Abs Issue?

[SimonG]

Hi Guys

My car (GS450h) went in for a 90k service last week and to see if they could determine the cause of the engine tap/rattle when cold.

Service was completed but the only feedback I had re the engine tap/rattle was to see if it improved after the oil change, but if not it was likely valve noise so expensive to fix (Valve spring recall already done in 2010) :(

Anyway, since getting the car back I've noticed an occasional buzz/vibration through the brake pedal at low speeds after gentle breaking. I can replicate this with the car in neutral & stationary by pressing the brake pedal 5-6 times, then on the 5th or 6th press there is a buzz from the engine bay which is felt through the pedal.

I've no lights lit on the dash and the car drives and stops as normal, so does anyone have any ideas what could be causing this?

Cheers

Simon G

[steve2006]

If the system is similar to the earlier GS models it sounds like the brake accumulator pump kicking in which is normal to maintain full braking pressure to the system.

Unlike most cars there is no conventional vacuum servo unit.

The pump/accumulator/motor for this is normally mounted on rubber bushes and these can wear allowing metal to metal contact to occur hence the noise and vibration you can feel through the pedal.

The system is normally located on the driver's side engine bay bulkhead, if you can get somone to pump the brake pedal to activate the pump it should be fairly easy to locate and see if the rubbers have worn.

The good thing is there is no warning light on for the ABS/TRAC system so this may be as suggested just a simple mechanical defect vibrating excessively.

[SimonG]

Thanks Steve - that actually makes a lot of sense and would explain why the buzz only happens now and then, or after several presses of the brake pedal.

I'll have a look over the weekend and see if I can find something - At least it sound like a relatively cheap fix :)

Cheers

Simon G