Brake Pedal

[Adam 33]

Hi guys and gals

I was just wondering, when i start up my car and leave it ideling then pump the brake pedal a few times the revs go down and almost stalls.

It never stalls but it feels like it is just about to.

Is this normal or is there something wrong?

If something is wrong would anyone know what it is?

The whole car is still under warrenty, so i want to sort it out.

Thanx

Adam

[Pva_Glue]

does do that when you move your steering wheel?

only asking cuz power steering uses bit of enigne power to pump power steering...

I guess it applies same way about he brake...

BTW is your car AUTO or MANUAL?

cheers

Joe

[Adam 33]

my car is a skyline R33 GTST manual.

When you move the steering wheel the revs increase, while if you pump the brake it decreases the revs

Any ideas?

[skylark]

I believe the brakes use manifold vacuum to operate the vacuum servo unit, this is the big round black thing behind your mastercylinder that helps you put pressure into it. Repeatedly pumping the brake pedal on a cold engine would be like pulling off a vacuum line and would stuff around with the engine management. RB engines that have an issue with "idle hunt" are usually first inspected for vacuum leaks. Do the revs drop when you pull the vehicle up to a stop while driving?

[Adam 33]

Nah it doesn't do it if i leave the pedal down but if i were to release it and put it down 2 or 3 times then it will happen

[skylark]

If the brakes feel ok and you don't have to stomp on them hard to pull up the vehicle then the vacuum servo unit may not be defective/leaking. I just went out, started my r32 and pumped the pedal 3 times and the rev's dropped significantly but then returned to normal. Is there a reason you are depressing the pedal in succesion? I don't think there is anything wrong with your vehicle adam but if in doubt consult a professional mechanic.

Hope this helped

Rhys

[SLY33]

skylark, your on the money about the brake using vacuum thing.

Problem has to be vacuum related. It can be real hard to locate very small leaks in the system tho.

as lark said, is there a reason you pump the brake pedal?? Or you might just be fussy like me and think "i should be able to pump the brake pedal whenever i like, and not have any problems, this is a SKYLINE!!"

:P :D

[Adam 33]

yeah SLY33 you are right, i only got it a month ago and is still under warrenty and im just trying everything out, but if a few of you have it then it is less likely to be a problem.

thanks skylark for trying it out in you car.

Adam