Brake pedal fade

lincoln
mkz

#1

My brake pedal will fade to the floor after a stop and sitting at a stop lite. The car stops fine. The dealership says this normal. All the training I have had in hydraulics says this is not normal. The dealership let me try a 2007 and a 2010 mkz and they both had this fade. Where is the fluid going in the system to cause this fade?



Bill


#2

First, we need to clarify terms.

“Brake fade”, which is rarely seen these days, is the phenomenon that takes place when overheated brakes cease to be effective until they cool down. This was very common with drum brakes, but is rare with disc brakes–unless someone overuses the brakes on a very long, steep downgrade. When brake fade takes place, the pedal either feels “normal”, or it may seem to be very hard to depress. However, it does not sink to the floor.

That being said, what you describe is almost always an indication of a failing brake master cylinder. However, if you observed this phenomenon with a 2007 and a 2010 MKZ, as well as on your mystery (unknown model year) MKZ, then perhaps this is “normal” for that model.

Personally speaking, I would find this situation to be very unnerving. I assume that you either did not do much of a test drive, prior to buying the MKZ, or that the car that you drove did not exhibit this behavior that the dealer tells you is “normal”. As to where the fluid is going when the pedal sinks to the floor…

Please post back with the following information:
Model year
Odometer mileage
Brake maintenance/repair history


#3

I’ve never heard of any vehicle in which the brake pedal goes to the floor under “normal” circumstances. A brake pedal going to the floor usually indicates a bad master cylinder.

I’d be afraid to drive your car down a long, steep grade.


#4

Does the pedal really bottom out? Or, is it that you can continue to push it down some? I have heard that replacement of the brake hoses/lines with good aftermarket ones can greatly firm up the feel of the brake pedal on these cars. (The hoses/lines are expanding under pressure, that’s where the fluid goes.)


#5

This lincoln is an 2008 with just over 18,000 miles and the fade is so gradual that it is hard to notice and if your foot is not squarely on the brake pedal your foot will engage the top of the accellerator during the fade and could cause you problems. The dealership did replace the hydraulic control unit, but the problem still persists.

Bill