Bad BMC Or Bad Booster...? (S14)

[Ali 556]

hi,

OK i have this really weird brake problem...my setup is :
EVO IX Brembo Brakes all around (front and rear).
SS lines.
300zx BMC (tokico).

After installing the BMC I've bled the rear brakes...my brakes were GREAT...great pedal feel great balance and i can fell the rear brakes doing there jop,

went to the shop to install my HKS coil overs (front) after installing them i lost the brake padel...the padel we'd sink to the floor and there is no brake pressure what so ever...my frind held the idel @ 1500 rpm and i started pumping the brake to build pressure after a while the padel began to fell stiff again,

After that my brake balance is like 99% front and 1% rear whenever i'm braking to enter a corner the fronts will lock like there is no 2morrow,

So i started with bleding the WHOLE system againe (the FSM way) and still my rear brakes don't give the same feedback as B4...So I took the Rear caliper off and tested them they are ok and the front are ok too...

My friend (honda owner) said that maybe the problem is in the brake booster...or maybe the brake rod (between the padel and the booster-BMC) is bent or short....the BMC is LESS that 1K miles on it

i dunno...the same thing happened today on my way home....suddenly no brakes...thank god the road was empty...

help,

Regards,

Ali

[projectRDM]

Proportioning valve is likely bad, I've had a few do that.

[Ali 556]

where is that...BMC?

[projectRDM]

where is that...BMC?

The piece threaded into the BMC that the rear line runs out of.

[Ali 556]

you mean this :

http://i198.photobucket.com/albums/aa64/brb-/DSC03846-1.jpg?t=1234774461

and do you know how to fix it...it's brand new with less then 1k miles on it...bought it 3 months ago...damn

Ali

[brokeAs240sx]

Only way to check brake rod: unbolt the BMC & measure how much it sticks out regularly & how far it goes out on full press (actual measurements are in FSM).

To check brake booster: if your brake booster is leaking, after car is on, pump the brakes until it feels firm. turn car off. press the brake again - if you hear an air leak or if the pedal gets soft, then the brake booster is leaking.

I've had both of the above happen to me (brake booster was bad, replaced it, then forgot to check adjustment of brake rod).

bmc testing, iono, but you can probably find something in the FSM (though it may require a tool you don't have easy access to).

[Ali 556]

To check brake booster: if your brake booster is leaking, after car is on, pump the brakes until it feels firm. turn car off. press the brake again - if you hear an air leak or if the pedal gets soft, then the brake booster is leaking.



the proplem is that how much i press the padel it's still sinking away....and there is no brake bite (huge "dead" area)...b4 this whole thin happen the brakes were great !!! as soon as i press the padel BAAM the car stops....

now it's like : dead area - brake bite - how much i press on the brakes they will never lock....

:rant2: damn my 30 x 320mm rotor + 4 piston caliper are usless :squint:

Ali