austin944

After replacing the front rotors, pads all around, and front brake lines, I'm trying to bleed the brakes with a Motive power bleeder and I'm getting a soft pedal. I isolated the problem to the left front brake line by blocking off the master cylinder port to that line. When I block off that port, the pedal is fine.

I removed the LF caliper and bench-bled it with a MityVac, knocking it with a soft hammer while bleeding it to get the air out. After re-installing the caliper, I cracked open the brake line at the caliper and depressed the brake pedal a bunch of times to bleed out the excess air from the line, and then I did the normal bleeding with the Motive power bleeder, along with depressing the brake pedal several times. Still no luck.

I can't find any leaks anywhere.

I'm going to try re-building the caliper and bench-bleeding it again, but do you see anything I'm doing wrong, or is there anything else I can try?

Dave951M

Try replacing the hose to the caliper first. An old hose can give a spongy feel to the pedal. Not as much as air in the lines, but absolutely a soft feel. If you replace one hose, it's best to replace all of them. Thinking is, if one is bad, the others can't be far behind, especially when pressure increases because of a new hose on the system. Try at least one hose on that caliper to be certain.

dualblade

wait, are you saying that you opened the line at the caliper and pumped the pedal? if you do this, you will suck air in to the line.

Dave951M

He's using a motive bleeder, no pedal pumping needed.

austin944

Thanks for the quick replies. I pulled the caliper piston out with some difficulty and found some rust in the caliper piston bore, so I'm hoping that's the cause of the soft/low pedal.

Dualblade, I cracked the line just a little such that you have to really press down on the brake pedal to get fluid out. And then I bled again using the power bleeder. My reasoning is that I didn't want to force a lot of excess air from the dry brake lines through the caliper and have to bench bleed it again.

austin944

I replaced the caliper but it didn't fix the soft/low pedal. Before installing the caliper, I bench-bled it with a MityVac and then bled it on the car with a Motive power bleeder.

I think the problem lies in the LF caliper because when I block off the master cylinder port for the LF caliper, the pedal is fine. I moved down the line and blocked off the hose end near the caliper connection, and the pedal is fine there too.

I took the car for a drive, there is nothing unusual except for the soft/low pedal and the car has weak braking as a result. I can't find any leaks.

Any ideas?

Wrecksimple03

i just replaced my pads and rotors all around too, i have the same problem. i powerbled the brakes and no luck...i did this yesterday im going to try and just drive it and see if it gets any better if not, i have no clue

austin944

When you replaced the rotors, did you leave the calipers connected to the brake lines, or did you disconnect the brake lines? If you opened up the brake lines, you probably still have air in the system.

Kevin Baker

Question. Are you guys bleeding ALL of the calipers? RR, LR, RF, LF. I would expect that if you hooked up the power bleeder you would push all the air out.

Zero10

Hmm, I have the same problem, although I haven't isolated it to the front left. Only to the front brakes. After running more than 2 litres of brake fluid through the system, I'm still getting sludge out of the caliper, so I wouldn't be surprised if there was air in there.

tconn

I've had the same problem. It showed up after replacing brake lines rotors and pads. I've changed the master cylinder swapped out the ABS unit with a good used unit and bled the system numerous times. I've power bled it with the
Motive Power bleeder, gravity bled it, gavity bled with all calipers open,
one front one rear open and have had no luck.
The car brakes good the petal is just low and a little spungy.
I've got to the point of just living with it but now that I see others with the same problem............maybe an answer is to be found.

Kevin Baker

tconn, if you are having problems bleeding with abs, you may have air trapped in the abs pump itself. See if you can get the abs system to engage. If there is air in the pump, cycling the pump may get it out.

tconn

Kevin thanks
I was talking to some one at the autox today who had the same problem
and finally nailed it down to the abs unit. After activating it a # of times he was able to get the air out.

austin944

I fixed this problem a long time ago and wanted to follow up and post the solution in this thread which I started.

The fix for the weak brakes and soft pedal was to drive the car, and to bed the pads in with repeated panic stops. I had gotten new front pads and rotors installed, and apparently the brakes were unusually weak as a result. It took a good long time to bed them in -- there were many repeated stops before it felt right.

That would explain the weak brakes but not the soft pedal. For that, I don't have an explanation as to why driving the car fixed the pedal. I read on the e-mail list that sometimes a brake caliper seal can get "stuck" in the wrong position and cause a soft pedal. But I don't really know if that was the cause.

Thanks for all the helpful replies. Hopefully this fix might be useful to someone else.

docwyte

It can definately take some time to bed in pads and rotors. When I first put the pads in my 951, I couldn't activate the ABS. I bedded them in per manufacturer's recommendations, then let the car sit overnight with the e-brake off to let the pads temper. I can now easily invoke the ABS...