dworak

I own Lexus RX330, 2005. When I am breaking at a stop line at the very end it looks like there is gear downshift (rotations jump a little bit etc.). At this moment the car tends to move ahead slightly, so breaking is not smooth. The problem is much more noticeable in hot conditions (sunny day, standing in a traffic jam etc.). It doesn't look the car has problems besides described above - everything works pretty well. The only thing - when the car is parked and I am pressing the brake pedal I hear some strange week vibration noise lasting for 2-3 sec somewhere inside instrumental panel at the left driver's side. Not sure this relates to the problem though.

I visited 2 services (Lexus and Toyota) and they have not found anything unusual. No error codes, parameters (including idle speed) are normal etc. As a preventive treatment they cleaned the throttle, MAF sensor, checked the brakes, flushed braking and transmission fluids and updated transmission firmware to the latest revision. But I am still having the problem.

Some time ago there was a post on exactly the same problem: https://www.clublexus.com/forums/rx-...g-problem.html

Can anybody advise me something? At least I would like to understand is it normal that there is a gear downshift at the very end of braking (almost at the stop line).

Thanks in advance!

salimshah

Do you feel the surge when the A/C cuts in and out? If so it can be your foot is a bit soft on the pedal.

In theory, when the gear shifts down, the engine produces more torque, so if the brakes are being applied gingerly, the vehicle would slightly surge when the rpm bumps up.

I would say ignore the issue, specially when it has been looked at by the dealership.... yes there are times when they pull a snow job, but this one you can reason it out.

Salim

dworak

Problem solved. If you experience problems with brakes or car behavior at low speeds AND hear those strange sounds from driver's side instrument panel area change the check valve on a brake booster. Use a modified metal valve.

Read L-SB-0074-09 TSB for the replacement details. It looks like the laud sound is the beginning of the problems with the valve.

veleno

iTrader: (3)

That would make sense with the brake booster. Glad you could get it diagnosed and fixed.