Brake pedal goes to the floor intermittently

[CARLOS DE LA CRUZ]

I know of an issue with the second gen Ford Escapes where there was some type of issue, possible a software glitch that caused the brake pedal to drop to the floor randomly. Apparently there were multiple cases of this happening but the computer wouldn't record this error and there was no ABS light on. No TSB or update, so switching to a new ABS module could cause the same thing to happen. The problem was present on other Fords as well. Food for thought.

Hoping no with KIA, lol! Thanks

Well, I cant tell you much from the pictures as I am not an expert in your particular vehicle. But the little black "seal piece" looks suspect.

An internal leak would not manifest outside of the system, therefore no fluid would be needed to top off.

"leak" in this case, would be also described as "recirculation of fluid where the fliud can go, but is not supposed to go when the pedal is pressed"

Some systems, like the one I had, had a valve that allowed fluid to flow freely when the pedal was released. This valve was allowing fluid past the main pusher, and accumulating.

In a hydraulic system, a little fluid movement in the wrong area is plenty to kill the pedal. Hydrostatic pressure build and is released much faster than air pressure and there is much less room for error.

Thanks, I will keep an eye on this even I changed the MC, if not more issues, I will post it here to let you all know that is solved. Regards

 

[SeaJay]

Never a good thing.

 

[CARLOS DE LA CRUZ]

I had a similar issue on an older vehicle I had years ago.....one of the most annoying until you know what is actually going on in the system. If you MC is new AND good, then I think you have fixed your issue. Have a good one.

Well, my friend, the new MC did the same thing just few minutes ago, went down to the floor. So, I guess I need to check the ABS? Scanner can check this or not, yellow light is not present in my cluster.

 

[IndyIan]

Hi Guys, well finally you were right on this. I changed my master cylinder. But I have a short story here, I don't want to sound like a fool, but this is my experience here. Also with this problem, the Sorento had bad bushing on the right side lower arm, and also the anti-roll bar bushing. It was causing strange moves when driving, if change the lane left to right, the steering wheel moves suddenly more to the same side and vice versa, during that time I notice the problem on my brake pedal, after 5 days of changing the brake fluid performed the same soft pedal problem once again, but only one more time. In the meantime the new master cylinder arrives, I decided to change all those bushing and working perfect that change, no more strange moves when driving, but also no more issues with the soft pedal. Even that because I was afraid to have an issue with a crash, I change the master cylinder when it arrived and perform the bleeding as I know and really I don't feel any change when I push the brake pedal, I mean it is working, but the feeling on pushing is the same as the old master cylinder and until now no issues with soft pedal. Do you think the suspension issues could cause something like this remotely? Just thinking a little bit crazy here! Well, also I took a picture from the booster inside and clean a little bit that. And never added new bake fluid when I got that problem. Thinking this old master cylinder just started with that problem and was the reason it was intermittent? Or remotely could happen the other I mentioned? Thanks

View attachment 233552

Anti roll bars do nothing for steering wheel angles, or steering at all, until you are doing higher g-force cornering.
Also I would pull the fuse on your ABS and try driving around without it, see if your pedal feels normal. Its not necessary, but you should double check to make sure the bias on your brakes still locks the front tires first. As long as the fronts lock first you are just driving around like everyone did before the late 90s

 

[CARLOS DE LA CRUZ]

Anti roll bars do nothing for steering wheel angles, or steering at all, until you are doing higher g-force cornering.
Also I would pull the fuse on your ABS and try driving around without it, see if your pedal feels normal. Its not necessary, but you should double check to make sure the bias on your brakes still locks the front tires first.

The front tires first? Why?
Thanks

 

[IndyIan]

The front tires first? Why?
Thanks

Understeer is safer, that's the main reason the front sway bar is there too, to promote understeer.

