Air can’t make its own way out of the brake system - unless there is a leak - in which case you will be losing brake fluid, and air would probably come back in through the leak anyway.
Does this car have drum or disc brakes in the rear? If drum someone needs to make sure the automatic adjusters are working correctly. If it doesn’t have drums, forget that and go back to all of the other suggestions.
It may be expensive, but it will be a lot cheaper than hitting something.
it has disc brakes front and back… it’s strange but the brake now feels fine now, doesn’t feel spongy any more, how come?
i still have a mushy brake but there seem no visible fluid leak as the fluid level is near full in the reservoir.
it feels like i still have air in the line. the pedal doesnt go all the way to the floor so master cylinder is prob ok?
suppose one caliper is leaking air, when i bleed the lines, would i have most air from that line thus indicating that caliper is bad?
@michaelscai
Please refresh my memory . . .
Please describe exactly how you performed this brake fluid flush
The pedal feels spongy but no signs of leaks and the fluid level remains the same? Sure sounds like there may be some air remaining somewhere. I sometimes have to re-bleed my truck’s brakes a week or so after the first bleeding, but this second bleed procedure is all that is ever required.
hmmm … well, here’s some ideas.
If you’ve never worked on brakes before and don’t know someone who has to show you how, don’t attempt brake work yourself. Brakes are just too critical to your safety and the safety of others. Ask a pro for help instead.
Soft pedal can be caused by problems other than air. If the brake lines expand under pressure, like a balloon, that can feel like a spongy pedal. One or more of the rubber brake lines may be failing.
Posters have said here that they’ve been able to remove especially stubborn air by using gravity bleed rather than pumping the brake pedal. Sometime the pumping of the pedal during the bleed procedure introduces unwanted air in some brake systems. Since the MC is higher up than the calipers, the idea is you simply open the bleeder on a caliper and let the brake fluid drip out by the force of gravity. No pumping of the pedal. I’ve never tried this, but it seems like it should work pretty good as long as you have the patience for it. You have to remember to close the bleeder valve before driving the car, that’s probably the biggest downside to this method.
Gravity bleeding has always given me a better pedal feel. Might be from the helpers I use (kids or wife). I give them instructions and make sure they are following it, but can never be 100% sure.
I have a diaphragm brake bleeder and various adapters, and I prefer using it, versus the 2 man method where 1 guy is manning the pedal and the other is cracking the line open
But I’ve also done gravity bleeding in emergency situations. It works, but you’d better have a good amount of patience. And you have to pay attention, so that the hose is always submerged in brake fluid. The bottle you use should be a clear plastic bottle, and the hose you use should be clear plastic, so that you can carefully observe the flow of brake fluid and bubbles
actually the reservior fluid level is lower than before, so there is probably some slow leak, taking it back to the shop to get it looked at again this week, hope they can find the leak, its no point to keep rebleed it if they cant find the leak…
So the fluid level is lower, which means it’s disappearing somewhere
Just a thought, in case there is no visible leak . . .
The master cylinder may be leaking INTO the brake booster
But check the calipers, hoses and lines first
If the brake booster diaphragm splits and allows brake fluid to pass though, brake fluid can then sometimes get sucked into the intake manifold and cause the engine to run poorly. If you notice OP that the engine isn’t idling as smoothly as before, then it is especially important to consider @db4690 's comment above.
The brake fluid level will decline as the pads wear. All of that pad material is slowly disappearing over time. Thus the caliper pistons are extended more and more over time. The space behind is taken up by brake fluid. Often getting to “low” brake fluid becomes and indicator that one needs new brakes.
I’m not saying that there is no leak. Any or all of the ideas here are possible, including leaks. The fact is that no one is going to be able to tell you what is wrong by internet.