Brake Bleeding

[Grey5.0]

The car on or off has nothing to do with the fluid portion of the brakes. That's all hydraulics. The car running is only to provide vacuum to the booster for power at the pedal (in simple terms). You don't want the car running becasue 1) it's completely unnecessary and 2) no power to the booster provides better feel at the pedal while going through this process.

You will not get fluid coming out of a bleeder port while "holding" the pedal. The fluid in the whole system is statc. And what I mean by that is if the pedal is not actively moving, no fluid is moving. Even with a bleeder open, if the pedal is stationary, you should not have fluid or air gushing out. Maybe a trikle or so, but not flow. This is the same reason you do not want to release the pedal with a bleeder open. You'll suck air back in.

Sorry if it comes across as me mansplaining this to you, but with your statement about no fluid coming out while "holding" the pedal, I just wanted to make sure you're on the right page.

Please mansplain away, I've never had to bleed breaks before ( obviously lol ) and the more I can learn the better.

I re bled all the brakes 3 more times. Starting with the passenger rear then driver rear then passenger front inside the outside then inside then did the driver inside, outside then inside and the same thing. Got it to the point there were 0 bubbles even the extremely small ones.

The pedal is extremely firm when the car is off, exactly how I want it then when I turn the car on I can press it to the floor.

I checked all around the master cylinder/booster for leaks, nothing is under the car. I park the car in the garage in the same spot so if there were leaks Id see them.

The only thing I can think of, about 6 months ago what I assume is a vac line to the booster was a little lose so i simply pushed it back in and its never been lose again.

Or could the pads be very glazed over? I do a lot of triple nickel,tail of the dragon, winding roading driving where I do push the car to the extremes a bit and do brake very hard at times.

Should I try new pads?

Its getting a bit frustrating, the car still stops and I feel confident that it will stop but I want that firm brake feeling.

Thanks again.

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[K4fxd]

If it's going to the floor you either have a leak or air in the system. What you describe, hard pedal engine off and goes to the floor when engine on, is a symptom of a bad master cylinder. Also could be a symptom of air in the ABS unit. Find a way to cycle the ABS system.

My money is on the master.

 

[Grey5.0]

If it's going to the floor you either have a leak or air in the system. What you describe, hard pedal engine off and goes to the floor when engine on, is a symptom of a bad master cylinder. Also could be a symptom of air in the ABS unit. Find a way to cycle the ABS system.

My money is on the master.

Thanks I'll look into that, to be clear the pedal still has some resistance but it can be pushed to the floor.

 

[K4fxd]

to be clear the pedal still has some resistance but it can be pushed to the floor.

Classic symptom of the master cylinder seal cups leaking, or what is really called by-passing.

 

[NightmareMoon]

Thanks I'll look into that, to be clear the pedal still has some resistance but it can be pushed to the floor.

if it can be pushed to the floor only when pushing very hard, I think that’s kind of normal. When the pads are old and thin, I think you get a little more travel IMHO.

If you try, can you lock up the brakes and go into ABS on a hard stop? If so, again probably you’ve bleed well enough. If not, could be old glazed pads or a vacuum issue.

i had a situation where the pedal would make excessive squishing noise and braking effort was soft with a squishy pedal. Replacing the master improved it, but not as night and day as I had hoped.

if your pads are down to 1/4 of stock, its probably time to change them anyway FWIW. Thin pads will get hot faster, transmit more heat to the fluid, and feel less instant

 

[Grey5.0]

if it can be pushed to the floor only when pushing very hard, I think that’s kind of normal. When the pads are old and thin, I think you get a little more travel IMHO.

If you try, can you lock up the brakes and go into ABS on a hard stop? If so, again probably you’ve bleed well enough. If not, could be old glazed pads or a vacuum issue.

i had a situation where the pedal would make excessive squishing noise and braking effort was soft with a squishy pedal. Replacing the master improved it, but not as night and day as I had hoped.

if your pads are down to 1/4 of stock, its probably time to change them anyway FWIW. Thin pads will get hot faster, transmit more heat to the fluid, and feel less instant

this is 100% what im dealing with, I can lock the car up ( could before this round of bleeding, car is still on jacks)

 

[K4fxd]

if it can be pushed to the floor only when pushing very hard, I think that’s kind of normal.

It should stop about 1/2 way to the floor. The test is if at a stop light and firm pressure does the pedal stay put or does it creep down?

 

[Grey5.0]

It should stop about 1/2 way to the floor. The test is if at a stop light and firm pressure does the pedal stay put or does it creep down?

if i remember correctly it stops about half way down but im gonna throw the wheels on and go for a test drive. Right now when I press the pedal with the car running it hits about half way and then I have to press down harder to get all the way down.

 

[Grey5.0]

car still sitting on jacks, got a set of z26s for next to nothing. The rear brake pads are very uneven, the outers are all much more worn and uneven. The inners are all thicker but uneven as well. Not sure if the previous owner only changed the inners or what but waiting on amazon to drop off the fronts.

 

[K4fxd]

The rear brake pads are very uneven, the outers are all much more worn and uneven.

This is usually a lubrication issue. Make sure the slider pins are completely clean and use some kind of brake caliper lube on them. I prefer the moly lube made by mighty brakes but the sil-glide you can buy at most auto parts stores works also.

Lube any place metal touches metal. Just be careful not to get any on the pads.

The other reason for this to happen is a stuck caliper piston. This requires a rebuild to fix.

 

[K4fxd]

Does this point to a master cylinder issue?

Master or a leak.

 

[K4fxd]

99% it's the mastercylinder. Replace it or get the car professionally checked out before it fails totally.

 

[sk47]

Hello; Just read thru this thread. I do not know what the actual issue is from reading. Some godd guesses have been made. First thing is a proper brake system should not allow the pedal to go to the floor. The pedal should get firm at some point.
The suggestions about the master cylinder are sound. There are little rubber (maybe silicone) cups on a shaft in a master cylinder. If those cups are damaged, they will not build up pressure. (NOTE- Been over 20 years since I rebuilt a master cylinder so newer ones may be different) The second thing is the surface of the inside of the master cylinder where the cups move. That surface can be pitted with rust if the brake fluid is allowed to get moisture in it. Brake fluid naturally attracts moisture so this happens easily. Fluid getting by those cups will allow your problem and you will not be leaking any fluid. All this has been pointed to by others already.

What i hope to add is an experience I had a bit over six months ago. It was during the replacement of calipers on a Chevy pickup so may not apply to a Ford. I though of it while reading your thread. My problem came about when i lost too much fluid and allowed air into the antilock plumbing. On my truck I could not bleed the antilock system itself. Over nearly a week I eventually found a way to bleed out all the air. I was on the verge of taking it to a shop with special tools.

I have no idea if my situation in any way fits with your problems but I did make a link back then and will post such. I suspect you are faced with more than one issue. If my link helps, fine. If not i wish you good luck.

Learned a trick about anti-lock brake systems. | 2015+ S550 Mustang Forum (GT, EcoBoost, GT350, GT500, Bullitt, Mach 1) - Mustang6G.com

 

[TeeLew]

Please mansplain away,

Exactly WTF did you expect to find on a Mustang Forum?

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