 

[CARLOS DE LA CRUZ]

The front tires first? Why?
Thanks

Also I would pull the fuse on your ABS and try driving around without it, see if your pedal feels normal.
If I remove the fuse, how should it feel?
Thanks again

 

[jetman]

5+ yrs ago our 2012 Lincoln MKX brake pedal started going to the floor for every stop.
The fix was a new hydraulic abs control unit.

 

[CARLOS DE LA CRUZ]

5+ yrs ago our 2012 Lincoln MKX brake pedal started going to the floor for every stop.
The fix was a new hydraulic abs control unit.

Thanks

 

[burbguy82]

Well, my friend, the new MC did the same thing just few minutes ago, went down to the floor. So, I guess I need to check the ABS? Scanner can check this or not, yellow light is not present in my cluster.

Wow. Sorry to hear that. These days, unfortunately you cannot say that the new MC is not the culprit, since parts suck these days. Did you happen to BENCH BLEED the master? Is BENCH BLEEDING necessary for your vehicle? Did you bleed the system after you installed the new master? IS reverse bleeding necessary?

Generally, ABS systems ,mechanically work on a method of accumulation of pressure OR recirculation of fluid, OR both. They can, sometimes can cause this issue, but not without some feed back.

It used to be by "law" ABS systems could not interfere with normal braking, if they failed, hopefully it is the same today, and in your vintage of vehicle. If you remove the ABS fuse, it should disable the system. Will it remove your issue? Not sure.

Really, it is a closed hydraulic system. Assuming 99.999% of the air is out of the system, and your brake pads are not completely worn to the nub and you do not have a leak, you should have a tight pedal.

Some vehicle require a scanner to bleed the ABS, yes.

 

[IndyIan]

Also I would pull the fuse on your ABS and try driving around without it, see if your pedal feels normal.
If I remove the fuse, how should it feel?
Thanks again

Hopefully like normal, but the pedal won't go to the floor randomly anymore. The idea is to see if the abs module is messing things up.

 

[CARLOS DE LA CRUZ]

Wow. Sorry to hear that. These days, unfortunately you cannot say that the new MC is not the culprit, since parts suck these days. Did you happen to BENCH BLEED the master? Is BENCH BLEEDING necessary for your vehicle? Did you bleed the system after you installed the new master? IS reverse bleeding necessary?

Generally, ABS systems ,mechanically work on a method of accumulation of pressure OR recirculation of fluid, OR both. They can, sometimes can cause this issue, but not without some feed back.

It used to be by "law" ABS systems could not interfere with normal braking, if they failed, hopefully it is the same today, and in your vintage of vehicle. If you remove the ABS fuse, it should disable the system. Will it remove your issue? Not sure.

Really, it is a closed hydraulic system. Assuming 99.999% of the air is out of the system, and your brake pads are not completely worn to the nub and you do not have a leak, you should have a tight pedal.

Some vehicle require a scanner to bleed the ABS, yes.

Thanks. Yes, I performed such bleeding to the MC outside, then tires, same procedure as we know starting at the far tire last one the closest one. Someone here mentioned to removed the fuse and it is supposed my brake system will work as the closest 90's, but I have not removed yet, this issue was very intermittent, from 5 to 7 days, after changing the MC, yesterday was the first time, so it means around 13 days or so. Also I saw a video some ABS systems need the scanner to bleed them, I am not sure this could help. Also I measured the moisture and before changing the brake fluid the first time this was good. This time after changing the MC I have not measured, but I would like to go first to check if this need a scanner to bleed. If not sure must be the ABS.
The brake pads in rear side are around 1/8" thickness.
But maybe last December or January I changed the front pads, they went to the nub, only one side, and then changed them. Do you think that could be an issue now, I mean that mistake to let them to go to the nub can cause future problems? Regards

 

[CARLOS DE LA CRUZ]

Hopefully like normal, but the pedal won't go to the floor randomly anymore. The idea is to see if the abs module is messing things up.

