Brakes spongy only after moving car

SEBASTIANFROMNJ

MEMBER
2009 FORD FOCUS
2.0L
4 CYL
2WD
AUTOMATIC
100,000 MILES

We replaced brake booster and master cylinder. Booster did have brake fluid inside of it from leaking master. Bled manually then ABS bleed, then manually again. Brake pedal pumps hard when off and when car is on. However, once you try to move even half a rotation of the tire the pedal reverts to being spongy and stays that way until you pump them up again.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

If this is happening only after you move the vehicle then the ABS is most likely the issue. The ABS pump has what is called an isolation valve inside of it and it is what controls the fluid to all the wheels.

So the brakes are getting spongy because this valve is actually bleeding the pressure which acts the same as a leak.

What I would do is unhook the ABS control module connectors and see if this still happens. What I suspect is happening is the ABS is activating as soon as it sees wheel speed input.

If this is the case then unplugging it so that it doesn't see the wheel speed and it should stop. If this is the case then you need to replace the control unit. Here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-replace-a-abs-controller

Below you will find the process from the manual on how to replace this. Please run through this and let us know what you find.

Thanks

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