Brake pedal feel

[mitch_f1]

So my pedal is usually a bit soft, which I can deal with; I drive around it. But if I use the brakes after accelerating hard and holding gear higher in the rev range (5k or so), then the pedal is maybe 50% or more stiffer. I've only recently noticed this, just wondering if it is normal.

[manga_blue]

Servo vacuum non-return valve or diaphragm leak? Does it hold vacuum for long after you switch the engine off? Haven't heard of it in an MX5 before though. Sort of a British car specialty.

[mitch_f1]

That's what I thought, but pumping the brake with the engine off produces a very very stiff pedal. I will maybe get 5 pumps before it is immovable.

[manga_blue]

That's normal for pumping to use up the residual vacuum like that. If there's a leak then it would be losing vacuum pretty quickly with engine off and no pumping.

[mitch_f1]

So you mean if I left it and went to push the pedal, it would be hard if there were a leak?