Brakes from Hell!

Ok my 03 Taurus V6, my brakes are beginning to scare the you know what out of me! Today I was approaching my driveway and applied the brakes to slow down. "BAM" the pedal went right down to the floor with no pressure! The brakes did not apply at all and the car kept right on trucking! I released it, gave it a pump, and re applied and they worked fine! This would not be such a big deal but this is now the third time this has happened in about six months! All three times seem to be after being on the interstate for a while then getting off. All three times the exact same thing happened. Go to apply the brakes and the pedal would hit the floor, the car would not react at all. Thankfully all three times there was nothing in front of me so. . . So far I have been lucky. I would like to get to the bottom of this before my luck runs out! I did recently change the pads and everything seemed fine. I drained all the old fluid and replaced with new at that time. I don't think this has anything to do with it since the first two times happened before the pad change. I checked the fluid when I got home and it was full with no visible signs of leaks. So my question is what would cause this? Could it be air in the lines? That was the only thing I could think of. I am up for any and all suggestions! And thank you all in advance for any advice!

My initial suggestion is to flush the system and use some high-temp synthetic brake fluid. But you mention you replaced the fluid. Did you just suck out what you could get and fill with new, or did you flush the system? If you didn't flush the system, you might try that. If there is moisture in the lines and one of the brakes is dragging, it could be heating the fluid from highway speeds, boiling any moisture in the fluid and causing an air pocket. As you're probably aware, air will compress and can cause the pedal to go to the floor as you are experiencing.

If you did flush the system previously, then you're probably left with trying a new master cylinder.

-Rod

I did just suck out what I could get. I did wait until I had the pistons compressed back into the calipers so I would get as much of it as I could. I will do a system flush! When I did the pads they were all pretty new looking except for one that was completely worn down to nothing but metal! So I did have one brake that was dragging! I pulled the pins, cleaned them, and re greased them hoping that would solve the problem. Apparently I am probably still having the same problem. Thank you for your speedy response.

Do they fail as you're applying the pedal slow, as in an extended braking situation??? What happens when you apply the pedal quickly??? Try both in an empty parking lot, any difference??? I had a car long time ago where the pedal would sink to the floor in a situation such as extended braking down a hill with a stop sign at the bottom, but operate flawlessly otherwise.. master cylinder seals were bad, would only leak in above type deal, long application of pedal..

If you're having a problem with pad wear, there is a caipler problem, or a problem iwth the pins. If the pins slide smoothly, they're ok.....In which case youve got a caliper problem. I havent seen many problems with taurus or sable's, but that doesn't mean it cant happen. If i were you, i would get new pads ( that you need anyhow) and see how easily the good caliper compresses, compare that to your bad side's compression, and if the bad side takes much more force than the good side, go to your local parts store and get a new caliper and hose. I'm ase and ford certified, and as far as flushing the system, screw it, unless you KNOW you have contaminated fluid. Do you have any kind of pulling or anything like that? When at a stop does the pedal sink all the way to the floor? Ford Hasn't had an issue with taurus brakes like this. Trust me, I can look up VIN information, recall, and any recent warranty work.

If nothing else, email me your VIN number, and I can email you any Brake related TSBs (technical service bullitens) specific to your car

The only time they seem to fail is after a long drive. Which leads me to beleive it is a heat related issue! It does not happen during an extended brake. (Like holding them on going down a hill). All three failures have been on a flat surface after a hefty drive. It is very scary because you try to stop and there is literaly nothing! There is no problem with the pedal sinking to the floor except during these failures. I did get new pads and installed them. The pins do slide pretty freely and I don't remember if one caliper took more force than the other. I will check it out though. There was no pull before the new pads and no pull after the pad change. There is no vibration and when the brakes are working they do a great job! Real smooth, fast stop! I will get you the VIN and would really appreciate any information you can come up with!

Is there any chance you overfilled the brake fluid reservoir? I did that once after I changed the pads. Wife said the brakes weren't much there after driving it a few miles on a very hot day. I checked for excessive heat at all four wheels, I can't remember for sure. I think I decided and figured out that the fluid got hot enough to expand enough that the hotter it got, the more the brakes were applied by the force of the expanding fluid, becoming a self perpetuating thing. Anyway, after removing enough fluid, I proved out my theory. Things were fine thereafter.

