Brake Pedal Hard to Press Down, Below Freezing

Maintenance/Repairs
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1

2014 Acura TSX, 4 Cylinder, AT, about 160k miles

Two days ago when I got in my car, the brake pedal was really hard to press down. This was after it sat overnight, and it’s within single digits so extremely cold. The car was very difficult to stop and I had to press the brake pedal down with great force. I gave the brake pedal several hard presses in rapidly, and then everything was fine. I think it’s likely some moisture got in the brake booster or hose and froze? Looking on ShopKey, this car doesn’t appear to have a check valve in the hose that goes to the brake booster. I know some cars have this check valve seperate from the brake booster, and it’s easy to remove from the vehicle and rattle it around to see if it’s stuck close or open. But I think on this car it’s integrated into the brake booster? I tried checking ShopKey and couldn’t find anything about a check valve. I think in this case, it’s likely the brake booster that got moisure in it? Me pressing the brake pedal down several times with great force might have free up the ice that might have formed?

2

When was the last time the brake fluid was flushed?

Brake fluid by nature absorbs moisture out of the air. And if enough moisture is in the brake fluid that moisture will freeze creating a extremely hard brake pedal.

Tester

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3

Thanks for the reply. A little less than two years ago, and a little less than 40k miles ago. I guess I could use a brake fluid pen tester in the master cylinder, and then go from there?

4

https://www.brakeandfrontend.com/tech-tip-hard-braking-when-cold-lack-of-power-assist/

Tester

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5

The vacuum check valve is in the vacuum hose, in-line near the firewall. There could be moisture in the check valve or vacuum line.

More likely the brake power booster is failing, do you hear hissing while holding the brake pedal down?

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6

I do not hear any hissing sound. I heard some manufacturers integrate them with the booster. Looking at the parts diagram

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There’s clearly something there from the two clamps, I just can’t find a part for the actual valve. I likely have to buy the whole hose assembly? Part 8 is just a clamp. I also checked on like Rock Auto, and cannot find just the valve.

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The check valve in included with the hose assembly. Before ordering any parts, remove the hose and examine the hose/valve to see if there is any reason for a vacuum loss.

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8

Hey thanks. How did you find this? I tried searching for “Brake Booster Hose” “Brake Booster Line” Brake Booster Vacuum” “Brake Check Valve” and so forth and cannot find it in ShopKey, the diagram and instructions you show.

9

Service manual under Vacuum brake booster; testing and inspection.

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