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Old 07-08-2005, 03:52 AM
Benz300's Avatar
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Lexus brake question

I know i know. It's a "mercedes" forum, but I am hoping someone here could help diagnose this issue.
I'm trying to figure out why there is almost a 2 second lag in the brake effect of the 93LS400.
As an example, If i jam the brakes at moderate speeds, it almost takes 2 to 3 seconds of full pedal pressure before something in the system kicks in and applies full force of the brakes and then the car has the full brakes applied with a rapid jerk. The brakes do engage the moment the pedal is pushed but it almost seems as if the callipers arent exerting their full force on the rotors, or as if the rotors were glazed. (which they arent).
The rapid application is OK but it should happen the moment the brakes are jammed. Not after the lag period.
Once however, the brakes are jammed and ABS kicks in, from there on forward for about an hour or so the brake response does not have any lag in it.
Leave the car over night or drive without slamming the brakes and it goes back to the non-responsive, no crisp 3 second lag braking situaiton.
the car has traction. Does this sound like a bad Master Cylinder or should I be looking at a different component ?
any ideas would be appreciated.

Whether you think you can or cannot, Either way you're right!. by Henry Ford.
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Old 07-08-2005, 08:46 AM
kim Langley
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Sounds to me like there is someting "gumming up the works" >> like the pistons in the caliper are not readily actuating when the brake pedal is depressed.

When was the last time you had your brake fluid replaced .. ?? You might want to start with a brake fluid flush
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Old 07-08-2005, 10:23 AM
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What kind of pads are you using?
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Old 07-08-2005, 11:03 AM
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It doesn't sound mechanical to me. It sounds more like either a brake booster vacuum issue or something in the overengineered ABS system. Remember, the design goal for the Lexus is for the car to be quiet and smooth. The design goal of the MB is for the car to be responsive on the Autobahn at 150MPH plus.

Good luck,
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Old 07-08-2005, 02:44 PM
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Did the 93 Lexus get into brake assist providing like Mercedes. Electrical sensing to figure if your in a panic situation. Its computer controlled.

Definitely get it to the dealer, it's under warranty unless you put 20,000 miles on it a year.

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Old 07-08-2005, 11:08 PM
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No, this year does not have brake assist. the conventional booster attached to a two channel master clyinder which in turns goes into the ABS actuator links to the traction actuator at one end and on the other end goes to the 4 wheels. The ABS is 4 wheel.
I did look in to the possibility of a bad check valve but wasnt sure about that scenario either as a faulty check vavle would usually give a low pedal reserve which is not the case here.
Whether you think you can or cannot, Either way you're right!. by Henry Ford.
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Old 07-08-2005, 11:51 PM
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I have come to the conclusion that this is a part of the designed anti-panic
system.....Volvo acts the same way.
There have been other vehicles I've tested too that have a little less response time.

Although I have not technical feedback from Lexus....I do know that Volvo was designing in anti-panic geometry into the steering as long ago as 1980 on the 240's.
[ ]

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Old 07-13-2005, 02:01 AM
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I test drove a couple of other cars same year and model and those cars didnt exhibit the same symptoms. Hence the conclusion that such behavior is not normal.
Any other suggestions ?

Also would someone kindly recommend a good lexus/import shop in NJ. I've tried contacting all the Mercedes independent shops and they pretty much refused to work on Japanese cars. They mentioned they only work on German automobiles.

Whether you think you can or cannot, Either way you're right!. by Henry Ford.

Last edited by Benz300; 07-13-2005 at 02:08 AM.
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