thisstupidcar

My brakes are fine when the car is off. But when i crank the car they go to the floor and i can barely stop. Ive bench bled the mc and bled the brakes RR FL BL FR. No leaks in the lines or hoses. About to replace mc and booster to see if thats the problem. Any ideas?

ezone

Are caliper slide pins free?
Are pads seized in the brackets (due to rust)?
Rear brakes correctly adjusted?
Handbrake mechanisms not bound up and stuck in the applied position?
I've seen many low pedal complaints caused by these common issues.




Master before booster...booster failure is rare..
Standard booster check is 2 pedal pumps of assist (reserve) after engine is shut off, then pedal gets hard when the vacuum reserve is depleted. Restart engine and pedal drops a little bit as vacuum builds up in the booster again.

No leaks noticed --- but is brake fluid disappearing?
Pull master out and check rear seal for leakage, and see if it has been leaking fluid into the booster. If booster is holding brake fluid then I'd replace it.

thisstupidcar

Is there anyways I could tell if its the mc? And do i need to bleed the brakes if i bench bleed the mc?

I didnt see anything wrong with the mc when i was doing the bench bleed. Appreciate the help.

ezone

Not sure why you would bench bleed a MC that has been in use. Bench bleeding is usually only needed before installing a brand new unit.

IMO The most common failure in a MC is fluid bypassing internally between the front and back halves (due to worn or damaged seal), the result is a brake pedal that sinks toward the floor instead of holding pressure at a steady height. It may be a slow pedal sink, or it may be fast. The rate can vary with pedal position and pressure.
You won't ever see this from the outside, and if you've never experienced what it feels like yourself it may require a process of elimination to figure it out. (that means making sure all 4 brakes are operating perfectly)

Yes you should bleed all 4 wheels. It's rare that you can open brake lines and not get unwanted air trapped somewhere, and any air in the hydraulic system can cause lousy pedal feel.

thisstupidcar

Thats what i was told to do. So I did it. This is my first time doing anything with brakes besides changing them. Most people are saying its the booster. So i ordered a booster and mc from oreillys. Should i just change the mc first and see what happens? If it doesnt work ill have to pull it off and do everything again just to put the booster on.

Also is this the right bleed order for my car?
RIGHT REAR
FRONT LEFT
BACK LEFT
FRONT RIGHT

ezone

You should be getting good at doing the master cylinder by now.

Traditionally you'd start at the brake furthest away from the master cylinder, and work your way inward to the closest.
RR,LR,RF,LF

The few cars I've ever looked up in Hondas service info say to do it the opposite.
LF,RF,LR,RR

The most important thing it to get all of the trapped air out, and you may need to repeat either bleeding routine more than once.

thisstupidcar

I should be but maybe im doing it wrong. Im going to pick up the parts today and start the repairs. Ill post what happens. I appreciate the help ezone.

thisstupidcar

Replaced booster and mc and it fixed the problem.