Can we talk about the difference a proper brake fluid flush makes on an older car?

I had a 2008 Civic come in last week with the owner saying the pedal felt soft. It wasn't a leak, but the fluid in the reservoir looked like dark coffee. I did a full flush with a pressure bleeder, about two quarts of new DOT 4. The change was night and day. The pedal went from a mushy, long travel to a firm, short stroke in about 30 minutes of work. It's one of those jobs people skip because the brakes still 'work', but the fluid had absorbed so much water over 5 years it was basically boiling at a lower temp. The owner called me back to say it felt like a new car. Has anyone else had a customer be that surprised by a basic service they'd been putting off?

3 comments

3 Comments

moore.beth14d ago

Honestly, that's the perfect example. People forget brake fluid is meant to be changed, not just topped off. I've seen the same thing on trucks where the fluid gets so bad it actually eats at the inside of the brake lines over time. That mushy feel is basically the fluid getting spongy from all the water it soaks up.

aaron74014d ago

But what if that spongy feeling isn't always from old fluid? Couldn't it just be air in the lines from a bad bleed job? I've topped off my brake fluid for years and never had a problem, so maybe the whole change interval thing is overblown for normal driving. If the fluid isn't dark, why fix what isn't broken?

taraross14d ago

You're missing the boiling point problem. Old fluid absorbs water and boils easier under hard braking, creating air bubbles in the lines that feel exactly like a spongy pedal. The color doesn't tell you the boiling point has dropped. You can't see the water mixed in, but it turns to steam when you need your brakes the most.