OK so I searched for this problem. I found another thread that stated this exact same problem but in never ended with a resolution. I think that was kind of funny because the OP complain he found a thread that never posted a resolution so he didnt know what to do. http://my350z.com/forum/brakes-and-s...ake-pedal.html

Car: 04.5 350Z Enthusiust with 65,000 miles.
Mods: Slotted Rotors (belive they are StopTech but where on car when I bought it few years ago), newer HP Plus pads, Kenetix SSV manifold, Injen short ram, Fidanza 3.2 clutch, Nismo Flywheel, Full suspension.

Problem: Sunday I went to the AutoX. Temps where almost coldest of the year, mid 40's. The day was going great. First time out on my new Bridgestone RE-11s. First 4 morning runs went great. Then the afternoon, 1st run I was killing it. I was topping out 2nd, hit the rev limiter a couple time (on purpose, to prevent up shifting & down shifting for a split second) then coming up to last hard right to exit the course I stab the brakes but all I had was a hard pedal. May have been normal pedal travel but no real braking. Ruined the run. Next run went fine. 3rd and final afternoon run exact same thing happened! Let off, reapplied, let off, reapplied, let off, pressed hard as I could. Pulled hand brake to slow me down. Then they worked fine again. Havent notice anymore problems.

 

Any updates to this problem?

Something similar happened to me this morning. Drove the car for about 30 mins, normal street driving. Forgot to grab something at my house, so I rushed back. Long stretch of road I hit about 80-90, tried to brake and felt hard pedal. The car hardly slowed at all, I almost ran a red light because I couldnt stop! Haven't tried another 90 to 0 stop yet, but drove the rest of the day & it seems fine.

OEM Brembo's with Hawk pads with about 2,000 miles on them.

Can't really think what it could be....guessing improper temperature or glaze on pads??

 

Have you done a brake booster check?

 

Hmm, no but I'll look into it. Thanks!

 

I would definitely check your brake master cylinder and fluid. I've been using Hawk HPS pads for several years with DBA slotted/drilled rotors and never experienced what you're describing. If you guys follow thru and find a solution post it on this thread so we'll finally have an answer for future questions about "hard brake pedal."
Gary

 

Question for you members having this Hard Pedal issue, did you do the "Bed In" process right after installing your HAWK pads? SEARCH This coats your rotors so you won't have hot spots, lengthens pad life and eliminates brake noise....it's magic!
Gary

 

I have a completely stock brake system. I'm having this "hard pedal" and it's actually quite frightening. I've practically rolled half way into a busy street several times recently because I couldn't stop, and I had my foot down like my life depended on it (IT DID). If for any reason I have to slam on my brakes in an emergency, it's not gunna happen! I can't stop for ****, and I have to keep a good distance behind somebody. If I try to stop slowly, and slowly increase pressure, I'm fine, but I feel as if the brakes aren't grabbing like they should. Rotors and pads are fine, and no ABS light.

 

Brought my car back into the shop where I just got my JWT clutch, flywheel, etc installed, because that was only a few days ago..

While the engine is running, pop the hood and have someone depress the brake pedal in and out. When listening over the drivers' side firewall where the brake booster is located, I have a hissing sound (vacuum leak), and you may as well. Something to check.. The brake booster basically has an inner tube that can develop an internal leak.

New brake booster from Rockauto: $342.29

NOT saying this is the guaranteed fix, so don't shoot me if it isn't, but this is the route I'm taking soon.

 

Generally a hard pedal is a brake booster problem/vacuum leak. It's why I suggested it in May.

 

I saw where you suggested to do a brake booster check, is that a universal concept, or is there a certain way to do it for our car?

 

Here is the procedure from the 2004.5 FSM, but it's fairly universal.

 

That would be what's wrong.. Thank you. I saw the same procedure in my 2006 Sedan brake section. I will post back after I get it replaced.