I like Rod's explaination of moisture and/or air causing your problem.

You may have a bad, sticking caliper or wheel cylinder or collapsed hose or dented line, though that to me doesn't seem quite consistent with your total lack of brakes.

Does anybody here think this could be somehow related to unusually low vacuum from highway driving and/or the vacuum booster/master cylinder isn't right?

You may consider taking it for a short high speed drive with no braking and then try to coast to a stop with no braking. Then check for how hot your four brakes are. They should be cold. Put your fingers on the rotors and drums or callipers. That should eliminate any dragging that may be occurring and instead point you definitely elsewhere, like the fluid. Are you loosing any fluid?

Does anybody here think this could be somehow related to unusually low vacuum from highway driving and/or the vacuum booster/master cylinder isn't right?
I think if it were a vacuum issue, beside the driveability issues with the engine that would probably be experienced, I don't believe it would lead to a pedal going to the floor. Maybe a firm pedal with apparently little effectiveness (due to the loss of power assist). Pedal to the floor would seem to be a master cylinder problem or fluid problem.

I'm not Ford certified, ASE-certified, and I don't even work in the automotive industry, but I don't think that discounts the basics of fluid dynamics and the physics of brake fluid. Hungrycat7, you've posted on this forum before about the sticking caliper slide and excessive pad wear, so there's a pretty good indication your fluid has been quite hot in the past. Also, due to the expense of the ABS pump as well as the inherent safety issues with the braking system, it is never a bad idea to flush the entire braking system.

Brake fluid is hygroscopic (readily absorbs moisture) which can corrode the valves and passages in the ABS pump. Once that happens, you're in for quite an expense if you opt to keep the ABS functional. Thoroughly flush the system with new fluid. The process of bleeding the brakes won't circulate new fluid into the ABS pump though, so unless you have a scan tool to cycle the ABS pump during the flush process, you'll want to find a quiet gravel or sandy road to get the ABS to kick in a few times and get the fresh fluid into and through the pump.

If after this you still experience your braking problems, then consider replacing the master cylinder. Tripletdaddy's question of if there is a drop in fluid level is a good one. If the level is dropping but you don't find a leak, the fluid could be leaking from the master cylinder into the brake booster and causing the booster to fail. While I don't think this would cause the pedal to go to the floor, this would suggest you should replace both the master cylinder and the brake booster.

-Rod

Well I really appreciate everyone's sugestions! I was hoping to get some work done on the brakes today but it was 90 degrees and sunny so I opted to lay at the pool instead :) I like the idea of the heat test. I don't know why I did not think of that but it would be a good indication as to whether or not that caliper is still sticking. I am going to do a complete flush and maybe replace the pins in that caliper. I was hoping to do it tomorrow but it is supposed to storm all day! (I have no garage) I will keep everyone posted as to what happens and what the problem was! Thank again! One more question. . . How exactly do you go about flushing the system?

I like to get a set of speed bleeders bleeder screws and install one in place of the stock bleeders for each caliper. These allow quick and easy one-person bleeding. No, I don't have a vested interest in speed bleeders, I'm just a satisfied consumer. With the speed bleeders, you start at the wheel farthest from the master cylinder, open the bleeder 1/4 to 1/2 turn, put a hose on the bleeder to direct the fluid to a catch can, then slowly cycle the brake pedal. Periodically check the level in the master cylinder and make sure you don't run it dry. Keep cycling the pedal until the fluid coming out the bleeder is clear. Then close the bleeder and move to the next bleeder, working your way towards the caliper nearest to the master cylinder.

I've also been quite pleased with Valvoline SynPower synthetic brake fluid. It is higher temp than most commercial brake fluids and worked well even at the track in my Stealth twin turbo.

