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Discussion Starter #1
Hey,

My 2016 T6 Momentum is having an issue where the vacuum booster seems to leak down and the pedal is hard to press to start the car in the morning. I scanned for codes on Foxwell scanner and got 1 ABS code, C10157A, "vacuum supply, mechanical faults, fluid leakage/seal fault." Sounds expensive right off the bat and there are no leaks or any problems at all with brakes. Boost is restored right after engine fires off and there are no warning lights on. Brake fluid level was good when I looked a month ago.

Has anyone ever run across this? I saw a post or 2 with same symptoms but no solution to problem. I doubt on Volvo it is as simple as a brake booster check valve. ;)

Thanks,

Robert

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Yes. I have this happen with my 2018 very so often. As soon as car starts normal function is restored.
 

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Hard pressing brake pedal at startup has been the case from the beginning,
but only when the car hasn't been used for at least a week.
 

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Discussion Starter #4
Hard pressing brake pedal at startup has been the case from the beginning,
but only when the car hasn't been used for at least a week.
So yours has been like that since you bought it? Mine will be hard to press in 1 day. That code just makes me wonder if there is a leakage it is detecting. I don't know what the code is referring to specifically.

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So yours has been like that since you bought it? Mine will be hard to press in 1 day
Yes, it has been like that from day 1. The starter system needs to see that the brake pedal is pressed
before it will start the engine. Almost unavoidably, the remaining boost pressure will diminish over time
until you will need to press harder to activate the brake switch.
But as I wrote, it takes at least a week, perhaps even two, before this occurs.
 

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Discussion Starter #6
Yes, it has been like that from day 1. The starter system needs to see that the brake pedal is pressed
before it will start the engine. Almost unavoidably, the remaining boost pressure will diminish over time
until you will need to press harder to activate the brake switch.
But as I wrote, it takes at least a week, perhaps even two, before this occurs.
That's what is odd. Mine can bleed down in 12 hours. And my code makes me wonder if there is a bigger leak somewhere in there. Guess we will go till it breaks and rears the final culprit of the issue. :(

Robert

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That's what is odd. Mine can bleed down in 12 hours. And my code makes me wonder if there is a bigger leak somewhere in there.
You could be right, that doesn't sound normal.
If it were, there probably would have been many postst about it in the past.
But since brakes are of vital importance, and since there is a brake related code,
I wouldn't wait until it breaks. The code by itself would be enough for me.
 

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A vacuum only works when the engine is on and running. If you depress the brake pedal when the engine is of, you only have about 2-3 good pumps before you lose that vacuum assist and the pedal becomes "hard", then it merely is just brake fluid between your foot and the pads.
 
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