Brake problem: Master cylinder or prop valve

[MR-VTEC]

Hey guys, just a quick one before I go pulling things apart or buying parts. I got issues with my front brakes not engaging. Rears seem to engage when the brake pedal is pressed but the fronts don't.

I'm thinking it's either a problem in the prop valve or the master cylinder as the rears work fine.

Anyone had this happen or any suggestions on what the problem might be?

Cheers for any help

[trism]

Wouldn't be master cylinder, that would affect front and rear.

It'll be prop valve, or air in the front lines.

Honda's are linked diagonally, not front/rear.
Sent from my custard cannon like Peter North.

[gensport]

i would suspect the master cyl. what the prop valve does, is exactly what it states, proportion. Its common for master cylinders to by-pass fluid form one piston to another. The best way to check is to carefully clamp off the brake lines and check the pedal. If its rock hard, master is ok, but if it sinks (sometimes this can be a slow sink with light pedal pressure). its the master. If your not sure, get it checked by a qualified tradesman, as you don't want to be taking chances with brakes..

[grifty]

the master cylinder has primary and secondary pistons, theres an easy way to check it.

undo the two pipes going to it and bleed the master cylinder, that should show you if you are getting pressure on both the primary and secondary pistons.

thats very weird you saying only the rears engage.

hondas braking system is setup so if you have 1 half of the braking system fail the other half still works. each half consists of 1 front and 1 rear.

maybe your front calipers are seized?

[gensport]

thats not exactly correct, while they have primary and secondary pistons, if you undo them, and put your finger over, you can never reproduce the pressure needed for a by-pass... plus you will need to bleed the cyl again. The system is a dual diagnal(from memory) after the proportioning valve. If a component was to lose pressure, it would have to be a leak (check around calipers, wheel cyl, prop valve) if there is no sign of a leak... its by-passing in the master.

[MR-VTEC]

thanks for the help guys. i'll try test the mc first

[MR-VTEC]

Oh by the way when the brake pedal is pressed it goes down then firms up at the bottom as if there is something stopping it from traveling normally

[gensport]

master cylinder dude

[MR-VTEC]

Cheers man