Brake Pedal Travels Far But Then Works Good
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Since the car is new to you there are a couple of possibilities. Brake fluid may be low and if the brake booster was changed the the pushrod may not have been adjusted properly. The fluid should be no more than about 1/4" below the top of the master cylinder reservoir. Adjusting the pushrod will require a gauge template to be done exactly and is something I would have a shop do.
Micheal Nadeau
Active Member
Do the brakes pump up - if you repeatedly step on the brake pedal, does it come up higher? If so, you have air in the lines.
If you lengthen the pushrod too much, the brakes will drag.
If you lengthen the pushrod too much, the brakes will drag.
Fox Mustang?
Does pumping the pedal build it up higher?
First thing to really do is this:
Check fluid level
Bleed all 4 wheels, and inspect brake components and make sure they work
Check for leaks
After that, report back.
Does pumping the pedal build it up higher?
First thing to really do is this:
Check fluid level
Bleed all 4 wheels, and inspect brake components and make sure they work
Check for leaks
After that, report back.
I'm subscribing to this one. I am having a similar issue. The deal with mine is as slight pressure is applied to the brake pedal, it will sink down about 1/2 way and then firm up. Then it stops very well. I hate the issue of the crappy pedal but it is also causing an issue with the brake lights. As I begin to press the pedal, the switch starts to encounter the resistance of the pedal and makes the light switch but then as the pedal starts moving towards the floor, the resistance or force taken to push the pedal down decreases enough for the light switch to make/break flashing the damn lights until it gets half way down. Then the lights stay on normally and there is no further sinking to the floor or anything.
My thoughts were maybe there is still some air in the back brake lines that needed to be bled out but the backs have been bled several times to no avail. Ive adjusted up the drums but to get the pedal where it needs to be the drums have to be wayy over tightened to where they are crazy dragging so that is a no go. I havent yet attempted to bleed just the master again and have read there can be issues with the bench bleeding if the proper technique isnt used and I cant remember what took place when I did it. I replaced it about 3 years ago when the master failed and dont drive it all the much. I just remember placing it in a vice with the clear tubing on the ports dumping back into the resivior and pressing a screwdriver into the piston until the air bubbles dissapeared. Oh well, maybe I didnt get all the air out. I was going to get a pressure bleeder and do the whole system just hadnt got to it yet. Its finally cooled down around here in florida enough to get outside and start doing some work again.......; )
My thoughts were maybe there is still some air in the back brake lines that needed to be bled out but the backs have been bled several times to no avail. Ive adjusted up the drums but to get the pedal where it needs to be the drums have to be wayy over tightened to where they are crazy dragging so that is a no go. I havent yet attempted to bleed just the master again and have read there can be issues with the bench bleeding if the proper technique isnt used and I cant remember what took place when I did it. I replaced it about 3 years ago when the master failed and dont drive it all the much. I just remember placing it in a vice with the clear tubing on the ports dumping back into the resivior and pressing a screwdriver into the piston until the air bubbles dissapeared. Oh well, maybe I didnt get all the air out. I was going to get a pressure bleeder and do the whole system just hadnt got to it yet. Its finally cooled down around here in florida enough to get outside and start doing some work again.......; )
I did forget that to answer those previous questions:
1. Pumping the brake pedal does not build it up higher. It also does the same without the booster's assist. Just takes less pedal pressure.
2. Fluid level is ok.
3. Front and rear brakes have been bled. No improvement.
4. All componants are functioning. All mechanicals in rear drums including shoes recently replaced. When slamming brakes at high speed, car does not dive like it would if it was all fronts, stays level during braking and stops very well.
Now that I have been giving this some thought, this only began when this master cylinder was installed. This was never an issue with the original master that was on there up until 3 years ago. Pedal was very firm as soon as pressure was applied.
1. Pumping the brake pedal does not build it up higher. It also does the same without the booster's assist. Just takes less pedal pressure.
2. Fluid level is ok.
3. Front and rear brakes have been bled. No improvement.
4. All componants are functioning. All mechanicals in rear drums including shoes recently replaced. When slamming brakes at high speed, car does not dive like it would if it was all fronts, stays level during braking and stops very well.
Now that I have been giving this some thought, this only began when this master cylinder was installed. This was never an issue with the original master that was on there up until 3 years ago. Pedal was very firm as soon as pressure was applied.
