Brake Pedal Goes to Floor

[msulaimain]

So, recently I was hearing a air leaking noise when pressing my brake pedal and so I have replaced the brake booster and that is fixed, but the brake pedal is still going to the floor, as it was before.

Can anyone provide feedback on the subject?

Oh... and I did bleed the brakes.

I really want to make my brake pedal tight so braking is instant.

Thanks.

It's a 86 honda accord lxi that I'm working on.

[Phatman]

Check your brake lines for holes. Make sure the bleeder valves are all closed. May need to bleed the system more, making sure to start at the wheel the furthest away from the cylinder. If that doesn't do it, replace the master cylinder.

[1989accordaz]

Here is a functional test that may come handy:

1.-With the engine stopped, depress the brake pedal several times, then depress the pedal hard and hold that pressure for 15 seconds. If the pedals sinks, the master cylinder, brake line, rear caliper or a wheel cylinder is faulty.

2.-Start the engine with the pedal depressed, if the pedal sinks slightly, the vacuum booster is working. If the pedal height does not vary, the booster or check valve is faulty.

Leak test

1.- Depress the pedal with the engine running, then stop the engine. If the pedal height does not vary while depressed for 20 seconds, the vacuum booster is ok. If the pedal rises, the booster is faulty.

2.- With the engine stopped, depress the brake pedal several times using normal pressure. When the pedal is first depressed, it should be low. On consecutive applications, the pedal height should gradually rise. If the pedal position does not vary, check the booster check valve.

[1989accordaz]

Phatman, the service manual calls for this bleeding sequence: Front left, right rear, front right, left rear

[msulaimain]

I bled the system in the sequence of rear right, rear left, front right and front left. I replaced the booster and I think it's fine. No leaks.

[RAZR]

Your master cylinder is bad

[derolph]

The brake pedal going to the floor when pushing on the pedal is the problem I experienced with my 4th gen Accord. The solution was a new master cylinder.

[Phatman]

Phatman, the service manual calls for this bleeding sequence: Front left, right rear, front right, left rear

Fair enough. I was taught otherwise, but I guess every car is different. *shrug*

[lostforawhile]

the brakes are split diagonally like many other cars, thats why you dont bleed both sides at the same time, the booster wont make the pedal sink to the floor, thats the master cylinder, also when you take off the master cylinder it has to be bench bled before it goes back on, this is very important, there is lots of info online about how to bench bleed, what method are you using to bleed the wheel cylinders? the oldest way is the best, get a glass jar and fill partly with brake fluid, attach a tight fitting piece of tubing over the bleeder screw, and submerge in the fluid, when you crack the bleeder and push the pedal, the air bubbles will rise to the top, and only fluid will be drawn back in, close the bleeder after no more air bubbles come out, and then remove the hose. It's best to have help doing this. and make sure you dont let the master cylinder run dry, or you will have to bench bleed it again

[gyates93]

You can also buy a brake bleed tool that hooks up to shop compressed air supply, turns bleeding brakes into a one man job, and makes it very easy to completely change your brake fluid without introducing air into the system.

[Phatman]

Not to mention a few other single man bleeding kits. And I'm not talking about cutting yourself. xD

[lostforawhile]

it's not that hard to get someone to press the brake pedal, you can do them the way I suggested by yourself, it's just easier to watch for bubbles if you have help, a jar of brake fluid with a tube in it acts just like the check valve in the one man kit, air bubbles always rise

[Dr_Snooz]

If we're talking about bench bleeding, you can buy a $5 kit from the parts store that makes it a lot easier. As far as overall bleeding goes, I can do it alone, but greatly prefer an assistant.

[msulaimain]

When installing my brake booster, I decided to install my old master cylinder as well, without bench bleeding it, but I did bleed each brake until no bubbles were coming out with one of those tools from Advance Auto (has the nozzle and plastic bottle). Should I put in a new master cylinder and bench bleed it this time? The master cylinder that is on the car is the one that originally was on it at the time of manufacture I believe.

Thanks.

Is there anything else that could be causing the pedal to go to the ground? I don't want to have to put another master cylinder in; getting those lines into the master cylinder is a pain.

[Oldblueaccord]

[IMG] Uploaded with ImageShack.us[/IMG]

I make my own with brake lines.


Another thing with bleeding the brakes you can break the MC by pushing the pedal to the floor. Your just ramming the piston right thru the body of the MC with the pedal leverage. You just want it to drop naturally when the bleeder is cracked open. The pedal will still be several inches off the floor.

[Dr_Snooz]

Should I put in a new master cylinder and bench bleed it this time?

If the pedal feels good, then don't worry about it.

[msulaimain]

So, the pedal is still goes to floor and is fairly loose. I installed an old brake booster from a junk yard, a new master cylinder and bled all brakes. I also adjusted the rear drum brakes. I don't know what else to do. I'm thinking about taking it to a mechanic and seeing what he says about it. I've been looking into adjusting the push rod for the booster from under the dash near the brake pedal. Would that help?

Thanks.

[Oldblueaccord]

So, the pedal is still goes to floor and is fairly loose. I installed an old brake booster from a junk yard, a new master cylinder and bled all brakes. I also adjusted the rear drum brakes. I don't know what else to do. I'm thinking about taking it to a mechanic and seeing what he says about it. I've been looking into adjusting the push rod for the booster from under the dash near the brake pedal. Would that help?

Thanks.

Peek underthedash and see whats up with the pedal linkage itself.

[msulaimain]

It's hooked up right. It's got that pin and it's connected to the booster correctly. I adjusted the rear brakes so that there right up against the drum. What else should I do? I'm stuck.

[lostforawhile]

you need to research how to set the brake pedal free play, if it's too tight you will damage the master cylinder

[Dr_Snooz]

How is the pedal going to the floor? Does it slowly descend when you're stopped at a light or does it flop to the floor with no resistance? If it's slowly descending at lights, then you have a bad master cylinder. There's really nothing else that would cause that symptom beside a fluid leak, which you should be able to see all over your driveway. If it's flopping to the floor with no resistance, then you have a mechanical problem somewhere or a giant fluid leak, which again, you should be able to see all over the driveway.

[lostforawhile]

if it helps, the pedal still has a mechanical linkage to the master cylinder through the booster, the pedal is attached to the pushrod in the booster, the booster pushrod pushes on the rear piston in the master,which pushes the front piston in the master, even if the booster failed, it would be harder to stop, but there is still a direct linkage to the master, look under the dash, see if the pedal linkage is loose or the pin holding the linkage to the booster is loose. also make sure the cotter key is there

[lostforawhile]

if you adjust the free play too tight, the compensating ports on the rear piston will be partially blocked, this will gradually cause the brakes to start locking, until the vacuum is released from the booster

[msulaimain]

Problem solved... I decided to replace both of the rear wheel cylinders since the front tires would slide when pressing the brakes really hard but the rear wheels did not, which told me that something was wrong there. I also replaced the rear brake shoes and the pedal is firm now. Is it usual for the car to take time to completely stop since there's new brakes in the back?

Thanks.

[lostforawhile]

Problem solved... I decided to replace both of the rear wheel cylinders since the front tires would slide when pressing the brakes really hard but the rear wheels did not, which told me that something was wrong there. I also replaced the rear brake shoes and the pedal is firm now. Is it usual for the car to take time to completely stop since there's new brakes in the back?

Thanks.

did you adjust the rear shoes properly?