Brakes spongey at first, then harden up as car is driven – trapped air?

[Gareth Randall]

My 2002 Ford Escape needed a new front brake flexi-hose to pass its annual UK safety inspection last week. I was annoyed with myself for not noticing it and replacing it myself before the inspection, since I would have saved over £100 in parts and labour costs, but anyway.

The Escape came back from the shop with fantastic brake feel, but now it’s a week later, and after it’s been sitting for a few hours the brakes are spongey as hell. You have to pump the pedal before you set off to get it back to up proper hardness. Once it’s there, it’s fine – until it’s been parked for a while.

I’ve never experienced this before; I’ve never had brakes that were spongey at first but then hardened up. I’ve experienced trapped air in the brakes, but that has caused them to be permanently spongey until properly bled; they wouldn’t harden up no matter how much you pumped them.

Does this sound like a simple trapped air scenario that will be sorted with a re-bleed? Or could it be something else, like a failing master cylinder?

The shop that did the work is long-established and highly reputable in the area; they’ve been doing my inspections for the last 6 years. Obviously, even the best shop isn’t immune from unintentional mistakes, and I got the car back from them with the brakes feeling absolutely rock-solid, so it’s not like they forgot to bleed them. It’s a week later that this problem has started to occur.

I’d be under the car right now looking at the brake system, were it not dark, freezing cold and hammering down with rain.

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