Brake Pedal to the Floor!

[V3ST]

Hey guys, I'm trying to chase down an issue with my brakes, maybe someone has come across this.

I've replaced the brakes up front (rotors, pads) and back (shoes, cylinders) on my 88 carbed festiva. I don't get much (if any) resistance when pushing on the brake pedal, both before and after bleeding the brakes all around. Brake fluid was definitely moving through the lines and all the bubbles were cleared out.

I read that the master brake cylinder may have been the issue but after replacing this (new part), still get no resistance on the brake pedal. I bench bled the master brake cylinder before putting it on and also bled it on the car.

I don't see any leaks and the fluid in the reservoir is not dropping. When the car is running, there might even be less resistance than when its turned off.

So I'm thinking its the brake booster? or maybe a vacuum line issue connecting with the booster? Could it be the proportioning valve (doesn't look any leaks there either)?

Anyone know how to narrow down what could be causing this?

Thanks!

[Icedawg]

How did it work before you did the brake job? If it was working then it seems unlikely one of these things just happened to fail. But if you did the brake job because it had this problem then it could be what you suspect now.
If it was working, then perhaps the rear drums are not adjusted tightly enough, so they never produce a resistance?
Or you may still have air in the lines, that can happen even with a decent bleed. Sometime you have to bleed very aggressively.

[TominMO]

No leaks + no fluid drop + no resistance = air in lines, somewhere. Those rear drums can often be hard to get on, as there is little play between the shoes and drum; so I don't think you could adjust the rear brakes loosely enough to have a soft pedal. Air in lines.

[bravekozak]

Festivas must be cross bled, due to the way the proportioning valve works.

Right rear, left front, left rear, right front.

You should have resistance without the engine running or vacuum booster.

[Icedawg]

Tomino is right about how tight the drum fits over new brake shoes, so it is probably air. Even with a lot of air, if you pump the pedal many times very quickly you should get pressure build up, to test for this.
I changed the brake master in my RX7 once, with the help of a professional mechanic, and even with a bench bleed, we spent well over an hour, aggressively bleeding it before we got out the last bit of air. Went through several cans of fluid. After 45 minutes I was thinking the master must be bad, but eventually we got it.

[WmWatt]

Did you gravity bleed or pump the pedal? I gravity bleed with a length of clear plastic hose over the nipple and catch the bleedout in a container to recirculate during the process. You let the fluid run out until no more bubbles appear in the clear hose. Just don't let the reservoir run dry 'cause that lets air into the system Usually to get the fluid to start flowing I have to suck on the end of the hose to creat some negative pressure. You can gravity bleed solo.

[V3ST]

Thanks for your input guys.

I did the brake work because the front pads and rotors were totally shot and this issue with the brake pedal happened while I was turning across oncoming traffic (that was not fun). So, there was this no resistance issue before I did anything.

I followed the haynes manual procedure (same as bravekozak mentions), which at the time I thought was strange, but I later read about the proportioning valve. I pump bled, with the tube on the bleeder valve running into a bottle submerged in brake fluid. I made sure the reservoir stayed full.

When I changed the rear cylinders and shoes, it was very very difficult to get the original drums back on. I never did get them to fit on without any resistance, and when I turn them by hand, they still drag mid rotation. I thought this as because the shoes are larger than the old ones and the drum may not be perfectly round. In another post, someone suggested the parts guys sold me the wrong cylinder (or maybe the aftermarket manufacture didn't have the exact same specs as ford). They looked like the same size as the old ones to me when I put them on.

TominMO, are you saying that because the rear shoes are so tight, there couldn't be enough travel in the shoes to account for the lack of resistance?

Sounds like I will try quickly pump the pedal and see if any pressure builds up, if not, back to bleeding. . .

Thanks guys.

[TominMO]

Thanks for your input guys.

I did the brake work because the front pads and rotors were totally shot and this issue with the brake pedal happened while I was turning across oncoming traffic (that was not fun). So, there was this no resistance issue before I did anything.

I followed the haynes manual procedure (same as bravekozak mentions), which at the time I thought was strange, but I later read about the proportioning valve. I pump bled, with the tube on the bleeder valve running into a bottle submerged in brake fluid. I made sure the reservoir stayed full.

When I changed the rear cylinders and shoes, it was very very difficult to get the original drums back on. I never did get them to fit on without any resistance, and when I turn them by hand, they still drag mid rotation. I thought this as because the shoes are larger than the old ones and the drum may not be perfectly round. In another post, someone suggested the parts guys sold me the wrong cylinder (or maybe the aftermarket manufacture didn't have the exact same specs as ford). They looked like the same size as the old ones to me when I put them on.

TominMO, are you saying that because the rear shoes are so tight, there couldn't be enough travel in the shoes to account for the lack of resistance?

Sounds like I will try quickly pump the pedal and see if any pressure builds up, if not, back to bleeding. . .

Thanks guys.

Correct. And when putting the drum on, especially with new shoes, it is necessary to back off the adjuster as much as possible. You will probably still have to play with how high or low the shoes are, in order to mount the drum. You have to sort of "align" the shoes into a circle.

[jfd64]

I have had an issue like this before when the power brake booster went out.

[ryanprins13]

Most likely air in the brake lines still. If you pump the brake pedal a whole bunch when the car is off does it build up pressure?


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[V3ST]

Most likely air in the brake lines still. If you pump the brake pedal a whole bunch when the car is off does it build up pressure?


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No, doesn't seem to be any build up, I can hear a wheezing sound coming from the master break cylinder / booster when I pump the pedal. I won't have a chance to bleed the brakes till next weekend unfortunately, thanks for everyone's input. I would really prefer not to have to replace the booster, so fingers crossed.

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[Icedawg]

You describe the first loss of pressure happening when you had the old brakes in. If the pads were badly worn up front the piston in the caliper may have come out too far, and damaged the seal when it was pushed back in for the new pads. A leak from the caliper piston will be hard to see without taking the brakes apart again. If you can't build up a pressure by pumping then a leak from a caliper piston or the rear cylinder (assuming a similar problem) may be the source.

[V3ST]

You describe the first loss of pressure happening when you had the old brakes in. If the pads were badly worn up front the piston in the caliper may have come out too far, and damaged the seal when it was pushed back in for the new pads. A leak from the caliper piston will be hard to see without taking the brakes apart again. If you can't build up a pressure by pumping then a leak from a caliper piston or the rear cylinder (assuming a similar problem) may be the source.

Icedawg, when I changed the pads and rotors, I pulled the pistons / calipers apart and cleaned them up. I didn't replace the gaskets because they looked alright (although at the time I didn't think they might be leaking so I didn't focus on them). If they were leaking now, would I be able to see fluid on the rotor or around the pistons?

[Icedawg]

^
You should see fluid around the pistons. If it leaks long enough and badly enough you would see it without taking apart the brakes. But it might not have reached that point yet, so you may have to take off the drums, or take out the pads to look at the area around the pistons.

[WmWatt]

The original post says no leaks, new master cyclinder, etc. People suggest air still in a line. When the master cylinder was replaced air could get in the line at the top end and not show up as bubbles when bleeding unless the whole line is flushed? Let's say partial bleeding moves the air down the line and when bleeding stops air floats back up to the top again? Just thinking. Note front lines drop to the caliper but one back line goes up and over the fuel tank. Can't remember where the other back line goes exactly. I replaced all the brake line on mine but not the master cyclinder. I even had one of the rusted front bleeder nipples break off so bled at the end of the rubber hose instead, and brakes worked fine. Good luck.