What Makes a Brake Pedal “Hard”?

What Makes a Brake Pedal “Hard”?

Have you ever driven someone else’s car and applied their brakes for the first time – only to come to an unexpectedly sudden stop because you’re not used to the brake being so hard? That literally all it takes is about a feather’s worth of pressure to come to an immediate stop?

That simply means their brake pedal is hard. What causes hard brake pedals, you ask?

“The most obvious cause for a hard pedal is simply not enough vacuum. Any brake booster requires a minimum of 18” vacuum to operate efficiently. Anything less than that will contribute to the pedal being harder to push. If your vacuum is in the 16” to 18” range, a vacuum canister might help your situation”

If you have some mechanical knowledge of the braking system of your car, you can try the following home-based troubleshooting. Thanks to MPBrake.com for the info!


  • Check the hose running to your booster. It is not uncommon to ask for 3/8” vacuum hose at your local parts store and the kid behind the counter doesn’t have a clue that there is a difference between vacuum hose and fuel hose. He just knows it’s hose. Fuel line is not designed to resist sucking shut like vacuum hose. It will only resist expansion. Therefore, if you have the wrong hose and it is sucking shut, it doesn’t matter how much vacuum your engine makes if it is never getting to the booster.
  • The brake booster check valve could be defective. This is something easily overlooked. To check, remove the valve from the booster and disconnect from the hose supplying vacuum. Blow into the valve on the hose booster side. If air travels through and comes out the hose side, then you have a bad check valve. If you are unable to blow through, reinstall the valve and look for a different problem.
  • The whistleblowing system booster could be bad. There is a quick and simple way to check this. Follow the steps below:

A) With the engine not running, press and depress the brake pedal several times to remove any vacuum from inside the booster.

B) On the last push of the brake pedal, hold moderate pressure on the brake pedal. Don’t push like you are panic stopping, simply hold pressure like you are sitting at a red light.

C) Start the engine and pay attention to what happens to the brake pedal.

D) If the pedal drops slightly, then the booster is working correctly.

E) If the pedal does not move at all, then there is a very good chance the booster is bad.

Related Tags: Brake and Clutch Centre


If, like me, this is Greek to you – head over to an RMI approved dealer and have your brakes checked out. Brakes are one of the most important elements to a roadworthy, safe vehicle – so do not put it off!


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