Lexus Brake Problem

kazuDecember 22, 2006

I own a 98 Lexus ls400 and I have experience this brake problem. On occassion my brake pedal will activate the brakes with less brake pedal travel than normal. The normal brake travel is about 2 inches before the pedal begin to slowly activate the brakes. On occassion the brakes will active the brakes with only about 1/2 inch of brake pedal travel. When this problem occurs I notice it will happen for 3-6 brake application and go away. And sometimes its only one brake appication and it goes away. This happens once a month or sometimes not for 2 - 3 months. When I brought the car into the Lexus dealership they could not duplicate the problem even after a few days. I feel this is a safety issue but unable to make repairs because it happen so infrequently.

Anybody else experience this problem? Thanks in advance for your feedback.



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I can only guess about your brake problem. You have not reported any loss of braking effort, just a momentary change of pedal height when the brakes begin to act, so there may not be any serious problem.

Consider this: Your car probably has an ABS (or anti-skid) system. For some ABS systems, these are not active immediately following a cold engine start, but will check out and prime themselves a few seconds after the transmission had been engaged and the vehicle moved a few feet. In my jeep, I detect this by a pulsing sensation in the brake pedal and a rise of pedal height while backing up from a parked location. The pulse motor can be heard faintly inside the cabin. It lasts for only a second or two. This checkout and priming only happens after the vehicle has been parked for a time. The degree of sensation depends on how much pressue is being applied to the brake pedal during this period.

Could this be what you are detecting?

    Bookmark   December 22, 2006 at 5:33PM
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Thanks Jemdandy,

For taking the time to respond to by brake problem. I don't think that is the problem. I do have ABS. the brakes feeling is the first that I have experienced in my 29 years of driving a vehicle. I have owned 2 other ls400 without this unusal brake pedal problem.

Thanks again,


    Bookmark   December 22, 2006 at 5:40PM
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Could it be that the brake pedal is "hanging up " a bit at times(the 1/2" travel) and completely returning to rest most of the time...
But, this is not very likely with suspended pedals..

    Bookmark   December 26, 2006 at 8:39PM
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It is highly likely that your Lexus came equipped with BA, Brake Assist. The system attempts to determine if your brake application is in PANIC mode and will provide additional brake force if so. Not sure how the system works but I have heard that it monitors the time it takes between gas pedal release and brake application. Another rumor has it that it monitors the initial rate of brake pedal application.

In any case I suspect the result would be much as you describe.

I'm very surprised that the dealer did not know to explain this feature.

    Bookmark   December 30, 2006 at 3:54PM
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This could also be the start of your caliper not realeasing completely or the ruber lines starting to close up.Had this happen a few times myself with other cars. It wouldn't pull either to one side or the other. After a while when you get out of the car you could here the caliper creaking as it started to release completely.

    Bookmark   January 14, 2007 at 12:32AM
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I have the same year model lexus and I have exactly the same problem . The brake pedal travel diffrent sometime s. There be times that I have to floor the hell out of it and be skidding through stop sign and then times when brake pedal doesn't travel much and during breaking driver will almost hit me from behind.

    Bookmark   March 19, 2011 at 11:36PM
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