p1fcl01

Followed diy on brake pad change. Everything went well, no brake oil drip afterward, no squeaking nosie at all. What should the brake pedal feel should be? The pedal still feels low and not firm like other new brakes, use Akebono ProAct. The braking power does not feel super at all. I am just curious if I've done anything wrong or that the way it should feel.

Thanks

Frankie

p.s. Thanks to the diy oil was also change with no hassle....

Super thanks to Lexmex!!!!!!

TunedRX300

Did you bleed the brake fluid?

p1fcl01

Yes, not all but some (just enough so it does not overflow when pushing the piston) and refill afterwards, but it was less then what I took out, just a little less.

TunedRX300

In order to make brake bluid an imcompressional medium, you must bleed all air out from bleeder valves on brake calipers. Make sure you bled all four brakes until no bubbles are seen.

Lexmex

Thank you. Also give a thanks to TunedRX300. He was the one convinced me to get the Akebonos and I consider him the brake master of the RX300 world.

TunedRX300

Not really. I just happened not afraid to get my hands dirty couple of time working on the brakes and share my experience with the forum. Other members such as Salim also knows a lot, I pick up a lot from them also.

Lexmex

That's true...Salim did make several important comments when I did my brake pads DIY

mschluns

Why would the brakes lines need to be bled, if the lines were not broken into there would be no air to enter them, when installing the new brake pads the caliper pistons need to be pushed back into there home position, i use a c clamp to easy them back. no way for air to get into the system unless u have a leak or u disconnected the brake line.

salimshah

We all learn from each other. I am ready for brakes 110.

Salim

salimshah

There might have been air before the pads got replaced. With the new pads travel does not change (amount of pumped fluid to make the pads travel is the sames).

Salim


Super thanks to Lexmex!!!!!!

TunedRX300

Brake system is not air tight, for example, rubber lines have pores and the mater cylinder cap can not seal 100% air out. When one services the brake and adds fluid, the brake system is opened and exposed to the air by definition.
Brake fluid by design attracts water over time even left unopened, which lower the wet boiling temperature. When fluid boils, bubbles form. Nearly every automotive manufacturer stores their bulk brake fluid in large containers which are subjected to a constant VACUUM. Very expensive but very necessary.

p1fcl01

So there is really no way to tell if I have air in the line unless I go and bleed all 4 brakes, even if I only worked on the front pair, right? All I can tell is that the brake pedal feels about the same as before I replaced the new pads and the old pads were pretty worn out.
If so, I'll get started this weekend. Thanks all.....

Francis

I just changed my rear brake (oem) pad 2 weeks ago. I did not disconnect brake line or open the brake cap. I only used c clamp like MSCHLUNS did. The braking prower is better now.

I did make mistake when I changed brake pad with my 01' 330i. I opened the brake cap when I was doing that. And some fliud was overflow while I c clamp the pistons. I felt weak on braking power, a lot of air got inside. Then I bled the brake lines and the braking power came back.

p1fcl01

Now I am more confused Am I to not open the brake cap next time I change the pads only? And only open the brake cap if I was going to bleed the fluid at the same time? Wouldn't the brake fluid come out even the brake cap is close while you reset the brake caliper cyclinder?

salimshah

I hope I do not add to your confusion ...

The fluid is supposed to be free of compressable fluid from the back of the piston(s) to the master cylender piston. The reservoir is above the master cylender piston.

When you press the pedal the reservoir is mecahnically sealed off and pressure is built in the line and thus causing the pistons in the brakes to move. Volume of the fluid remains the same (if it si free from cpomressabile medium) and the mecahnical addvantage (travel of foot pedal) vs the travel of all the pads gives you the leverage. When you disegage the brake the the pressure is releaved and the run out (side to side vibration) of the wheel push the fluid back up the reservoir. As the brake pad wear down not all the fluid is returned to the reservoir.[you observe fluid level falling]. You may have topped it up over time.

When you install the new pads, you most probably pushed the pistons in by c-clamp. This will cause the the fluid level to increase in the reservoir. If you do not remove the fluid then it will spill over.

At all times, your intention should be not to introduce air in the fluid between the pistons and the master cylender. So if you open anything (like the bleed nipple) it can introduce air [only if you push the cylender back] or let some how drop the pressure in the line while the bleeder is opne (release stroke of the pedal).

Unintential introduction of compressabile fluid: Over time your fluid in the reservoir is expsosed to mositure in the air. Water molecules get in the fluid. Water is still incompressabile but when the brakes heat up, you get to boiling point of the water real quick and once the steam is formed you get compressabile medium in the fluid. If you reach boiling point of the fluid even then you loose pressure [that is why brake fluid poil point is high]. Pistons are also not totally fool proof. As the keep moving out, the cyleder walls introduce junk.

It is worth while to purge the old fluid out. It is part of regualr maintenance. The process is similar to bleeding but you get your work done lot quicker.

Hope this helps.

Salim