Very soft pedal after frong disc brake swap

Takt · Jun 30, 2007

Two weeks ago, I used the swap kit from discbrakeswap.com. Everything went smooth, and would recommend.

However, I have a very soft pedal ... goes all the way to the floor before I stop. THe pedal does not pump up ... so no air in the lines. Everything is hooked up correctly and I bench bled the master cylinder per the instructions.

Any suggestions?

mustangman1974 · Jun 30, 2007

there is air in the lines. It took me 4 bottles of brake fluid to get all the air out completely. You most likly have the front done correctly, but the rear drums usually have issues with the bleeders loosening to much during bleeding, therefore letting air back in.

Rusty67 · Jul 1, 2007

Are you sure you got the right/left calipers on the correct side ?

D.Hearne · Jul 1, 2007

New brake hoses or did you reuse the old ones? If the pedal goes to the floor, you've still got air in the lines though.

zookeeper · Jul 1, 2007

Rusty67 said:
Are you sure you got the right/left calipers on the correct side ?

You beat me to it. If the calipers are interchangeable side for side, then swapping them will result in the bleeder being the lowest point in the caliper rather than the highest and you'll never get the air out. Don't ask me how I know this...

Takt · Jul 1, 2007

Thank you for the replies. Just rechecked the car, and the bleeder is on top ... so they were installed on the correct side.

I thought that a brake pedal would "pump up" if there was air in the lines? It doesn't.

I re-used the brake lines with the exception of one from MC to distributor block.

Thanks

D.Hearne · Jul 1, 2007

I was asking about the soft hoses not the hard lines. I recently swapped mastercylinders on the 77 Comet I've been working on. I never bench bled the master, replaced one hard line from there to the distribution block, rebent another to the same location, filled the master reservoirs, set the cap in place. Left it like that for 2 months while working on the rest of the car. When I was ready to test drive it, I got in, pumped the pedal three times and it firmed up then and there. Never bled a drop from the front pistons or rear wheel cylinders. Wish they all went that way. Or had the time to wait..........

Takt · Jul 2, 2007

Thanks again for the reply. The soft hoses from the calipers to the connection in the wheel well came with the kit ... so those are brand new. Everything else was reused.

I had to start the bleeding process by myself ... so a buddy told me that I could fill the MC with fluid, and crack open all four bleeders. Then wait. Gravity would do its thing ... just make sure to check often to air doesn't get into the lines (plus brake fluid is pretty nasty to paint). The rears started squirting fluid almost immediately, the front left (closest to MC) was next ... then I got impatient and had my wife help bleed the front right.

Started with the FR ... then went to all four corners three times.

Now I'm here with a soft pedal. Guess I'll go around a couple more times.

Thanks

zookeeper · Jul 2, 2007

Now you're on the right track. It sometimes takes several laps around the car (for me at least) to bleed brakes, and even then it seems to help if I bleed them again after a drive to get the brakes warm.

D.Hearne · Jul 2, 2007

Bleed em all again, but this time start with the right rear, then left rear, then right front, end with left front. You've done em backwards if I recall correctly.

gsxrken · Jul 2, 2007

Takt said:
Thank you for the replies. Just rechecked the car, and the bleeder is on top ... so they were installed on the correct side.

What the previous posters are warning you about is that the calipers are very tricky. You can have the bleeders "on top" and there is still an air pocket. Look very closely at your calipers once more and make sure the bleeder tapping is at the highest point. I forget now, but I believe you want the bleeder pointed towards the rear of the car. When they are on the wrong side, they are pointed straight up.

If that's not your issue, I do hope you figure it out. You can get into pushrod depth issues if you are going from manual to power and different M/Cs etc...

degins · Jul 2, 2007

gsxrken said:
What the previous posters are warning you about is that the calipers are very tricky. You can have the bleeders "on top" and there is still an air pocket. Look very closely at your calipers once more and make sure the bleeder tapping is at the highest point. I forget now, but I believe you want the bleeder pointed towards the rear of the car. When they are on the wrong side, they are pointed straight up.

If that's not your issue, I do hope you figure it out. You can get into pushrod depth issues if you are going from manual to power and different M/Cs etc...

That's correct, the bleeders should point back and be at the higher mount point.

Don't rule out improperly adjusted rear brakes.

HHStang · Jul 3, 2007

swapped from what?

Many folks swap later model calipers that don't put the bleeder at the very top, or high point on the car. When I did mine, I had to take the calipers off, and hold them vertical to bleed them. (put a board or something to keep pistons from closing in). The bleeders looked to be at the top, but really weren't.

Try clamping the soft lines going into each caliper individually and see if the pedal gets hard. If it does, you've probably found where your air pocket is.

Good luck!

Very soft pedal after frong disc brake swap

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