I just changed all four of my pads. For those of you who have done this before, when you take the old pad out and put the new pad in, you have to compress the piston inside to make enough room for the new pad. Well, I did that for the fronts first and it was no biggie. For the rear though, when compressing the piston, I could hear fluid squirting out of the brake fluid reservoir. When I went to look at it, the fluid was overflowing everytime I compress the piston. I just put a towel over the reservoir and finished the rest of the pads.

Now, I start my car and pump the brakes a couple times to get thee fluid flowing, but the pedal isn't as stiff as it should be. I can press it down to the floor with little resistance. The fluid in the reservoir did not go back down either after pumping the brakes many times. I then pumped a little of the brake fluid out, so the level would go back to the max fill line. Still, the pedal felt way too weak. So, what do I do to make the pedal travel the way it used to be? Did I do something wrong?

Btw, I have oem Brembo's. And I did not change or touch the brake lines.

 

You should always bleed the brakes after replacing the pads. Sounds like you have some air in the system. If it where me, I would fully replace all the fluid when you change the pads since brake fluid likes to absorb water and that lowers the boiling point of it.

Next time check the reservior before starting each set of calipers to see if it is going to overflow and take some fluid out if you think it is. This didn't cause your problem, it just makes a mess.

 

+1

It's also good practice to open the bleed valves when pushing the pistons back in the caliper. It's easier, won't push sood and contaminated fluid in the ABS system, prevent fluid overflow in the reservoir and it garantee you'll get clean fluid in the caliper.

As it is, you need a serious bleed.

One more thing to remember. New pads do not mate perfectly to your rotors. That's normal. Don't try any hard braking for the next 200 miles or so, while the pads wear down and start to make contact on their whole surface. Then you'll have a stiff pedal and maximum brake torque.

Before that happens, part of the sponginess commes from the pad bending under the pressure.

Again, no hard braking rigth away! You'll be using a fraction of the pads, this will generate tons of heat locally, might heat treat you rotor and lead to brake shudder...

 

Brake tests are specified with pedal pounds vs deceleration in 0.00G
Something like 22 pounds yields 0.85G deceleration at 60 mph with pads beginning at 120F..........graph vs pad temperature vs speed vs pedal pressure.............SOFT is so inprecise!

If brake fluid ever boils [even once] it must be replaced because the chemical structure CHANGES from the temperature reacting with the absorbed moisture creating an acid...........which attacks the o rings. The higher the moisture content the more turns to acid.

 

Wow, thats useful.

+1 for Kolia

To the OP, what pads are you using? Some compounds are softer than others (compress more) and can give you an totally different feel.

Chris

 

What about the bed in procedure that some manufacturers tell you to do? For example, 5 moderate stops from 35 and 3 hard stops from 50.

Btw, I am using Project Mu B-Force pads. Next time I will open the bleed valve, but I don't know how air/water got into the system. It should be fine. The car still brakes, the pedal just doesn't feel as stiff as it should be.

 

Edit - Found a good DIY on stoptech's website for bleeding (not a full flush), so I am going to try that and see if it helps.

 

Follow the manufacturer's recommandations. Braking from 50 mph isn't very demanding for a high performance pad. Just don't do 6-7 run from 80+mph right after mounting the pads!

From Q45's post, the water can come from the fluid itself once it has boiled.

Just aging will decompose the fluid.

 

Ya I understand that, but the brakes worked fine before I changed the pads. I'm going to try bleeding each brake for a second or two to see if that fixes it.