So, I've posted a few times before about odd brake problems I've been having, with brakes dragging and what-not. I've narrowed down the symptoms list and here's what I have:

(1) On start-up things are normal. Brake pedal has the usual 1cm or so of travel before it starts to bite down.

(2) When driving around normally/on the freeway, brakes are fine.

(3) When decelerating, this is what does it. If I go down a long hill engine braking, at the bottom, the brakes are dragging. The pedal feels really hard and the brakes get VERY sensitive, like the moment you touch the pedal it throws you forward. Also the brakes drag.

If I start accelerating again, esp. boost, within about 20 seconds the brakes are back to normal.

I saw the same kind of problem before (except the brakes were dragging always) and people said it was the MC. However, in my case it would seem to be vacuum related or something. Is there some kind of checks I can do before I start replacing parts left and right?

Thanks.

 

Bump. Anyone?

 

Sounds like there might be air in the lines...try bleeding them and see what happens. If possible, it wouldnt hurt to get some SS brake lines and install them.

 

I would try what he said^^^^. Check the fluid levels and everything, such as leaks etc. Other than that I dunno what to tell you. Good luck, keep us updated.

 

Sounds like air in lines. Bleed system and see if you still have the same problem.

 

That could be your problem. Brake master cylinders use engine vacuum, seems to be related to me with the long engine braking and brakes being weird.

There are ways to test your MC but i can't remember. You could check vacuum lines leading to mc. I think you can also keep pressure on the pedal for a period of time to see if vacuum escapes while at idle. maybe someone else can chime in.

and why is everyone saying air in lines?

 

Your description suggests low vacuum at low rpm's. Unless you're using aftermarket cams, you might have a punctured/loose vacuum hose

 

Your brake booster could be having issues. Your boost uses the vacuum to help you apply more pressure to your brakes. There is a check valve in the line that goes from your brake booster to you intake manifold that lets vacuum pull, but not let boost back in. This is because you can't boost while braking because your foot is no longer on the gas pedal. If you booster is warring out or you have done something to you car for you motor to generate more vacuum then normal your brake booster could be pulling you pedal in causing your brakes to be slightly on or extremely touchy. This is something I have never experienced but that’s how the system works so if you brakes are touchy and responsive I wouldn't think its fluid related.

Hope I helped
Johann @ Girodisc