Stiff brake pedal in the morning

[Jim-p]

Hi all,

Hasn't been a great 2024 so far, already have an epb issue on another post which needs sorting.

Anyway, something new over the last few days. In the last week I've noticed the brake pedal being stiff in the mornings, as if I had pumped it. After starting, it softens and works away as normal.

Have read online, I gather that it's loosing vacuum while parked over night. It could be due a leaking check value off the booster. A leaking booster itself or a leaking master cylinder.

Has anyone else experienced this?

Fluid was flushed and changed at 122k, now at 167k, due to be flushed again at 182k.

Thank you.

[yossarian247]

It can only really be a slight leak in the booster, valve, vacuum pump, or the associated vacuum pipework causing this. I don't see how a fault with the master cylinder itself could cause a vacuum leak. When the engine starts does the pedal feel immediately return to normal? If so I don't think I would necessarily consider it a fault as such. All the MOT test checks is that the brake pedal sinks slightly after the engine is started, indicating that the servo is building up vacuum. 

[Jim-p]

3 hours ago, yossarian247 said:

It can only really be a slight leak in the booster, valve, vacuum pump, or the associated vacuum pipework causing this. I don't see how a fault with the master cylinder itself could cause a vacuum leak. When the engine starts does the pedal feel immediately return to normal? If so I don't think I would necessarily consider it a fault as such. All the MOT test checks is that the brake pedal sinks slightly after the engine is started, indicating that the servo is building up vacuum. 

Thank you, yes it returns to normal once started. Would I be better off to get it sorted anyway?

[yossarian247]

I've owned a few cars where the brake servo didn't appear to retain much if any vacuum overnight (I think our 2012 Avensis diesel was always like this too) and as long as the brakes worked correctly when the car was being driven normally I never worried about it. It appears to be the norm on some makes/models.

[Jim-p]

Oh great, I will just keep an eye on the braking so to make sure there's no deterioration.

Thank you

[Cessna]

4 hours ago, Jim-p said:

Oh great, I will just keep an eye on the braking so to make sure there's no deterioration.

You say it only started doing it recently. My 2015 car does not do it either. Therefore it seems something has changed or failed on your car recently. I would get it checked soon to ensure things don't get worse.

[avensis_2018]

start with changing/refreshing the braking fluid.

 

 

enjoy.

[yossarian247]

On 2/19/2024 at 4:50 AM, avensis_2018 said:

start with changing/refreshing the braking fluid.

 

 

enjoy.

Brake fluid wouldn't have any effect on the servo holding vacuum, surely?

 

 

[Dava]

I thought that I had a similar issue, but it turns out that it was my knees getting old :)

[Roy124]

My Yaris Cross is exactly the same.   Foot on brake,  hard, select Ready mode and the pedal depresses.

I got home an hour ago, just checked the pedal, it depressed.  I can't recall it being any different. 

[Roy124]

Right, just returned to the car, power off, brake hard and then softened and depressed.  Definitely not related to any powered pump.