-Rod

Oh, now you're just shorod-ing off that you have a Stealth that you take to the track, that your well paying job allows you to afford. (They let EEs in Fluid Dynamics? :shakehead ) But who brags about braking power at the track? Horsepower, torque, acceleration, 1/4 mile times, ......that's what we want to hear about!!! Ok, ok. Sorry about that. :screwy:

But more on topic, I was wondering if the synthetic brake fluid is more resistent to absorbing moisture? It'd be nice if it did.

I tried researching this business of getting the old fluid completely out in Ford's SM with limited success as they have all sorts of fancy doohickies and gadgets for this to run the hydraulic pump and whatnot that us backyard hacks aren't privy to. I wanted to add to what Rod said to get the old fluid out of the abs pump completely by running it during the bleeding process if you have an abs scanner that can do that. Just to fine tune it a bit, irregardless of whether you use the scanner or activate the abs on the road, the only way I could think through to minimize an inevitable amount of old fluid in dilution with the new is as follows:

-suck out all old fluid out of brake fluid reservoir
-refill reservoir with new fluid
-bleed some from one or all wheels (I don't think it matters) but you only need to bleed the LF brake until you get clean new fluid
-then use an abs scanner or braking to activate the abs to pump out the last of the old fluid. This should pump it into the individual brake lines, thus emptying the pump of the old fluid. When the brakes are released, the old fluid will return to the pump reservoir which can then be completely drained by bleeding the brakes. Only problem is, not sure if all the old fluid will come out on a single braking event. You only want one braking event, because subsequent brakings that activate the pump will pump back in cross contaminated fluid, unless you bleed the LF brake after every single abs event. That sounds like a PITA. I don't think I could be bothered.
-then complete the bleeding process using the following order found in Ford's SM, noting its order is different from what one would expect

l RH Rear.

l LH Front.

l LH Rear.

l RH Front.

Everywhere I read, they wanted you to switch braking circuits diagonally, and it seems they also wanted you to follow the old rule of farthest first.


I like to use clear tubing on the bleeder screw, so I can see what comes out right at the bleeder and then I can see when the air bubbles stop coming sooner than with a black hose running into a container. I've been burned by two "one-man" bleeders, so I came up with variations of the two man method.

The synthetic fluid is supposed to be less prone to absorbing moisture.

You do want to bleed all lines prior to the ABS cycling in order to clear as much of the old fluid as possible. Those long runs to the rear of the car can hold a fair amount of old fluid.

PS: I no longer have my Stealth. I traded it in for an SUV, then missed having a sports car (my Lincoln LS didn't qualify) so I traded the LS in on a G35. ;) The part I left out about the track events in the Stealth was where a friend that used to own Stealths before he made good money and bought his twin turbo Porsche 911 took me out in my Stealth to "show me the line" and boiled my brake fluid. Nothing like going 130 at the end of the straight and finding there are almost no brakes to make the 90 degree turn. Good thing he was driving and not me. He kept calm and stayed on the track. That's when I learned the importance of flushing brakes regularly, like the manufacturer suggests. It's amazing how much good information is in the owner's manual!

-Rod

I tried thinking through all of the possible orders and method of bleeding, and concluded, no method, even the dealer's, can completely remove all of the old fluid without disconnecting the ABS HCU pump or an unjustifiable repetitive bleeding process.

I'd say do as Rod suggests following Ford's criss-cross order and ABS cycling and not sweat the remaining old fluid diluting the new fluid. My previous post in hopes of a method that would completely eliminate the old fluid would still remove most of the old fluid as that is the last step. Doing a partial bleed first, ABS cycling second, and finish bleeding last would remove most of the the old fluid without wasting new fluid that is between the diluted new/old fluid at the pump and the brakes that would be created by a full bleed and ABS cycling. This new fluid would be wasted to drain the dilute fluid completely. The two step bleed would illuminate this loss of new fluid, though I have no idea of the actual volume saved.

Oh, btw, how did the brake fluid get so hot on the track? Was that from using the brakes? Or, do they do that on their own? That doesn't sound like a good way to test you brakes. :D :screwy:

I suspect it was from hard braking from 130 mph with 2 people in the car, 4-piston aluminum calipers in the front and single piston calipers in the rear, all clamping hard to make the nearly 90-degree turn coming up in a hurry.

