Brake pedal goes soft after pad replacement

[Doc]

Happy new year guys!

I swapped out the front pads in the 80 this afternoon and the test drive afterwards was 'funky'.

The pedal seems really soft. REALLY soft. IN fact, if I stand on it I can push it all the way to the floor now.
Previously- It would 'lock' and feel like pushing on a brick wall.

The only thing that has changed is that I put new front pads on,

Ideas?

Also, brake MC is very full of fluid now (pushed some out as I was pushing the pistons back in) could that be the issue?

 

[CycloSteve]

Did you crack the bleeders during the install? If so, you will need to bleed. In any case, you may want to flush and bleed the system, if the fluid has not been changed in a few years. Mine was seriously nasty, and went through a quart getting the whole system properly bled. Worlds of a difference.



Steve

 

[Michael Hanson]

I think you got air into the system. Second on bleeding the system. MIke

 

[landtank]

I've found that the brakes can be mushy after a pad install until the pads seat against the rotor square with the caliper. Once they wear true the sponge is gone.

 

[KKAAAR]

Just had the same problem.. I would stop and sit at a light and the pedal slowly goes down with out me putting any more pressure.. Change the mastercylinder and bled it using vacuum(using a compressor) and everything was fine..

I also looked at the brake lines and from what it looks like, gravity bleeding will not work as well as vacuum.. I see a few lines going upwards which the air stops the fluid from flowing..

 

[pdxeod]

I would also suspect air in the lines. But I have not been impressed with the cheap automatic bleaders. The rubber pieces that come with them have not sealed very well. If you have the time, find a buddy and do a good 2 man bleed. The functioning of the brake pedal during the process should seat the pads and calipers. Just watch the level of break fluid very closely.

 

[Doc]

I refuse to believe that by simply pulling the pads and installing new pads that I ruined the MC.

How does swapping pads introduce air into the system?

I'm not trying to sound like a dick, but the problem has to be something simple. I opened no lines, and the brakes were fine before the swappage. Pressure, travel, all good.

Landtanks reasoning sounds possible, I really hope that's all it is.

 

[Doc]

To be clear, even though the pedal is soft, I get great power and stopping, it's just mooshy.

 

[Rob80vx]

If all you did is swap the pads then they just need to bed in and you should feel the pedal come back to how it felt before.

 

[ppc]

If some of the following possibly happened...

Once the brake pedal moves beyond the normal distance there is a good chance that the seals in the master cylinder were damaged. The older and more contaminated the fluid the better chance this has happened.

How did this happen? Pushing the pistons back into the caliper you may have pushed them to the point when everything was reassembled the first push of the petal may have gone down to the floor before the pads made contact to the discs. It is better to make small pumps of the pedal until the new pads make contact.

If the pedal does not gradually sink towards the floor as you continue with constant pressure on the pedal then the MC is more than likely OK. Then I would look for leaks around each piston or bulges in the rubber brake lines.

In any even I would bleed the brakes as the first action.

In the future it is better to crack open the bleeder as you push the pistons back as using the method you have described pushes dirty contaminated fluid back into the MC or ABS controller if so equipped.

 

[86tuning]

I've found that the brakes can be mushy after a pad install until the pads seat against the rotor square with the caliper. Once they wear true the sponge is gone.

Especially if there is a wear ridge on the rotors. A few moderate stops at highway speeds and they should be bedded in.

X2 on not forcing old fluid back up the brake hoses. I'd always do a quick bleed and change a bit of fluid with any caliper service or pad change.

Keep us posted on what you find

 

[mystican]

what is the bleed sequence for the 80 series?

 

[KKAAAR]

I believe you start from the furthest from the MC.. RR RL FR FL

 

[landtank]

I always do RR, LR, LSPV, FR, FL and go around twice.

 

[Doc]

Great info ppc, I'll double check that when I get back to the truck

 

[C6H12O6]

You might also have lost some fluid when you pushed the calipers open to get the new pads in. If the MC was full with the old pads, it might have been over-full with the new pads and spilled a little out during the install without you noticing. Check the fluid level if you haven't already.

 

[CO_Hunter]

Sorry, but a few moderate stops at highway speeds does not properly bed brakes but it may help with the ridge issue and the old rotors. Bedding has been covered many times. Here is an informative link for your reading, one of many. I don't know if this is your entire problem but may be part of it.

Instructions for bedding in your brakes

I first learned about proper brake bedding, many years ago, preparing my heavily modified '65 mustang for running road courses and autocrossing.

 

[Doc]

Update on the problem.

I went away on buisness for a week and recently drove the cruiser again- brakes are back to the way they were (without the squealing). Firm pedal, propper travel.

 

[mystican]

That's weird what happened. What do think was the reason?

 

[VTrocker]

This happened to me as well, about a month ago... Replaced pads at all 4 corners by way of gently pushing back calipers.... And no brake pedal. Pumped pedal for what seemed like
Forever... Nothing. Posted on the forum... Lots of "air in the lines" when the MC was never opened. Thought i had blown out seals in the MC, and reluctantly ordered a remaned unit. Next day, pedal back. Been great since. Toyota gray magic?