hi- just purchased a 2006 GX 470 (31k miles) Monday. Driving home today noticed that as i would brake the pedal would stair step down to the floor. If i released the brake and resumed braking the stair step would in effect stop. I drove the car into the local Lexus service shop. They didnt have a real explanation. Did ask if there was grinding--which there wasn't--the car was state inspected on Monday(no brake issues). There were no warning lights on (abs etc etc).Lexus was very accomodating and said they would have their techs check it out tomorrow. I will post their findings asap--just curious if anyone has experienced this before ? thanks, Shawn

There was a TSB for the GX back in 2004 for a condition that sounds similar to this. The fix was to install special front pad shims if the customer complained about the brake pedal intermittently feeling like it was going too far to the floor or if they noticed pulsating (not like when the ABS kick's in). I would have thought this would have been fixed over the two year production run period between 04/06 but maybe not... I had the fix done to my 04 at the time and the problem went away.

TSIB number is BR001-06

Here's some of the detail on the TSB...

BR001-06 INCONSISTENT OR UNUSUAL BRAKE FEELING
3/17/2006 - 2003 – 2005 model year Lexus GX470 vehicles produced BEFORE the Production Change Effective VIN within this TSIB.

Some customers may experience a slightly lower brake pedal feel intermittently. A new brake pad anti-squeal shim service part has been developed to address this concern.

File is associated with other vehicles. 2003 Lexus GX470 2004 Lexus GX470 2005 Lexus GX470 03-17-2006

00106 10019657 20060317 030000 SERVICE BRAKES, HYDRAULIC LEXUS GX470 2004 20060413 INCONSISTENT OR UNUSUAL BRAKE FEELING

Smic there are various factors to the Pedal sink on application. I have listed some which most probably could be the root causes & its remedy.
1. Air in hydraulic system. (remedy) Bleed hydraulic system.
2. Low brake fluid level. (remedy) Fill master cylinder and bleed hydraulic system.
3. Residual pressure check valves not holding pressure in lines. (remedy) Pump brake pedal look for bubbles or fluid swirl at compensating port in reservoir. Replace master cylinder.
4. Excessive clearance between drums and linings.(remedy) Set parking brake and pump brake pedal. If pedal height raises and is normal, adjust Brakes