Brake pedal problem
 

I wanted to pick your guys' brain about a strange brake pedal problem i've been having for a couple weeks now.
Everytime I step on the brakes, the pedal drops at least 2 inches before I feel the car starting to slow down. Even then the brake pedal isn't as firm as it used to be. If it quickly pump it once, release, and then depress the pedal again, it's stiff (normal) right from the start.

If it take a turn quickly, the pedal drops even more (2-3 inches) before the car starts to slow down.

- Brake fluid level is normal
- Brake pad wear is normal at 50-60% after 18k miles
- Rear brakes seem to be doing more work than the fronts based on radiated heat after medium stops.
- No strange vibrations

Nissan says it's all normal but can't explain why it changed all of a sudden. Has anyone had this problem before? Does it sound like I need to bleed the lines?

bleed em. if that doesn't work make sure your master or slave cylinders aren't leaking internally.

it could be your master cylinder. but if you can pump the brakes and get better results, that sounds like there is something wrong with the pressure in the lines or brake booster not working correctly. trying to recall knowledge here, i believe power brakes have an internal device that creates suction while the car is driven, preventing the pressure from staying in the lines, therefore preventing the brakes from clamping unless you hit the pedal, decreasing volume in the cylinder and forcing the fluid into the lines. so you may not have enough fluid to pressurize the system, check that out. anyway im no expert, this sounds like something you should take to your dealer soon. you dont want to end up with them cutting out completely one day and causing u to wreck.

Thanks guys i'll try bleeding it this weekend. I too was worried about it so I brought it down to Power Nissan but they said it's normal...

Sounds like it could be pad knockback according to your description that it's more pronounced after cornering:

http://www.stoptech.com/whitepapers/knockback.htm

I would suggest finding a long, straight road where you can do several heavy-braking slowdows in a row, with a fairly lengthy acceleration time between each one. If each of these stops gives you a fairly solid pedal, and your problem really only happens after cornering, that might help you cross off pressure or other problems with the master cylinder.

Good luck!

Thanks for that link Gary, it definitely describes what I am feeling. I just realized today that making quick U-turns makes the pedal drop very apparent. It drops enough that even a Nissan certified tech might finally agree with me.

My question is why I'm getting this on the street. Yes I do corner quickly but it shouldn't be enough to trigger knockback. Perhaps I need to go tug on the tops of my tires before I commute home!

HanZolo,
Take this serious, and insist the dealer (or independent) take it serious also.
What is the only system on your car that MUST work every time, the one system that can kill....BRAKES.
A slow degredation in performance can be dealt with. Unpredictable performance is unacceptable.

Just wanted to update this for the archives. I measured my rotor thickness today with my new fancy micrometer and the front rotors are only 29.4mm thick. They are 33mm thick when new and the wear limit is 30mm. I haven't measured the rears yet but i'm sure they are below the limit also.

**Edit: n/m, i'm back to square 1. The re-read the specs and it's 30mm new and 28.4 replace.

HanZolo:

It doesn't sound normal to me.

You might want to have American Tire & Brake take a look at them.
They work on Mercedes, BMWs, Porches and XCrossers.

This is an independent shop, not affiliated with Discount and America Tire.

They are in Mission Viejo at 23652 Via Fabricante. Phone 949-830-0760. They are at Alicia Pkwy and Jeronimo.

They have aligned my car twice and it has held well. They do not agree with Nissan's settings.

I also had Hawks HPS installed by them all the way around 8,000 miles ago.

They are professional and know what they are doing!