Mushy brake pedal after swapping my front brake pads
 

While I was compressing the caliper on the 2nd side of the swap, about 5 ounces of brake fluid was forced out of the resevoir even with the cap closed. Now my pedal is mushier then normal although it's still driveable and doesn't sink to the floor.

Reading online some have said this could have damaged the master cylinder or brake booster? :dunno:

The first thought with the mushy pedal is air in the system but is that possible considering all I did was swap the pads?

I can firm up the pedal to a normal feel with a pump or two but then it goes back to the mushier feel.

Doh! Anyone experience anything similar to this? I'm gonna try bleeding on Friday but is there another way to tell if I damaged anything else?

Thanks in advance

It behaves like it has air in it.

I don't know if it is possible to damage the system this way. 5 ounces seems like a ton of fluid due to compressing the piston to get new pads on. Maybe your estimate is off...

I would start with a proper bleed and see how it goes.

Normally you would open the bleed nipple to allow fluid removal when pushing the pistons back to accommodate new pads, rather than pushing the fluid all the way back up to the reservoir. But that usually works too, as long as you remove some fluid from the reservoir first.

And yeah, it sounds like there is air in there somewhere, although I cannot see how. Are you sure the new pads aren't hanging up on something? I guess that would reduce the braking force but it might explain the spongy feel.

Bleeding the system should be the first step and go from there.

:iagree:
Brakes should be bled (Replacing all the old fluid) with new fluid every 2-4 years, as this stuff absorbs water from the atmosphere which reduces the effectiveness of the brakes to the point where one hard stop will heat up the caliper/fluid to the point of boiling the water and will lock one or more calipers (NOT A GOOD FEELING). Any good silicone DOT 3-4 brand name will work. EXAMPLE: Valvoline DOT 3 and 4 Synthetic Brake Fluid (32 oz.) 601458: Advance Auto Parts
There is a posting that shows who manufacturers what brand name fluid on this site. If the operations of your brakes is not a factor then think of all the rust that is building up in the system as more and more water gets in there.

DISCLAIMER: yes, people drive cars every day without ever bleeding the brakes system and experience no issues as long as they owned the car. Yes, the fluid is dirty, yes it contains water, yes the system is compromised more and more as time goes on, but they don't see it or feel it so it must not be happening. This is often referred to as the ticking time bomb of deferred maintenance costs.

Process:
Bleed the brakes in the normal fashion RR, LR, RF, LF (All positions are as if you are sitting behind the wheel). I personally would recommend a power bleeder but it can be accomplished with a volunteer who understands basic commands like "Down" - meaning push on pedal until it bottoms out - there this no need to mash the petal, just a firm push will do. "UP" means release and do not touch the brake pedal until you have closed the bleeder screw on the caliper. 9-29 pedal pushes will move most of the old fluid through the system and out the Right rear. The fluid will turn clearer.

The Power method is much better as you are creating pressure at the master CYL with fluid pressure that moves all the junk out of the complete system. Plan on 1-2 hrs or a whole lot less of you have done this before. See online Vids of the process.

CAUTION: MAKE SURE THE MASTER STAYS FULL OF CLEAN NEW FLUID, during the process. Otherwise you run the risk of injecting air into the system and your troubles will magnify.

Oh, and find someone who knows cars unlike my helpful wife who was pushing on the gas pedal while talking on her cell phone and yelling "there is no resistance all all" as I rolled around looking for the complete split in one of the hoses. Note to helper: the brake pedal is the fat one that goes L-R not the skinny one that goes up and down. :rofl:

Great post Stephen, however the bleeding sequence you stated is a thing of the past. This was the way to bleed, back when cars had a single valve master. On all of our e53's it doesn't matter which wheel you start with. :thumbup:

I think the biggest piece in our brake systems is the ABS block as it must hold 6 oz of fluid by it self. My only recommendation for doing the RR, then LR is start with the longest brake lines first as each one will seem "faster" as you get closer to the master. You are correct there are separate lines per wheel from the ABS junction back.

Tips: Suck all of the old fluid from the master FIRST, then refill. This way you will be pushing only clean fluid through the system. Smack each caliper with a hard plastic mallet on the last flush of each wheel as it will release any air pocket/bubble clinging. Also think about rebuilding each caliper (it is just a dust boot and a sealing O'ring on the piston) if you have more the 100K. This will allow you to remove all the crud build up at the caliper. The process is simple and only requires shop air and a block of wood to catch the piston when you "pop" it free of the caliper.
Paint the calipers the color of your choice: Yes, Pink is available

Cool.

I wouldn't recommend removing fluid either as this could bring in air. You get air in the abs pump and you will have to use software to bleed.

For the record I'll be helping bleed this X on Friday with INPA so we can be sure all the air is out.

please post procedure on how you bleed with INPA. Thanks.

No prob slick. I'm sure one of us will be posting the final results and maybe I'll write up a diy on bleeding with INPA.

If your itching now, there are a few utube vids on the procedure. Not sure if there is one specifically for the e53...

Good to see lots of copper anti-seize in there, Stephen. I use this stuff everywhere too! :thumbup:

http://www.crc.co.nz/ImagesCust/imag...940876ad54.jpg