Marc3.4V6

iTrader: (1)

Imagine you're on a hill when you start your car, you're coasting down riding the brake and suddenly it feels as if you've lifted your foot off the brake and back on it, only you've been on them the entire time. It only lasts a second, but it could be dangerous. What should I look for? Master cylinder?

joe77

air in the line? have you had the abs block bled by a gm tech 2?

mitchntx

iTrader: (14)

So the pedal stays at the same point, just a brake pressure change?

I would check the vacumn line or the check valve in the booster. Also, check the grommet in the booster that seals the check valve.

Marc3.4V6

iTrader: (1)

yes mitch that's exactly what happens. I had a brake fluid flush and refill and a dealership maybe 6 months ago. I'll check that stuff. Thanks.

DONAIMIAN

iTrader: (18)

Since you said it happens at startup I'm gonna agree with the the brake booster/vac line theory.