My next suggestion was master cylinder. It's possible it was not bench bled properly and you have air caught in the very front of it.
You can try bench bleeding it again, or replace it.
You can try bench bleeding it again, or replace it.
BMW Rider
Mustang Master
If the pedal is firm, the problem is likely not air in the system. Air will give you a mushy or rubbery feel on the pedal. Low pedal with a solid feel can be one of two things, you either have too much free stroke in the pedal and linkage prior to the MC that needs to be taken up prior to actual force being applied to the system, or one or all of the wheels has too much slack in the shoes or pads which needs to be used up before force is applied.
If the problem is at the MC, you may be able to adjust the mechanical linkage or pushrod length to remove the slack. If this started after you replaced the MC, it is also possible that you ended up with an incorrect part. You indicate that the pedal does not pump up which seems to indicate this is where the problem is.
Too much slack at the wheels will give a low but firm pedal, but will pump up to make the pedal higher. Subsequent driving and reapplication of the pedal will bring you back to a low pedal as the fluid will have been pushed back out to the MC via the drum brake springs or from problems with the disc brakes. The drum brakes are easy to sort so long as they are still within serviceable wear limits and the adjusters are not seized. All that is needed is to take out some of the slack with the adjuster to hold the shoes closer to the drums. For the discs, the problem can be excessive runout on the rotors. Runout will cause the pads to be pushed further away from the rotors as they rotate thus causing a low pedal. Thickness variation can have a similar effect, but will give you a pulsing pedal feel which will be the more apparent symptom. To correct rotor issues you will need to either have the rotors machined, or replace them. A sticking caliper or caliper slide may also create the symptom, but usually poor brake performance will also be present.
If the problem is at the MC, you may be able to adjust the mechanical linkage or pushrod length to remove the slack. If this started after you replaced the MC, it is also possible that you ended up with an incorrect part. You indicate that the pedal does not pump up which seems to indicate this is where the problem is.
Too much slack at the wheels will give a low but firm pedal, but will pump up to make the pedal higher. Subsequent driving and reapplication of the pedal will bring you back to a low pedal as the fluid will have been pushed back out to the MC via the drum brake springs or from problems with the disc brakes. The drum brakes are easy to sort so long as they are still within serviceable wear limits and the adjusters are not seized. All that is needed is to take out some of the slack with the adjuster to hold the shoes closer to the drums. For the discs, the problem can be excessive runout on the rotors. Runout will cause the pads to be pushed further away from the rotors as they rotate thus causing a low pedal. Thickness variation can have a similar effect, but will give you a pulsing pedal feel which will be the more apparent symptom. To correct rotor issues you will need to either have the rotors machined, or replace them. A sticking caliper or caliper slide may also create the symptom, but usually poor brake performance will also be present.
Alright, I changed out the master cylinder but while I had it out I noticed something kinda fishy with the booster. I was just looking at the shaft coming out of the booster and when I grabbed it, the gasket and washer just fell almost completely out and I could see down inside the booster. The shaft was just flopping around and I could just grab it and pull it completely out if I wanted to. Surely that cant be normal. I have honestly never screwed with a booster before at all but this doesnt seem right. The seal should just be held in place by the master cylinder. Seal, shaft and washer. The booster doesnt leak. No hissing or anything from it.
I located the SVO master kit instructions that gives a writeup on how to adjust the pushrod length on the booster. I checked and mine was actually out a bit too far. I tried just for the helluvit and adjusted it out prolly 10mm or so and it made no difference at all. It seems like there is about 2-3 of free travel in the pedal before I encounter any resistance from the brakes. They have been bled and bled and bled. They seem to be air free. I am prolly going to swap the booster and see what happens. I hate just changing parts but I am back job hunting again and my stang is my only transpo for the time being. Its gotta have brakes.
One thing that I just thought of. I was in an accident a few years ago. A limo pulled out in front of me and I slammed on the brakes and plowed right into the side of him. I had my foot square on the brakes so I'm wondering if in the impact something could have gotten bend, over-extended or something. I dunno. Just a thought.
