Hard Brake Pedal

[PhatSol]

Just noticed today that the brake pedal starts to get really hard under heavy loads. I did a search of course, and there is lots of info on soft pedals but nothing on hard ones... It feels like the booster has run out, but this is impossible since the engine is at high RPM with the thottle shut when it happens (high manifold vacuum). I'm not sure where to start looking. Any Ideas?

By the way, pads are quite new (but have been bedded in properly) and the (stock) rotors check out ok. Pads are EBC greenstuff.

[SiR JDM]

Get it checked, even if people on here are experts, they cannot tell u exactly wats wrong by ur description.. if ur having problems with ur brakes, its not only dangerous to urself but to others on the road.. get it fixed asap..

Sounds like has something to do with ur brake line pressures or ur brake stop..

[PhatSol]

Get it checked, even if people on here are experts, they cannot tell u exactly wats wrong by ur description.. if ur having problems with ur brakes, its not only dangerous to urself but to others on the road.. get it fixed asap..

Sounds like has something to do with ur brake line pressures or ur brake stop..

Yep getting it tested today. I'm told I might have a faulty booster. Just asking on here to see if it's a common EG problem or anything like that. Will definitley be getting any repairs done before working it hard again.

[b18a]

PhatSol// yeah, under a long continueous and hard brake, my brake also become hard. and when engine idle, i can hear the air sucking noise from the brake booster. this is because of the brake booster leakage. i heard there is no fix of it, the only way is to change the whole one.

u may choose to change it with DC2R or Vtir one, remember to tranplant the booster and brake master cylinder together. and u got ultimate stopping power.... hehehe ;) (bigger master cylinder)


Cheers

[PhatSol]

What does the bigger master cylinder do? I am thinking of getting some slotted rotors at the moment. I had the brake fluid changed, and everything checked out ok. Still not quite happy with the feel though compared to other cars I have driven. Looking for ways to improve it. It's like it dosen't have as much power as the Mirage used to (but it is certanily more fade resistant lol)...

[b18a]

What does the bigger master cylinder do? I am thinking of getting some slotted rotors at the moment. I had the brake fluid changed, and everything checked out ok. Still not quite happy with the feel though compared to other cars I have driven. Looking for ways to improve it. It's like it dosen't have as much power as the Mirage used to (but it is certanily more fade resistant lol)...

the bigger master cylinder press the brake fluid faster than the smaller one when u hit the brake. thus, after change a bigger master cylinder, use the same strength u usually hit on the brake, u will feel the brake is more sensitive, and the car is more willing to stop (becareful of wheels lock up)

changing brake fluid or anything else wont fix the problem, brake booster is an individual part.
brake booster is a vacuum booster, which has a pipe links to ur throttle body and there is a one way valve in the middle of it. when engine running, the engine sucks the air out of the booster, so u have power assist when braking. when engine shut off, u may found the brake is getting harder every time u press, and the pin inside the booster that press the master cylinder wont go back to original position.

when hard braking, the workload of the booster is heavier than normal, and if the car is aged, one or some of the rubber seals inside the booster may failure, then leaks air in, partially no power asist, so the brake become hard.
as it's vacuum inside the booster, after u open it to change seals, it's hard to seal it back to totally vacuum as original, so people just find a good condition 2nd hand to replace it.

change a slotted rotor will only make it worse, even heavier workload than before, leak air more seriously. i am using slotted rotors too, the vacuum function failure when i am in track day, the brake was damn hard and scary.

my solution is reverse the one way valve, so there is no power asist anymore, and no sucking noise from booster. brake was hard at the beginning, but after the muscle built up(right leg), it feels damn good. the response of the brake is awesome. and save engine power too.... :D
however, i dont recommend this, u can just replace the booster and master cylinder together. remember, once u change the booster, u must use the master cylinder come with it.


Cheers

[PhatSol]

my solution is reverse the one way valve, so there is no power asist anymore, and no sucking noise from booster. brake was hard at the beginning, but after the muscle built up(right leg), it feels damn good. the response of the brake is awesome. and save engine power too.... :D

Hahaha sounds like fun lol. Nah my brake booster dosen't leak, it's just that my old car had a stronger booster. I think i might look into sourcing the ITR booster and master. Thanks for the info ;)

[b18a]

no worries mate...


Cheers