My brake pedal slowly drops all the way down when I apply pressure.?

Question

My pedal slowly drops to the floor when I apply pressure to stop the car
I have no fluid leak or grinding.
Does anyone know what can possibly be the problem ?

I have not had any recent repair on the brakes
it just started doing this recently.
If I pump the brakes then I get the pressure back
but then the pedal slowly goes to the floor again.
Its a 97 honda civic.

Answer 1

There are any number of reasons that a brake pedal gets spongey or sinks like that, but most typically one looks for a leak or a bad master cylinder.

Now as to seeing no leak, it would not be necessary for there to be a puddle of brake fluid on the floor to have a leak. Typically what one sees is some dampness around the wheel cylinders (on drum brakes) or the calipers (on disk brakes) and that dampness will accumulate brake dust. You can pull each wheel and look for that.

Essentially the system works like this: You have a master cylinder, usually mounted on the fire wall in your engine compartment and the brake fluid reservoir sits on top of it. (You can also look for dampness and accumulated dirt trapped in it there which would be indicative of a bad master cylinder). As the name implies, the master cylinder is a cylinder with a large piston inside and that piston is operated by your brake pedal. You push on the pedal, the piston moves forward, and drives brake fluid through the lines to each wheel.

Now at each wheel there is a smaller cylinder, again, on drum brakes simply called a wheel cylinder and on disk brakes the smaller cylinder is located inside the caliper. However, in either case, the brake fluid drives a small piston forward that forces your brake pads or shoes up against the braking surface on the disks or drums and brings the wheel to a stop.

Because it is an hydraulic system it relies upon being able to drive the brake fluid to operate the pistons at each wheel. This means that (1) there can be no leaks that allow the brake fluid to escape, thereby eliminating the pressure it needs to operate, and (2) that there can be no air in the lines as brake fluid cannot be compressed but air can and if there is air in the lines it will simply compress without offering any fluid thrust to the wheel cylinders or calipers. In either case, the pedal will feel spongey and sink to the floor under pressure.

Answer 2

Your master cylinder is worn. The inside has a piston with rubber rings that push the fluid. When they get old fluid starts to slow leak past the seal thus your pedal goes down, and since it it is internal fluid stays inside. Change it soon as when it goes you have no brakes and that's a bad day.

Answer 3

No Brake Pressure

Answer 4

Depending on the year, make and braking system it could be the master cyclinder, powerbrake booster or ABS module. Basically something is not keeping the pressure in your brake lines. If you've replaced anything on the braking system lately it could be as simple as the brakes were not bled out properly also.

Answer 5

you probably have a small leak

if you don't have a leak, then you DID have a leak and now you have air in your brake lines

if you pump the brake pedal and you get full braking after a pump or two, it may just be air in the system that needs to be bled down

get this worked on quickly, it is dangerous to drive with brakes like that

Answer 6

You have a bad master cylinder. The seals inside that create the 300lbs per square inch are failing and they can be very hard to replace depending on the unit. You can buy an entirely new master cylinder for usually under 50 bucks. Good luck.

Answer 7

WIthout a lengthy answer. if you are not losing fluid, it would be your master cylinder, If you are losing fluid, look for leaks first around each wheel, which would indicate a bad wheel cylinder or caliper. if not, have a assistant pump the brake pedal while you look for leaks along the brake lines.

Answer 8

I know this sounds strange coming from a girl, but when you are divorced, there are certain things you learn about....it sounds like you may have air in your lines. Did you just recently have your breaks worked on or bled??? Make sure you do not have a hole in the lines, which could be causing you to lose pressure. I have a CJ-7, and I had this problem before, or similar. We bled them, and still no pressure, we ended up replacing the break lines. Also....do have have any break fluid at all???

Answer 9

Brake fluid leaks inside the wheel-well, if ya have a hub-cap on your tire, ya might not see its leaking. -or- There might be an air bubble or 2 inside your lines & you'll need to bleed your brakes. Check your brake fluid & if it is low you'll need to bleed your brakes. Either way its a simple cure, brakes are easy.

Answer 10

Have your master cylinder checked- there does not have to be an external leak for the master cylinder to be damadged.