1st it's helpful to mention the year make, model, maybe a couple other details like does it have 4 wheel disc, abs, whatever. Not to me, but to a current mechanic it could matter.

In brake systems that I'm familiar with, the peddle going to the floor without a loss of fluid can pretty much only be an internal leak in the master cylinder. You should be able to feel the drag if a caliper is sticking, and that usually makes the peddle feel harder till the brake fluid boils. You should be able to tell something is way wrong before that. There might be other possibilities in these new fangled cars. I don't know.

The lemon law could apply if this is a new car under warranty. I'm sure the problem as described is correctable though.

sorry for the lack of information. 2006 Hyundai Santa Fe. It does have abs... I am not 100% but I think the front brakes are pads. I am at a loss. Like I said before...... everytime we pick up the car from the service center ( I use this term lightly) the brakes will last a short time then go back straight to the floor. The brake fluid level remains at the max level. The car is still under warranty but this drives me beyond the point of insanity ( no pun intended).
Thank you for your response.

Does this vehicle have drum and shoe brakes on the rear? I'm suspecting a set of brake shoes spaced too far from the drum (very much out of adjustment, maybe the adusters are fouled, or other malady).

A couple of questions to add to jemdandy's. When this low peddle condition occurs, is that something that happens all of a sudden, or does it get lower and lower over time? Does the peddle feel spongy or still firm, but just low when this happens? Does pumping the brake peddle change how high the peddle is when this happens?

Our Steelers didn't look too good in the second half of sunday's game. Hopefully they have brought back a few lessons that will be very necessary if they get to meet the Pats again this year in the playoffs. The Pat's look almost unbeatable.

Now brakes. There are so many things that need to be examined here. Driving habits are important to the diagnosis. Heavy intown use, lot's of stop and go with little time for the brakes to cool off can lead to boiling of the fluid. This happens easier as the brake fluid absorbs water right out of the air overtime. Being a 2006 that would not be something I would expect to see, but that could be part of the puzzle.

Question. When the problem happens, is one brake rotoir hotter than the other in the front? Are the front brakes both significantly hotter than the rear?

I would use an infrared thermometer and actually measure brake temperatures during both a normal use situation, and then compare them to what is happening during a failure event.

Could the pads show signs of whats happening? Not really. No more than what your description of the failure does.
We need to seperate whether there is some type of hydraulic problem allowing air into the system, (very rare BTW without a visible leak) or if the brakes are dragging because of a mechanical problem on the car, or if they are dragging because of operator habits. Just like any other "investigator" all of these are possible until they are confidently ruled out.

What other details can you tell us about the failure? This will be practice to assist the dealership in their re-creating the failure for testing.

If you drove a certain distance today, how far would you have to go in order for the failure to most likely present itself?

Does where you drive the car seem to have anything to do with the problem? In town, local highway, interstate?

In driving in one of the previous situations, is the failure "Unlikely" to occur? (This is critical for the technician to get to experience the failure for diagnostics)

Most of all DONT GUESS, whats wrong such as the way your post title starts, "brake calipers". If you go in telling them the calipers are bad, and they find a problem with them, they would replace them. But that could easily have nothing at all to do with the brake pedal problem! Stick to the symptom, what it feels like, when it occurs, and if there is something that you can think of that is likely to either get the symptom to show up, or not show up at all.

Guessing is very bad as John pointed out. I had a problem with a Volkswagon years ago that ran rough and shook when driving slowly. The mechanic replaced one part at a time based on my guesses until I hit on the carb as the cause.

Consult your friends for their trusted mechanic and take the car there. Tell them what it does and when. A good shop can find the cause and get the car fixed without running up a huge bill.

Now, they are telling me one of my calipers was sticking causing this to happen. Could that really be the cause?

> Could be. The seal blows out and the brake stays on. Do the wheels get hot ?

Shouldn't they have been able to ge the correct diagnosis the first time by looking at the brake pad?

> Not necessarily. The amount of fluid leaking through the seal might not be enough to notice.

Thank you all for your input. To answer a few questions through out the conversations:
Does pumping the brake peddle change how high the peddle is when this happens? The first 4 times..no. The last time ..yes. I could pump the brake and get some resistance back. Then it would go back out when I would stop.

When this low peddle condition occurs, is that something that happens all of a sudden, or does it get lower and lower over time? I could feel the brakes going over a couple of days then they were gone. Approx. 200-300 miles after the repair. The pedal will have no resistance.. no spongy or firm feeling.

when the problem happens, is one brake rotoir hotter than the other in the front? I was told the front rotors had hot spots.

Does where you drive the car seem to have anything to do with the problem? In town, local highway, interstate? All local highway driving.

Again.. I would like to thank everybody for taking the time to put together some insightful answers. I have certainly gained some knowledge about this situation. I just want to make sure the dealership is not grasping at straws. I realize the calipers may be bad but...I want to make sure that something else is not wrong and a side affect is the calipers going bad. Did the master cylinder make the calipers go bad or can the calipers make the master cylinder go bad?????

Thanks again!!!!

**When this low peddle condition occurs, is that something that happens all of a sudden, or does it get lower and lower over time? I could feel the brakes going over a couple of days then they were gone. Approx. 200-300 miles after the repair. The pedal will have no resistance.. no spongy or firm feeling.**

That sounds so strange to me. More questions. Does that red brake failure/park brake, or yellow abs light come on when this happens? How many miles are on this car and the brakes that are on it now?

If it has rear drum brakes, the end result sounds could be an adjustment problem. I would suggest if it does have rear drum brakes that they check that they are assembled correctly and don't have it put together backwards somehow and the adjusters work. Based on my out of date understanding of hydraulic brakes, my money is still on the master cylinder.

Whenever you get the problem solved, please post what it turns out being. I'd like to know.

With what you just wrote, I'll advise stop driving the car until you KNOW this is fixed.

One of the most difficult parts of working in the automotive service "industry", communication.

"when the problem happens, is one brake rotoir hotter than the other in the front?"

>> I was told the front rotors had hot spots.

That's not the answer I am looking for. Hot spots in BOTH rotors tell me some operating characteristic is overworking the brakes. With a temperature probe I want to see if both brakes are equally hot, or if one is hotter than the other which would indicate unballanced operation.

"In town, local highway, interstate?"

>>All local highway driving.

How much distance between stops? How frequently do you have to stop? Are there any significant hills requiring you to hold the car back with the brakes?

With brake operation like this next sentence, PARK THE CAR, and GET IT TOWED!!!

"Does pumping the brake peddle change how high the peddle is when this happens?"

>>>The first 4 times..no. The last time ..yes. I could pump the brake and get some resistance back. Then it would go back out when I would stop

There are two possibilites here. While air in the system would do this, it would be there all of the time and not come and go. From there you are either overheating the brakes, and boiling the fluid. The fluid vapor can be compressed creating the spongy pedal, where full liquid gives you the firm pedal. Or one other possibility is a loss of pressure inside the braking system, this could happen from a master cylinder problem, or from an antilock brake issue that is allowing a bleed valve to let braking pressure flow into an accumulator, basically 1/2 of the antilock activation. In anti-lock the system not only bleeds some pressure off to allow the brake to release from being locked up it truns around and pressurizes the system back up, only it does it 20-30 times a second. That's why you hear a buzz during anti-lock.

This car isn't going into anti-lock is it? Has your description started us down the wrong path?

The dealership technician is very likely grasping at straws at this point. I am questioning exactly what the symptoms really are at the moment. Without a solid report of exactly what the problems symptoms are, it's very hard to duplicate the failure for testing.