Ive been having problems with my brakes lately, and am not sure if this is a common problem or if it is just me. Lately for the past year or so, I have noticed my brakes are not up to par as they use to me, and this happen after I switched over to brembo sloted and drilled brake rotors, HP Hawk brake pads, and just recently replaced my brake master cylider. I find my pedel to be a bit mushy, and have to double pump and sometimes have to use my ebrake to come to a resonable stop at high freeway speeds. I have gotten really go at doing so as well, however, I do not think this is the kind of brake performance I expect from my FD. Basically I want a stiffer brake pedal, which my car has been lacking. I have been suggested the possibility of adding an additional brake booster and even read about people upgrading to the 929 master cylider, however, I do not believe that should be nessesary since my brakes were fine before. I have bleed my brakes many times, replaced the master cylinder, and still find the brakes a bit mushy, unless double pumped. Changing the brake lines imo would not help his problem and I am running out of ideas on what could possibly cause this problem. I have not found any leaks, and do not think I have any air in my brake system, since I have bleed them to death. Besides that, I have never had my ABS kick in under hard braking as well. Yet they ABS light never comes on to signal there are any problems with my ABS as well. Anyone else have this problem or is it just me? what could cause my braking system to be working so poorly, or is it I am just asking too much from it? I have replaced everything except the brake lines itself which seem to be still in good condition, so what else could it be?

 

You have the HP+ pads? They may need to be warmed up before working correctly. The HPS is a better pad for hiway or street driving without constant braking.

If you have had your pads of a while, maybe the pads are wearing thin.

Are you bleeding your brakes properly and getting all the air out?

 

Marvin,

I've got a couple of questions/suggestions:

What exactly do you mean by "double pump"? Do you mean that you have to step on the brake, lift off your foot, then reapply the brake?

It could be a hydraulic problem due to the fact that it is affecting your brake pedal (forcing you to double pump the pedal).

Are you still running the stock calipers?
Any signs of brake fluid on the ground?
Do you notice your brake fluid level (in the reservoir) to be decreasing?
Any signs of brake fluid leaking from the master cylinder (like dripping slowly off of it)?

Inspect the brake lines. It may have a small leak/crack in them which allows air to enter the lines over time.

Did you replace the slave cylinder? (You mentioned that you replaced the master).

Also, did you follow break-in procedure when you first install the brake pads? If not, then you could've scorched the surface/material of your brake pads, which lead to reduced stopping distances.

You're right that upgrading the 929 master cylinder will not help your situation. You say that you bled the brake lines, so I'm going to assume that it was done correctly.

Are you driving your FD right now (as your daily driver)? If I have time, I'll swing on by to see if I can help you, but it will more than likely have to be on Saturday or Sunday. Let me know.

You still have my number right?

 

Only slave on an FD is the clutch, it don't got drum brakes!

This could leave the pads with little bite, but wouldn't cause a mushy pedal.

Did the mushy brakes start before or after you replaced the master cylinder? A mushy pedal is strictly a hydraulic problem and the fact that it gets firm with a double pump tells me there is air or water in the brake system. Brake fluid collects moisture from the air which leads to mushiness over time, that's why it should be completely flushed and changed on occasion.

You say you cannot lock up the brakes by pushing the pedal? Does it go to the floor and then you pump it again to get braking? Even with pumping you cannot trigger the ABS no matter what? Can you lock the tires?

When you replaced the master did you bench bleed it first? The master itself must be bled before installation as it is impossible to get the air out of it by bleeding from the calipers.



bench bleeding master cylinder

 

HP+ need to warm up, they get cold on regular driving, but for autocross, once they warmed up, they bite like crocodile.

we also found out that bleeding once is not enough. you need to at least bled the system twice.

Use ATE or Motul.

reza

 

DamonB: Thanks for the correction. Upon reflection, I agree that it is a hydraulic issue rather than the pads.

 

ive bleed the whole system atleast 3 times, Tripoint has bleed them atleast 2 times and checked my lines as well, and even the freakin dealer has bleed the whole system 4 times. My pads are around a year old, and when I replaced them, I got new rotors with them as well, so resurfacing them is not an issue. Both Tripoint and my dealer thought it was the Master cylinder, which I just replaced 4 days ago, and I still have this problem. There are no visible signs of leaking anywhere since, unless it was internal, which is why I replaced the Master cylinder, and my lines are fine. It sure feels like there is air in the system, however, it has been bleed so many times by so many people, I doubt it is that.

 

But who replaced the master cylinder? Was it in fact bench bled before installation?

Rotors, pads etc have absolutely nothing to do with this problem.

 

If you have the stock brake hoses try "pinching" them off, you can use vice grips ( let the lectures begin) just be smart as it doesn't take much pressure. (Don't do this with metal braided or teflon lines.) Do all if possible or at least in pairs. If that makes the pedel better than you know the problem is at the wheels.
You didn't say anything about a vibration so the rotors should be ok, but warped or rotors with thickness varations can cause this. Brake pads that have broken down and are being compressed, it's not common but I've seen it. If bad enough to cause a low pedel you should be able to see the pad materal compress when someone pushes on the pedel. Caliper problems, bad seals, sticking pistons, pads that don't fit properly, and of course air.
If pinching off the hoses doesn't work it could be master cyl., the abs unit or of course air. The abs unit has a resivour to hold fluid during an abs event, if the dump valves are leaking than you basicly have a controled leak within the unit. Vary rare but possible. The only way I know to test the master cly is to make plugs to replace the brake lines to isolate it from the system.
Good luck, I think you will find that pinching off the hoses will make the pedel much better and help isolate the problem. Jeff

 

I've never experienced this in my two years with HP+ pads. HP+'s have great cold-bite. And then, they get a little better when up to temp. But cold-bite won't have any effects on pedal feel.

The mushy pedal feel sounds like there is air in the lines somewhere. Crashunit, when you say you bled the entire system, do mean you bled each line for an extended period of time? How did you know when the entire system was flushed? How was the brake fluid flow when you bled the lines .... bubbly and fast or steady and slow? There is the possibility that your bleeder valves are letting air into the system ... I have that problem, but I just use disc brake grease to seal the bleeder valves when I bleed the system. Messy, but effective.