brake issue

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smurfslayer

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Not to browbeat you... well, ok, it’s been a while since I participated in a real good interrogation.

you didn’t answer the question about how old the brake fluid is. Has it ever been changed? If not, how long have you had the vehicle? if it has been changed, when? How many miles/months?

What did you know and when did you know it?
Kidding about that part. :biggrin:





do you have one of those laser thermometers? If not, get one. get a measurement on both front rotors at the bottom of the mountain. Repeat.
Report back with results, or in the event of an unfortunate Raptor incident, have your next of kin update us. :biggrin:

what are the numbers?
The one I got from amazon was not expensive, and I’ve seen over 1100F on one of my suppressors.

The fronts are going to do most of the work, they’re taking the bulk of the load on any vehicle. On a bike, it’s 70-75% of your stopping power up front. you have a master cylinder with mere ounces of fluid, so if it’s old, it will boil faster and the lever consistency goes as does your brake effectiveness.

I think Ford is still - or was then for Jennifers, using the dot 3/4 fluid, but Ford’s brake fluid has a respectable boiling point. Yeah, you can get better, but bang for the buck the Ford brake fluid is legit. but if it’s old, is $hit.
I think it’s DOT 5.0 that is silicone based fluid (don’t quote me on this) that some vehicles use, it’s somewhat less susceptible to water absorption and it’s totally incompatible with 3/4 systems.

I’m going to slightly disagree with @J. Wolfe
don’t change more than one thing at a time.

if you do fluid and it fixes the problem, @Aaron’s your uncle and you’re done.
if you do both, and say you miss clearing the wheels and tires with the new line lock to lock at full suspension travel and let’s say you go marauding down the mountain and you start to lose brakes.

The first track day I went to I had the local stealership do lines and fluid for me and behold - one of my front tires was rubbing the new line at full lock and it wore through. On the street.

so yes, stainless lines will help feel, consistency and will last a long time, but I don’t think that’s the problem here.
 
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Not to browbeat you... well, ok, it’s been a while since I participated in a real good interrogation.

you didn’t answer the question about how old the brake fluid is. Has it ever been changed? If not, how long have you had the vehicle? if it has been changed, when? How many miles/months?

What did you know and when did you know it?
Kidding about that part. :biggrin:





do you have one of those laser thermometers? If not, get one. get a measurement on both front rotors at the bottom of the mountain. Repeat.
Report back with results, or in the event of an unfortunate Raptor incident, have your next of kin update us. :biggrin:

what are the numbers?
The one I got from amazon was not expensive, and I’ve seen over 1100F on one of my suppressors.

The fronts are going to do most of the work, they’re taking the bulk of the load on any vehicle. On a bike, it’s 70-75% of your stopping power up front. you have a master cylinder with mere ounces of fluid, so if it’s old, it will boil faster and the lever consistency goes as does your brake effectiveness.

I think Ford is still - or was then for Jennifers, using the dot 3/4 fluid, but Ford’s brake fluid has a respectable boiling point. Yeah, you can get better, but bang for the buck the Ford brake fluid is legit. but if it’s old, is $hit.
I think it’s DOT 5.0 that is silicone based fluid (don’t quote me on this) that some vehicles use, it’s somewhat less susceptible to water absorption and it’s totally incompatible with 3/4 systems.

I’m going to slightly disagree with @J. Wolfe
don’t change more than one thing at a time.

if you do fluid and it fixes the problem, @Aaron’s your uncle and you’re done.
if you do both, and say you miss clearing the wheels and tires with the new line lock to lock at full suspension travel and let’s say you go marauding down the mountain and you start to lose brakes.

The first track day I went to I had the local stealership do lines and fluid for me and behold - one of my front tires was rubbing the new line at full lock and it wore through. On the street.

so yes, stainless lines will help feel, consistency and will last a long time, but I don’t think that’s the problem here.
i had the ford maintenence plan for 100k miles. truck now has 130k. not sure if or what the dealer ever did to the fluid
 

BenBB

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i had the ford maintenence plan for 100k miles. truck now has 130k. not sure if or what the dealer ever did to the fluid

I agree with others, fresh brake fluid would be where I started. Speed Bleeders makes the job easier but by no means a necessity. But that fluid is really old, it's time regardless of if it's causing the issue at hand.

If the problem persists and you're sure there's no external leaks I would think (quite possibly incorrectly) that that would point to master cylinder or brake booster. Seems like I've seen a lot more threads about booster issues than master cylinder, so I'd start diagnosis there. Good luck, let us know what you find.
 
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found something else now that i can replicate almost all the time. if i push the brakes to the floor, le5 off and immediately re apply the brakes, it feels as its almost frozen in place. i cant push them down past a certain point. yet i let off for a couple seconds and hit the brakes again, it moves all the way down
 

J DAMAGE

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found something else now that i can replicate almost all the time. if i push the brakes to the floor, le5 off and immediately re apply the brakes, it feels as its almost frozen in place. i cant push them down past a certain point. yet i let off for a couple seconds and hit the brakes again, it moves all the way down

That sounds like a master cylinder problem. There’s a series of seals in the unit, depending on what is bad, you will have no signs of leaks. Then the other expensive side of it is the ABS MODULE, fingers crossed.
 
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smurfslayer

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That does sound odd. The fluid is suspect at best, change it. That’s not expensive and you should be changing it anyway.

I am trying to think back, but I don’t think I’ve ever killed a master cylinder. I’m not saying that’s wrong - it does sound suspiciously like it could be that, just that I’ve never had one go out on me.

I have had a bmw abs module go out on me, made by effete German engineers entirely too impressed with their own competence.

Come to think of it, that failure went like this - brake, brake, brake harder because not slowing down fast enough, brake feel goes to zero. Downshift rapidly, pump brakes again, zero brake feel and then BOOM - ABS fault and full lock up (because the brakes were fully depressed). In my case the abs fault caused brakes to perform normal braking, which worked like they should immediately after fault!

This was a rental, and one of the reasons I pity bmw owners and am a FRF branded “euro-phobe”. :biggrin:
 

J DAMAGE

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That does sound odd. The fluid is suspect at best, change it. That’s not expensive and you should be changing it anyway.

I am trying to think back, but I don’t think I’ve ever killed a master cylinder. I’m not saying that’s wrong - it does sound suspiciously like it could be that, just that I’ve never had one go out on me.

I have had a bmw abs module go out on me, made by effete German engineers entirely too impressed with their own competence.

Come to think of it, that failure went like this - brake, brake, brake harder because not slowing down fast enough, brake feel goes to zero. Downshift rapidly, pump brakes again, zero brake feel and then BOOM - ABS fault and full lock up (because the brakes were fully depressed). In my case the abs fault caused brakes to perform normal braking, which worked like they should immediately after fault!

This was a rental, and one of the reasons I pity bmw owners and am a FRF branded “euro-phobe”. :biggrin:

Just replaced one on a 2014 f150 in work, if the most inner seals fail, hard to find, if the rear most seal fails, you get fluid between the booster and master cylinder, and sometimes have to loosen it just a little to see the leak.
 
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