After the fluid cooled the brakes came back and I was able to drive it home. No issues during normal highway driving, and no further issues once I went to the Valvoline SynPower, even at the track. I later installed braided stainless brake hoses which made a surprisingly big difference.

-Rod

Interesting braking system. I'm not familiar with hydraulic braking systems that include some sort of cooler, but I would think it would be necessary in some situations. I'd think that race cars may need that based on your experience. I'm not surprised the braided brake hoses helped reduce the heat in the brake fluid as it works as a good conductor of heat and easily looses it with the small wires, whereas black rubber hoses are really terrible conductors of heat because of thermal resistance and it's a black body, which like to absorb heat.

There wasn't a cooler, other than the large aluminum calipers. I just didn't take the car on the track any more that afternoon, so by the time I was ready to drive home, the fluid was cool and functional again. Maybe I boiled all the moisture out too. ;)

The main benefit of the braided stainless brake hoses is the stainless steel braid keeps the hoses from expanding under braking. On a typical rubber hose, some of the fluid force causes the diameter of the brake hose to expand slightly. The theory of the braid is to reduce that expansion so there is a more efficient transfer of pressure to the brake calipers.

-Rod

I wasn't implying you did have a brake fluid cooler, but just thinking how that might be needed in some scenarios, maybe high speed racing? I don't know. The heat alone certainly could make those rubber hoses expand, then make them mushy, add some pressure, then more heat, and on and on... not good. SS braid sheath makes a lot of sense for that problem. I was just thinking of the added benefit of the cooling the braids could provide as a byproduct of its design, not necessarily a primary design criteria. Though, I wouldn't be surprised if the designers were aware of that attribute when considering using the wire sheath.

To keep the braid from fraying and collecting junk, they cables had a vinyl (or similar) clear coating over them which would reduce any heat transfer benefit from the braid. But they looked "cool" (no pun intended). ;)

-Rod

Do they fail as you're applying the pedal slow, as in an extended braking situation??? What happens when you apply the pedal quickly??? Try both in an empty parking lot, any difference??? I had a car long time ago where the pedal would sink to the floor in a situation such as extended braking down a hill with a stop sign at the bottom, but operate flawlessly otherwise.. master cylinder seals were bad, would only leak in above type deal, long application of pedal..


:1:
It sounds like you have pretty much replaced most of the areas that would cause this issue. I would suspect air in the lines would cause the pedal to be "soft" but not result in it going directly to the floor unless the air pocket was right at the MC. If there were air in only one line I don't think the pedal would go all the way. Try holding the brake down hard for a couple of minutes and see if the pedal slowly starts to sink. If the seals on the MC are bad it should show by allowing the fluid to drain back into the master cylinder instead of holding pressure. :2cents:

To add to RaeRae1's thoughts, if there is some sort of air and/or seal issue right at the MC, wouldn't air bubbles or a small amount of foaming possibly show up in the reservoir? You haven't said if you are loosing fluid or not, which would be consistent with the pedal going to the floor. If so, then you need to find the leak. I think it's been suggested already to check the brake cylinders if no other leaks are found. Have you checked your brake hoses for softness, sponginess, abnormal condition?

Now on those braided brake lines, what a waste of good heat transfer.....another case of form winning over function...tsk,tsk....oh well. :shakehead: Fraying? Eh. Collect junk? Ok. Cool and sleek vinyl coating sounds good, too....

The car is not losing any fluid! I have checked the lines and all looks normal. I am pretty much convinced it is the binding caliper. Just started a new job so as soon as I get a chance I am just going to throw a new caliper on and hopefully be done with it. I think the fluid is just getting too hot!

99% it's the master cylinder. There are two cups in the master cylinder, one for the front brakes and one for the rear brakes, in a straight line ie one in front of the other, fluid gets past the first cup allowing the brake pedal to sink with no external loss of brake fluid. Why doesn't the brake pedal go to the floor every time the brakes are applied? I haven't figured that out. Not only have I experienced this myself and replacing the master cylinder fixed the problem, I have read of this on other forums like this, and yes replacing the master cylinder fixed the problem.