I located the SVO master kit instructions that gives a writeup on how to adjust the pushrod length on the booster. I checked and mine was actually out a bit too far. I tried just for the helluvit and adjusted it out prolly 10mm or so and it made no difference at all. It seems like there is about 2-3 of free travel in the pedal before I encounter any resistance from the brakes. They have been bled and bled and bled. They seem to be air free. I am prolly going to swap the booster and see what happens. I hate just changing parts but I am back job hunting again and my stang is my only transpo for the time being. Its gotta have brakes.
One thing that I just thought of. I was in an accident a few years ago. A limo pulled out in front of me and I slammed on the brakes and plowed right into the side of him. I had my foot square on the brakes so I'm wondering if in the impact something could have gotten bend, over-extended or something. I dunno. Just a thought.
Well, i'd kinda need to see what you are describing, but no, a booster should not do that.
I went and grabbed a new booster at the store and mine is definately not right.....lol. The seal and pushrod are seated firmly and are actually attached to something. I had always figured when they went bad they would develop a vac leak or you would get a hard pedal and whatnot. Either way, the thing is worn the hell out and in need of replacing so I'll swap it. I should see some kind of improvement.
Thanks for the replies so far folks. Naw man, I am running everything bone stock.
Do any of ya'll notice if you look at your clutch and brake pedals side by side that the brake sits about 2-3" lower than the clutch or are ya'lls pretty much sitting right across from each other?
This deal has had be kinda stumped there MFE and I was hoping to get you or one of the other brake guys in on this as I posted a similar thread in the corral. I have just had about 3" of slop in the pedal before it begins to actuate the brakes. I attempted to adjust up the rears figuring that's what it was and all it did was get the back brakes so tight that the car come to a stop on its own without applying the brakes and the slop was still the same. The front pads still have plenty of meat on them and the rear shoes are new as is all the rear mechanicals.
It seems as though there is something amiss between the booster and the master. The booster works but is falling apart as previously mentioned. I adjusted the booster rod per the SVO master kit instructions in order to obtain the D1, D2 and D3 measurements. I'm turning into a parts changer and I do not like it......lol. It gets expensive.
Do any of ya'll notice if you look at your clutch and brake pedals side by side that the brake sits about 2-3" lower than the clutch or are ya'lls pretty much sitting right across from each other?
This deal has had be kinda stumped there MFE and I was hoping to get you or one of the other brake guys in on this as I posted a similar thread in the corral. I have just had about 3" of slop in the pedal before it begins to actuate the brakes. I attempted to adjust up the rears figuring that's what it was and all it did was get the back brakes so tight that the car come to a stop on its own without applying the brakes and the slop was still the same. The front pads still have plenty of meat on them and the rear shoes are new as is all the rear mechanicals.
It seems as though there is something amiss between the booster and the master. The booster works but is falling apart as previously mentioned. I adjusted the booster rod per the SVO master kit instructions in order to obtain the D1, D2 and D3 measurements. I'm turning into a parts changer and I do not like it......lol. It gets expensive.
The difference in pedal height is normal. Clutch pedal is usually higher.
I would swap the booster out first and go from there. I have a feeling you've located your issue.
I would swap the booster out first and go from there. I have a feeling you've located your issue.
Just got done swapping in a new booster and turns out that was the problem. It looks to be just worn the hell out. It never leaked and vac assist still worked but very loose pedal feel. Now the pedal feels like it did when I got it in 96. The main issue I was having is that there wasnt enough resistance in the pedal to keep the brake light switch made so as the pedal would sink the brake lights would come on, go off and then on and you get the idea. I hate when people are up my ass when I'm out toolin around and with the lights doing that 
I think it looked like I was new or something......haha
Anyhoo, I am still on a quest for the perfect pedal tho I do admit. There is still about 2" of slack before the brakes come fully on so I would like to work that out. The pedal feel has been drastically improved with the booster. I may now do some adjusting to backs and bring them up a bit and see how that affects things. Thanks for the input tho. Very much appriciated.
I think it looked like I was new or something......hahaAnyhoo, I am still on a quest for the perfect pedal tho I do admit. There is still about 2" of slack before the brakes come fully on so I would like to work that out. The pedal feel has been drastically improved with the booster. I may now do some adjusting to backs and bring them up a bit and see how that affects things. Thanks for the input tho. Very much appriciated.
May have to adjust the booster rod out a bit to take up the slack. You just don't want to adjust it out far enough that the brakes begin to drag.
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