it.
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#13
Rennlist Member
I would think it's you master causing the issues. For some reason it's allowing air in either through a crack seal or something. If there's no air in the system and all the lines are tight on the calipers (would see fluid leaking if they weren't) and the fluid hasn't boiled it would narrow the issue down to the master.
#14
If it's under CPO. Have it towed to dealer and insist they make it right.
changing master cylinder and or calipers should be covered. Pads and rotots not.
Loosing brakes off and on is a serious issue.
changing master cylinder and or calipers should be covered. Pads and rotots not.
Loosing brakes off and on is a serious issue.
#15
Update:
1 -- Ran it through the dealership week before last, and they did a very thorough job, but couldn't find anything wrong. The tech did what seemed to me to be a comprehensive and thoughtful report back, put some miles on it, drove it home, yada. The intermittent issue did not arise while in their care, as I'd expect. No air in lines, fluid is fine and new. Note: We think the grinding noise was an unrelated rattle on deceleration, btw.
2 -- Then this weekend on a road rally on Oregon mountain roads, brake pedal went to the floor twice. Both times again while decelerating with high RPM. As you would imagine, this could result in a serious situation. When these instances occurred, as before, brakes were absolutely not overheated or overused (so like right when I started driving, etc) -- it is a seemingly random occurrence. And as with before, one quick panic pump, full braking came back, pedal has nice "bounce / push back" and feels perfect. Obviously, I backed off. The roads were were on had no guardrails, drop offs... etc.
3 -- Then, yesterday while coming home, after putting along, I found myself sitting in line at a gas station, I went to move the car forward, flat ground in a parking lot -- the brakes were cool and unused. Brake pedal went straight to floor again while sitting still!. Again, I released brake pedal, and full brake feeling came back with one pump. And I think the fact that the car was not moving (0 mph) this rules out an ABS issue. Perhaps that is incorrect but it seems plausible to me.
For those of you with more experience with 991 platform -- does this mean I need a new master cylinder? It's intermittent but I can't imagine what else this is. It seems that the dealer won't replace anything that they can't diagnose.
Have already texted the service department to see what they think. But this is crazy.
Took this pic at Hells Canyon Overlook @ Upper Imnaha River on Sunday just before the brake pedal went to the floor ...
1 -- Ran it through the dealership week before last, and they did a very thorough job, but couldn't find anything wrong. The tech did what seemed to me to be a comprehensive and thoughtful report back, put some miles on it, drove it home, yada. The intermittent issue did not arise while in their care, as I'd expect. No air in lines, fluid is fine and new. Note: We think the grinding noise was an unrelated rattle on deceleration, btw.
2 -- Then this weekend on a road rally on Oregon mountain roads, brake pedal went to the floor twice. Both times again while decelerating with high RPM. As you would imagine, this could result in a serious situation. When these instances occurred, as before, brakes were absolutely not overheated or overused (so like right when I started driving, etc) -- it is a seemingly random occurrence. And as with before, one quick panic pump, full braking came back, pedal has nice "bounce / push back" and feels perfect. Obviously, I backed off. The roads were were on had no guardrails, drop offs... etc.
3 -- Then, yesterday while coming home, after putting along, I found myself sitting in line at a gas station, I went to move the car forward, flat ground in a parking lot -- the brakes were cool and unused. Brake pedal went straight to floor again while sitting still!. Again, I released brake pedal, and full brake feeling came back with one pump. And I think the fact that the car was not moving (0 mph) this rules out an ABS issue. Perhaps that is incorrect but it seems plausible to me.
For those of you with more experience with 991 platform -- does this mean I need a new master cylinder? It's intermittent but I can't imagine what else this is. It seems that the dealer won't replace anything that they can't diagnose.
Have already texted the service department to see what they think. But this is crazy.
Took this pic at Hells Canyon Overlook @ Upper Imnaha River on Sunday just before the brake pedal went to the floor ...