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2016 CTS 3.6 Premium, 2013 ATS 3.6 Premium
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Discussion Starter #1
Several times in the past few days, when I go to start the car by putting my foot on the brake, the pedal feels very hard and won't depress much. When the engine starts the pedal travels normally, as it usually does even when the car is off. It doesn't seem right. Has anybody experienced this problem?
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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It looks like your booster is losing vacuum. I can be a bad check valve or grommet and hopefully not a bad booster. The check valves are very inexpensive. A good one will hold vacuum for months if not years.
 

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Discussion Starter #3
My dealer "could not reproduce" the problem in the week they had my car. This despite the fact that the hard brake pedal is now happening after the car sits for less than an hour. I want to make it easy for them when I bring the car back next week and show them the parts to replace. I found the grommet but I'm not sure which part is the check valve. Is it the Bosch part that plugs into the grommet, or is it the smaller inline part marked with a question mark in the picture?

Grommet.jpg

CheckValve.jpg
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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Off hand i don't see the check valve in either picture but I'm suspicious it may be inside the hose that connects to the booster. It looks like there is a sensor for measuring vacuum at the end of that hose.
 

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Discussion Starter #5
Here is a picture of the vacuum hose. Do you think that part in the middle is the check valve?

https://www.amazon.com/dp/B014RF2R9A/

Since it's all one unit, maybe I should ask the dealer to replace the whole thing plus the grommet to see if that helps.
 

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Discussion Starter #6
I took my car in again and demonstrated the problem. The dealer replaced the vacuum hose and check valve. It didn't make a difference. They called GM and GM said it was normal for the brake booster to lose vacuum after 30 minutes because my car has special motor mounts that leak vacuum apparently. I asked them to replace the brake booster or find the leak. They are keeping the car until Monday to see if the service manager is willing to do that. Pretty bogus. Does the lemon law apply to problems that GM claims are normal?
 

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Discussion Starter #7
I convinced my dealer to keep on trying. So far he has replaced the vacuum hose, check valve, and brake booster, yet the problem persists. Sometimes the booster will still have vacuum after sitting overnight. Most times it won't. Same for short rests of 1/2 hour or so. What else could be causing the problem? There's not much left to replace. Could the master cylinder be to blame?
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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I convinced my dealer to keep on trying. So far he has replaced the vacuum hose, check valve, and brake booster, yet the problem persists. Sometimes the booster will still have vacuum after sitting overnight. Most times it won't. Same for short rests of 1/2 hour or so. What else could be causing the problem? There's not much left to replace. Could the master cylinder be to blame?
That's a curious one. About the only other thing I can think of is that getting in or out of the car you may be depressing the pedal while the engine is off and depleting the vacuum. If the pedal is not returning all the way to the top after you apply it, it may cause the vacuum to bleed off. For a test, make a point of lifting the brake pedal with your toe when you get out to see if that helps any the next time you restart.
 

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Discussion Starter #9
I performed your experiment a couple of times. The pedal was firmly up as far as it would go when I tried to lift it after turning off the engine and removing my foot from the brake. Even so after 30 minutes the vacuum was gone. I tried pushing the pedal as hard as I could in that state and it barely moved an inch, not nearly as much as it goes down when it has vacuum assist.

After driving a number of loaners, I can say that the brake pedal on my car has to be pushed in farther before the brakes take effect. The car still has good stopping power, but the brake pedal has to move pretty far for that to happen. I'm pretty sure it wasn't like that when I first got the car.
 

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Several times in the past few days, when I go to start the car by putting my foot on the brake, the pedal feels very hard and won't depress much. When the engine starts the pedal travels normally, as it usually does even when the car is off. It doesn't seem right. Has anybody experienced this problem?
I have the same problem.tried to start the car in the morning. The brake pedal was at the top of it's travel,and very hard. No free play. Tried to start the engine with foot on brake. Nothing happened. I thought I had a dead battery. I was about to call AAA. Finally gave it one more try. This time I pushed very hard on the brake pedal. It took a lot of effort to depress the pedal . Just enough to engage the starter.
Does anyone know if there are any service bulletins regarding this problem?
 

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Several times in the past few days, when I go to start the car by putting my foot on the brake, the pedal feels very hard and won't depress much. When the engine starts the pedal travels normally, as it usually does even when the car is off. It doesn't seem right. Has anybody experienced this problem?
It was the brake pedal switch (I think that was what it was called and I found that info on line and made them replace it) on my XT5. They replaced that and it was fine for awhile. It did the exact same thing that yours was doing and after 6 months is doing it again so it is going back for another one. If is the master cylinder they said it would have low fluid and it did not have that... Good luck
 

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I have the same problem.tried to start the car in the morning. The brake pedal was at the top of it's travel,and very hard. No free play. Tried to start the engine with foot on brake. Nothing happened. I thought I had a dead battery. I was about to call AAA. Finally gave it one more try. This time I pushed very hard on the brake pedal. It took a lot of effort to depress the pedal . Just enough to engage the starter.
Does anyone know if there are any service bulletins regarding this problem?
Lots of us are having this problem. The dealer says "they can't find a problem and have tested everything." I have had to take my car in multiple times. Last time they replaced the brake switch and it was great for months. It is back now. Tired of leaving my brand new XT5 at the dealer for weeks at a time with zero results. It is there right now AGAIN> Wish I had kept my Honda...
 

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2019 V-Sport Prem Lux satin steel/cashmere
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My 2019 v-sport does this but starts fine, the brakes work fine once started and have the right brake pedal travel once started. When I took my v-sport out of winter storage, I reconnected the battery and when I went to start it the brake pedal was rock solid hard, barely moved a fraction, but it started fine and the brake pedal then went to normal pressure.
 

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2015 V-Sport
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Mine does the same thing and has since I owned it. Hard to press the pedal at start but goes to normal once the engine is running. I have had my V-Sport for nearly 5 years and have asked the dealer about this issue and get the same answer as everyone else has. Seems like a very minor issue as long as the breaking is fine after starting the car. I can live with this. :cool:
 
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