JetJocks

I've just noticed this recently on my 350. The brake pedal is extremely hard to depress before engine start if the car has been sitting for more than an hour or so. Even when pressed, it barely travels enough to get the green light for the engine start button. Anyone ran into this issue and know a fix for it? When it's a short sit time and I restart the car the pedal is normally soft and depresses fine.

flowrider

iTrader: (9)

https://www.clublexus.com/forums/is-...-is-350-a.html

Lou

JetJocks

Thanks Lou, if I have any further questions with my 350 or F I'm just going to go through you directly.

2013FSport

iTrader: (2)

The vacuum brake booster uses the engines intake manifold vacuum to offer upwards of 4:1 to 10:1 mechanical multiplier to aid the driver in applying the needed mechanical pressure to push the brake pedal that actuates the calipers to clamp the pads to the rotors making the car stop.

When the brake booster leaks the stored vacuum out, equalization occurs on both sides of the diaphragm and the pedal gets hard, no vacuum assist.

The smart and cheap fix first step is replacement of the one way check valve inline with the vacuum booster near the master cylinder. Of course the gromet should also be replaced.

Vehicles operating in high humidity areas tend to be the first impacted as the debris plus moisture tend to stick in the valves seat causing a minor leak allowing the stored vacuum to escape in hours vs months.