Brake pedal on floor occasionally 93 Acrd

93 honda Accord-5 spd-2.2L

I flushed the brakes last weekend.
However the next day after about 50 miles of driving, the pedal went to the floor, but on the next pumping, I got enough braking power.

This has continued for the past 3 days and I am suspecting the Master cylinder.
What confuses me is that after the pedal floors, the next pump gets me a good brake.

I'm not sure if I bled the brakes right the last time, I had my friend pump the pedal, while I shut the valve.

Does a failed / failing MC still provide occasional braking or if it has failed does it not provided any braking at all.

Does having air in the system show some of the same symptoms.

Definitely sounds like air got into your brake lines, because the Master wasn't properly bleed. You really should have it done by a professional to be safe.

Yes, this can also happen if you have a slow leak in your MC. Check the Master for any leaks. See if any paint was removed from the body frame, as brake fluid strips paint. Are you losing brake pressure (pedal going to the floor) when sitting at a stop light? If you had a bad leak your pedal would always go the floor.

Like I said definitely sounds like the Master wasn't bled properly.

The bleeding task can be done without professional assistance. The proper way to bleed the brakes is to pump up the pedal with the wheel valves closed. When you have a full pedal, open one of the valves and let the pedal fall to the floor. Do not let the pedal come up until, the valve is closed. Repeat until the fluid is clear and no bubbles. Make sure you keep the master cylinder full. Repeat on all wheels. But it does sound like you have bad master cylinder. If bleeding doesn't solve the problem, you need to rebuild or replace it.

Symptom of a bad master cylinder. Sometimes it's OK. Sometimes the pedal goes to the floor, and pumping gets you brakes again.

Had the same issue with my 95 Accord, only happened when it was hot outside. Replaced the Master Cylinder and problem went away

A bad cylinder usually takes a few pumps to build pressure back up, if it goes to the floor then on the next pump you have pressure, re-bleed the brakes that will more than likely take care of the problem

Sorry to wake this thread up. I purchased a 92 Coupe about a 18 months ago. No problems until a few months ago, on hot days or in bumper traffic, my pedal begins to sink to the floor. Pumping helps but eventually wants to fall again.

I noticed that there had been a leak around the MC where it bolts to the booster. It does not seems like a fresh one but an old one.

My question is, if brake fluid is extremely old and dirty, does it make it perform worse in hot weather? If I flush my entire system using a power bleeder that I have, can I prolong changing the MC ?

Sorry to wake this thread up. I purchased a 92 Coupe about a 18 months ago. No problems until a few months ago, on hot days or in bumper traffic, my pedal begins to sink to the floor. Pumping helps but eventually wants to fall again.

I noticed that there had been a leak around the MC where it bolts to the booster. It does not seems like a fresh one but an old one.

My question is, if brake fluid is extremely old and dirty, does it make it perform worse in hot weather? If I flush my entire system using a power bleeder that I have, can I prolong changing the MC ?

The exact same thing happened to me on my 92 Accord Sedan. The brakes were fine, unless it was hot outside and I was stuck in traffic. My Master has the smallest of leaks. I couldn't even notice the leak and it took my mechanic 10 minutes to find the tiny leak. He replaced the MC and that fixed the problem. For a few years my brake pedal would go down far to the floor when it was hot out. It got a little worse each Summer. My mechanic always dismissed the problem, because the leak was not noticeable.

As for your dirty fluid question I'll let someone else help you who knows more about it, but flushing the brake fluid can't hurt.

ps: My leak was so tiny I could go between oil changes and the brake fluid was still full.

John, thanks for the reply. I think I am going to bite the bullet and order the MC for $67. I rather do a complete repair instead of just bleeding and spending a wasteful $6 on fluid only to do the job a second time.

There was a question about dirty brake fluid and what effect it has on braking.. Well the answer is none immediately. But brake fluid attracts moisture and moisture rusts iron and iron can flake which then acts as an abrasive on the rubber parts and then they start to leak. So, you bleed the brakes to get the bad brake fluid out of the system so the moisture in the fluid won't attack the medal piston cylinders. (both wheel and master) Hope that answers your question.

Sorry to wake this thread up. I purchased a 92 Coupe about a 18 months ago. No problems until a few months ago, on hot days or in bumper traffic, my pedal begins to sink to the floor. Pumping helps but eventually wants to fall again.

I noticed that there had been a leak around the MC where it bolts to the booster. It does not seems like a fresh one but an old one.

My question is, if brake fluid is extremely old and dirty, does it make it perform worse in hot weather? If I flush my entire system using a power bleeder that I have, can I prolong changing the MC ?

Yes it does!

Ask anybody with a motorcycle with a hydraulic clutch. They use brake fluid, and in hot weather/heavy traffic the clutch lever will begin to go dead and not work right when the fluid gets old and has a high moisture content.

This is because the moisture in the fluid is actually getting hot enough to boil, and the vapor released collects as small pockets of compressable gas which give you the same dead pedal and lack of operation that you get from air in the system.

Since it can't escape the system, and just becomes re-integrated with the fluid once it cools off, the problem just gets worse over time. These pockets of moisture are also aggressively attacking metal parts in your brake system, that's why the fluid probably appears so brown and opaque.

If you master cylinder is original, I'd suggest replacing it, as it's probably damaged from years of poor fluid comdition. You symptom can also be caused by deteriorated seals allowing fluid to bypass the MC pistons under certain conditions. That'll also create a dead pedal that comes back up with a pump or two in some conditions, although generally that problem is noticed more in COLD weather, not warm.

After changing the MC, flush the system and have it refilled with Valvoline Synpower DOT4 brake fluid. This is not the same as the silicone DOT5 fluid, which is a PITA and not compatible with other fluids. The DOT4 will resist breakdown and vaporising better than conventional fluid. It is a good compromise, and performs better than DOT3 fluid.

Also guys. About brake bleeding?

When bleeding DO NOT bottom out the brake pedal on each bleed cycle. Also don't bottom it out when pumping up the brakes to bleed, or when bench bleeding. Forcing the pistons into the bottom of the bore is hard on internal parts and can be all it takes to get an older MC to start bypassing fairly soon after a bleeding....

Bottoming the pedal does not get any more out of the system than going 3/4 of the way does. If you can bottom it out, you aren't pushing anything anyway, dig? Just air, and you are only compressing the air further so it can REALLY blow fluid all over your buddy who's working the bleeder screws :lol: You aren't accomplishing anything.

The idea with bleeding is to have the bleeder closed as the pedal is still travelling downward. So you tell the pedal guy "Down", and crack the screw open slightly and shut again, before he bottoms out. Then have him pump a couple of times (not to the floor), then call "down", and crack it briefly and close again. Air moves very fast. All that you are gonna get you'll get in the first instant of opening the screw. But if he bottoms out, and is letting off even slightly before you close the screw, you're sucking a ton of air back in, and wasting your time.

By opening the screw only briefly and NOT allowing him to hit the floor with the pedal, you minimize bleeding time, get a better job done, and minimize possible damage to the internals of the MC.

Jeff, thanks so much for that very intuitive reply. I am glad I ordered the MC and I already have 2 quart bottles of Valvoline brake fluid. I am using the following power bleeder since I have a bunch of friends who have used it successfully. http://www.motiveproducts.com

mpumas, the entire stack of repair records I have when I bought the car do not indicate the MC being replaced. It now has 137K, so since the engine and the manual tranny are in good shape, I'm glad to spend the money for the MC. Thanks.... I guess I won't be prolonging changing it.