Issue with brakes

A test for a worn Brake Master Cylinder is to hold the brake pedal as if at a traffic light, if the pedal slowly starts to sink to the floor, the master cylinder is failing.

You describe that you can pumpo the pedal and it comes back up, this is another symptom of a failed/failing brake master cylinder.

Since your pedal comes back up, I think your issue is the master cylinder is on its way out. Put your car out of the way of traffic, and (with the engine running) hold the pedal as if you are at a traffic light waiting for it to turn green. If the pedal sinks, you confirm that the master is going out. If the pedal does not sink, then there is something else going on, but pumping the pedal to bring it up points to the master. When the master fails, the brake fluid seeps around the o-rings on the piston and moves between the chambers instead of into the brake pipes that move the fluid to the wheel cylinders -- whether disc or drum, does not matter (the wheel cylinders for drum and disc are significantly different and not interchangable,but the movement of fluid is the same.

Last night I was in a parking spot started up the car and before, obviously, putting it in gear, the brake pedal did go to the floor and was weak to the curb turning onto the street and than maybe 500ft to the corner stop sign was weak as well stopping. I than proceed right make quick left, weak again while braking to turn.

This is the usual pattern even pulling into my driveway thats on a down slope, when I glide into the spot to park applying the brake it goes near to the floor.

Thanks for the help..........;0)

Oh, may seem like a dumb question but will something like this fail

I'm surprised that you got this far with a failing master cylinder.

I have always felt mine slowly sinking long before the pedal goes to the floor without doing anything, or without doing vary much. My brakes have always worked fine, but the pedal would sink as I sat at the light with my foot on the pedal.

Me thinks you should stop driving this car until you can get it fixed. You are well beyond any kind of, "I get this sinking feeling," and are well into, "I mash the pedcal and it goes to the floor and the car does not stop." You get the car to stop, but if yo are having to hit the pedal more than once then your stopping distance is very long, which means your following distance must be longer.

To answer your question, yes it might fail completely. And it might fail the next time you want to stop. As annoying as this might be for you, the guy in front will be completely unprepared as you have a chance to brace yourself. You can do serious damage to somebody, although I already know that you know that.

The car stops though everytime, I mean the pedal is down more than usual but I do see your points & they are WELL noted........;0)

But as I said it only seems to happen at the scenarios given, high speed on the highway the pedal is tight & ready to brake with no sinking.

Thanks for your help Jeff, my mechanic will be looking at it on Tuesday. I really do need to change this mechanic because I described this to him several months ago when it was *slightly* doing it and he said OH all you need is a brake adjustment. He forgets that I KNOW THIS CAR, I am genetically *connected* to it..........LMAO.......I've had it almost

In the meantime practice using the handbrake and note how ineffective it is... be sure to look for a target when braking, something cheap that your insurance will cover completely. Rear ending a Telsa ... that could be expensive.

Actually I could use a new car, any other suggestions?.........;0)

Yaris pretty good

If the master cylinder is on the firewall inside the engine bay, it's pretty easy to replace at home. On my BMW 3 Series, it's under the dash and is a complete pain to contort myself to get to it, but I replaced one on my Jeep that was butt-simple and it took about 15 minutes to hang the new master cylinder. (I needed a helper to bleed the system afterward, but replacing the master cylinder was very easy.)

Replacing the booster is easier than replacing the master cylinder, and depending on the design the master has to be removed to gain access to the booster anyway.

If the master is located in the engine bay, I say buy some parts and do the work yourself. If you have friends or relatives that are better with a wrench than you are, buy them a 30-pack and get them to help you do it right.

REMEMBER Brake Fluid is corrosive, DO NOT GET IT ON ANY PAINTED SURFACE.