Ok, so, I remove it and if this is not happening any more I would assume the ABS is bad, right? What about if this happen again? Thanks

 

[GSCJR]

Further testing will be required if disabling the ABS helps the pressure loss from reoccurring.

 

[CARLOS DE LA CRUZ]

Ok, so, I remove it and if this is not happening any more I would assume the ABS is bad, right? What about if this happen again? Thanks

Further testing will be required if disabling the ABS helps the pressure loss from reoccurring.

So, do you mean, remove the fuse, run the SUV normally and see if I don't loose the pressure again? Thanks

 

[burbguy82]

Thanks. Yes, I performed such bleeding to the MC outside, then tires, same procedure as we know starting at the far tire last one the closest one. Someone here mentioned to removed the fuse and it is supposed my brake system will work as the closest 90's, but I have not removed yet, this issue was very intermittent, from 5 to 7 days, after changing the MC, yesterday was the first time, so it means around 13 days or so. Also I saw a video some ABS systems need the scanner to bleed them, I am not sure this could help. Also I measured the moisture and before changing the brake fluid the first time this was good. This time after changing the MC I have not measured, but I would like to go first to check if this need a scanner to bleed. If not sure must be the ABS.
The brake pads in rear side are around 1/8" thickness.
But maybe last December or January I changed the front pads, they went to the nub, only one side, and then changed them. Do you think that could be an issue now, I mean that mistake to let them to go to the nub can cause future problems? Regards

So in short, yes, having worn pads will effect pedal travel and feel, but NOT all the way to the floor.

So the ABS system works by: when the senses wheel lock during braking, the ABS system starts to divert fluid into an accumulator of some kind.........this is the "internal leak" I was talking about. It is by design, and in proper working fashion, it works, but when it doesnt, it doesnt.

Some say that removing the fuse will fully disable the system, and to this I agree, but the plumbing is still connected. So think on that.

I really dont have much else, so good luck on your issue.

 

[IndyIan]

So, do you mean, remove the fuse, run the SUV normally and see if I don't loose the pressure again? Thanks

Yep, that's what I would try. Do some testing first on a little used road to see what your vehicle brakes like without the ABS module powered. Do some simulated panic stops from 40mph, try some hard stops with some turning to see if the back end wants to come around excessively. If the vehicle behaves itself then drive it for a while and see what happens with pedal pressure.

 

[GSCJR]

So, do you mean, remove the fuse, run the SUV normally and see if I don't loose the pressure again? Thanks

Yep, that's what I would try. Do some testing first on a little used road to see what your vehicle brakes like without the ABS module powered. Do some simulated panic stops from 40mph, try some hard stops with some turning to see if the back end wants to come around excessively. If the vehicle behaves itself then drive it for a while and see what happens with pedal pressure.

Yes, do this

 

[CARLOS DE LA CRUZ]

So in short, yes, having worn pads will effect pedal travel and feel, but NOT all the way to the floor.

So the ABS system works by: when the senses wheel lock during braking, the ABS system starts to divert fluid into an accumulator of some kind.........this is the "internal leak" I was talking about. It is by design, and in proper working fashion, it works, but when it doesnt, it doesnt.

Some say that removing the fuse will fully disable the system, and to this I agree, but the plumbing is still connected. So think on that.

I really dont have much else, so good luck on your issue.

Thanks, I will check it, since last time, last friday, no more issues, this is very intermittent. Really I don't understand if this is ABS or not. Someone told me, also I am sure somebody here mentioned too, I should get the yellow light in my cluster for ABS, but I have not.

 

[CARLOS DE LA CRUZ]

Yep, that's what I would try. Do some testing first on a little used road to see what your vehicle brakes like without the ABS module powered. Do some simulated panic stops from 40mph, try some hard stops with some turning to see if the back end wants to come around excessively. If the vehicle behaves itself then drive it for a while and see what happens with pedal pressure.

Ok, thanks