brake pedal get harder and harder..

[wil_rolla]

hey guys..

it's not my car but a mates.. this is what happens,,

when the car is on or driving around, each time you press the brake pedal in the pedal gets harder and harder, but with less stopping power..

the car has been in an accident and since then it has had this problem.. the car hit a poll head on..

could it be a damaged master cylinder?

we haven't flushed the fluid yet (next on the list to do)

any thoughts guys?

cheers wil

[MR22ZZ]

sounds like a problem with the brake booster, like there's no power going to the power assist.

[David the Viking]

Definitely sounds like a brake booster issue.

[CHA54]

yep, hard pedal I'd be looking at the brake booster and it's vacuum line to the intake manifold, if it's got a 1-way check valve in the line then that was possibly installed back-to-front by the panelshop.

[wil_rolla]

cheers guys,,

ok, well i got some more info,, when the car was hit it pushed the engine back abit and the engine had to be taken out, and afew things were replaced.. so as CHA54 said may be the guys didn't put the valve back the right way.. have to check this on the weekend..

i also forgot to mention it's a s15 with an sr20det..

is there anyway to check if it's the brake booster without replacing it.. just to make sure so that way we don't waste money buying one and finding out later that it's not the problem..

thanks agian for the response..

wil

[MR22ZZ]

if it's the valve causing the issues then a different brake booster will make no difference unless the valve itself is put back the correct way.

It kind of makes sense, the one way valve is there so the vacuum on the brake booter is maintained from the engine, if the valve is the wrong way around then that line is doing nothing as it's effectively been blocked. It will always be at atmospheric pressure and increases, pressurising the entire system, hence why the pedal goes so hard.

The booster itself is fine, it's the way it has been plumbed together which is the problem.

[wil_rolla]

just to be sure guys,, is it the line thats connected to the pipe sticking out of the booster in this pic.. the black pipe pointing up..

and is the valve look something like this? below.. sorry guys i couldn't find a better pic..

http://images.google.com.au/imgres?imgurl=...t%3D20%26um%3D1

wil

Edited September 4, 2009 by wil_rolla

[CHA54]

yep, the booster pipe (facing up) is meant to connect to the intake manifold, in turbocharged applications you need the 1-way valve (like you can just see in your link) installed so you dont feed the brake booster positive manifold pressure. When you install the valve back to front you dont get any vacuum assistance from the booster, which takes away any assistance the booster would usually provide...

One booster test is to put your foot on the brake with the engine off, then start the engine and the pedal should go down further once the engine starts.