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I recently changed all my brake pads with Akebonos and what a great feel that is to press down with the little effort and feel the car efficiently slowing. However, I've noticed a few times when I first start car in the morning, the pedal is hard, but as soon as car is started, it softens and gets depressed nice and softly. I wonder what accounts for the initial hard feel?
I recently changed all my brake pads with Akebonos and what a great feel that is to press down with the little effort and feel the car efficiently slowing. However, I've noticed a few times when I first start car in the morning, the pedal is hard, but as soon as car is started, it softens and gets depressed nice and softly. I wonder what accounts for the initial hard feel?
it softens because the brake booster is assisting you, engine vacuum is helping you depress the pedal via the booster
I recently changed all my brake pads with Akebonos and what a great feel that is to press down with the little effort and feel the car efficiently slowing. However, I've noticed a few times when I first start car in the morning, the pedal is hard, but as soon as car is started, it softens and gets depressed nice and softly. I wonder what accounts for the initial hard feel?
You are 100% correct about your vacuum booster being flattened out in the morning.
This starts happening on low mileage cars and there after.
There is no factory fix for this.
You can get all new vacuum pump plus new booster replaced with zero improvement...
The issue is elsewhere.
The vacuum pump exhaust its air and oil into the crankcase. When high positive pressure is present, pump has a hard time building negative vacuum.
This results in poor booster vaccum causing hard pedal.
The fix is to limit high crankcase blow-by pressure.
Booster is really sensitive to crankcase pressure.
When controlled, the brake pedal becomes soft short and powerful without quickly getting flat even after 3 weeks.
Akebonos pads on all 4x corners are a nice upgrade engineered in Japan.
Last edited by CaliBenzDriver; Jan 28, 2026 at 12:28 AM.
You should be able to test Cali’s explanation by pulling the dipstick out a little bit so pressure has a way to escape from the crankcase.
When you replaced your pads, did you bleed the brake lines? When did you last do a complete brake fluid flush?
New pads should not cause these symptoms, so it’s probably just a coincidence. Honestly, the hard feel is somewhat “normal”. There is also the vacuum pump valve that may need replacing.
It's just a matter of engine running / not running causing the behaviour described by pantomime. There is no fix, it's the normal behaviour of a vacuum operated brake booster.
He describes 'as soon as the car is started, it [brake pedal] softens'.
Getting the dipstick out on a M276 will not lower crackcase pressure, as the only opening of the tube is in the oil sump, beneath oil level. Blowing of excess crank pressure through the dipstick tube would lead to a couple of liters of oil being pushed out, before any air stats escaping. A better way to vent the crankcase would be to remove the oil filler cap.
I did not bleed the brake lines and brake fluid were flushed some 12K ago. I'll try pulling the dip stick out and unscrew oil filter cap to relieve pressure, that's simple enough. The last 4 mornings, it did not reoccur.
...Getting the dipstick out on a M276 will not lower crackcase pressure, as the only opening of the tube is in the oil sump, beneath oil level. Blowing of excess crank pressure through the dipstick tube would lead to a couple of liters of oil being pushed out, before any air stats escaping. A better way to vent the crankcase would be to remove the oil filler cap.
Correct! What was I thinking? That’s why I shouldn’t say anything before my 2nd cup of coffee.
It’s also easy to pull the line off of the vacuum valve and see if it is spitting oil. But imo this was a leftover result of pumping the brakes then starting the car.
