Ive already posted this in the braqke section but thought id try to get to the masses, here goes

i have an sti v7 which when you rev to 7000 ish or more then go straight for the brqake pedal the brakes feel like there is no servo they are very very hard if you take your foot off the pedal then re apply they are there instantly

this problem only occurs when going from very high revs to brakes immediately after

i have ds 2500 pads front std brembos on the rear, goodridge hoses

is there a vacuum pipe to the servo that cuts out at high revs?? or am i missing something

help would be appreciated please

hawk

edited to say i have had it suggested that it may be fade but that desnt feel right, Mike Woods suggested pad knock????

i havent a clue what that is, something doesnt feel right, in EVERY other instance brakes are fine

[Edited by hawkeye - 10/14/2003 7:00:50 PM]

 

I dont have an answer to your problem but maybe beable to shed more light.
A brake servo will not be at its most efficent when the throttle is wide open= low manifold vacume. It relys to a greater exstent on manifold vacume when the throttle is shut= high manifold vac= greatest servo power/assistance.
If it was fade they would have to be very hot/hard use before hand.
Sorry, not alot of use but its the sort of prob thats hard to diagnose without driving it!


If it was a pad knock-off effect, (doubtfull) this maybe a pad choice issue, I think, and will stand corrected!

As its an STI 7, (warranty?) could you get your dealer to take a look?

Edited to say that ive just noticed you use DS2500 so you can rule out pad knock-off, these are great pads.

There is a pipe from manifold to servo, you could check it for splits ect.

Gary

[Edited by Leviathan - 10/14/2003 7:31:26 PM]

 

thanx m8 ill check it out


hawk

 

Pad knock off has nothing to do with pad material. Mike Wood is correct in that if you suffer from the pedal travelling a longer distance than normal after hard cornering, your wheel bearings are allowing the hubs to flex and push the pads away from the disks, so the first push of the pedal takes this travel up, the second gives you normal brakes.

What you are describing isnt pad knock off if you have a pedal that isnt travelling far, but the presure you have to apply is greater the first application. This sounds like either a faulty servo, faulty servo check valve, or you have a problem with the engine not generating a vacumn on overun. You may have a faulty idle control valve or a sticking throttle buterfly. Do you find when you are sat stationary and you rev the engine, it takes a while to drop the revs back down to a slow idle?

 

Thanx for the reply john i havent noticed the idle thing ill go check and post result tomorrow, i will say though the problem ONLY manifests itself when you are accelerating hard and THEN immedately go to brake irrespective of cornering or not


thanks again ill go check, could it have anything to do with the induction pipe are there any connections i should check?


hawk

 

thanx john & mike ive found out the problem (well the garage has!!!!!!) the pipe that connects from the servo to the manifold has a one way valve in it (should be one way but wasnt working properly) the dealers mechanic went out in the car first came back ashen faced and said f@@k me that cars go not brakes when youre on boost I said i told you so he said hold on, then swapped a new pipe from a demo car and hey presto its fixed.


result!!!!!!!! thanks everyone THIS IS WHAT SCOOBYNET IS ALL ABOUT

hawk

ps a cyber apple is in the post john...

 

pleasure, glad its sorted.