Brake pedal goes to floor overnight... any ideas?

Hi all,

Having a bit of an issue here with my brakes, and it seems to be a strange one…

So first thing in a morning, after the car (ep3 type R) has sat maybe 12/13 hours, my brake pedal goes to the floor, if I pump the brakes with the engine on or off, it starts to build resistance and then the brakes work fine, getting progressively better the more the brakes are pressed.

With the engine off if I pump the brakes the pedal goes hard, when starting the car the pedal depresses so I’m guessing this rules out any vacuum issue?
There is no fluid being lost, I’ve checked this every day for the past week, marking a line on the reservoir just to be sure, no leaks.

This only happens if the car has sat for a while, for example if I drive to work and they’re good, I’m at work 8 hours then drive home, the brakes are fine.

Discs and pads are fine, fluid was replaced around 3k miles ago. This isn’t something that has really got progressively worse, I left the car while I was on holiday for a week then noticed it, now it is a daily occurrence if I leave the car for more than 12 hours.

Any ideas? I haven’t done anything so far, I’m going to give the brakes a bleed and see if that makes a difference but I don’t think it will, I think I have an issue with the MC/Servo, but im not sure?

Cheers,
Ell

Sounds like a seal has gone somewhere to me and the brake pressure isnt being kept up.... Im not that versed in the brake system beyond the calipers though unfortunately so i cannot offer more.

It also sounds like to me that the system has air in it. I would start with bleeding the calipers first. Of course start with the Caliper closest to the reservoir.

ellb123 said:

Hi all,

Any ideas?

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As said air is in the system, or a seal in the master cylinder is crapped out. Could be a slave cylinder issue. Small chance something is up with the calipers causing the pads to back of the discs, but it's unlikely. My money would be on a seal in the MC allowing fluid to pass over time.
Not going to be the servo as if faulty the brakes would feel 'better' ie firmer pedal, you've shown it's working as the pedal goes lower\softer when starting the car and introducing the vacuum to the servo.

Finally, please stop driving it with a potentially serious brake fault. This is what's known as a Bad Idea.

SmegHead said:

As said air is in the system, or a seal in the master cylinder is crapped out. Could be a slave cylinder issue. Small chance something is up with the calipers causing the pads to back of the discs, but it's unlikely. My money would be on a seal in the MC allowing fluid to pass over time.
Not going to be the servo as if faulty the brakes would feel 'better' ie firmer pedal, you've shown it's working as the pedal goes lower\softer when starting the car and introducing the vacuum to the servo.

Finally, please stop driving it with a potentially serious brake fault. This is what's known as a Bad Idea.

Click to expand...

Good advice. If the pressure suddenly drops without warning while driving then you will only be left with a handbrake.... That could take a while to think about and then stop and by then someone will be dead or your car written off.