SH430

Several months ago I started to notice more brake pedal travel than is normal. The car still stopped okay, but I found myself wanting to double pump the brakes all the time. My first step was to flush the brake system - no improvement. Then I replaced the master cylinder with a new OEM unit and bleed the brakes - no improvement. On the recomendation of a local repair shop I had them replace the brake booster which resulted in only a slight improvement. The brake pads have 15,000 miles on them and still have a lot life left in them. Any ideas?

GeorgeT

I would look closely at the anti-lock brake module -I'm not sure that a typical brake fluid flush will clear that unit.

sojah

iTrader: (1)

sounds weird... it it possible to have another ls430 owner in your neighborhood take a drive and see if it really is that bad cuz correct me if i am wrong but you are a new ls owner right? other than that maybe the pads and rotors need to be replaced,, as in maybe the rotors are old or something. new pads and rotors is what i would have done after bleeding the brake lines.

Jabberwock

I would have replaced the pads first with a stock OEM set also making sure the shims and anything else there looked correct and installed absolutely correct. Also make sure you have the roters measured to insure they are within full spec on thickness. This way you know you are starting fresh - That would be before I started out replacing other brake system parts.

SH430

I did'nt suspect the pads and rotors because, correct me if I'm wrong, disc brakes self adjust, and the pedal feel should not change very much as the pads wear. I've had this car for about two years, but it is my first Lexus. It is strange that the change in pedal feel happened suddenly and not a gradual change. I'll have to ask the dealer about procedure for bleeding brakes / ABS.

sojah

iTrader: (1)

my bad i must have mistook you for someone who had just purchased their ls and had some initial questions... yeah definitely weird if it was fine for so long and then all of the sudden got bad. I would check sooner than later with a tech about it.

playa3uhh

hm... this is interesting. I don't have a lot of knowledge on brakes but if it were me I would change the rotors to drilled/slotted rotors and it could perhaps bring up some other issues. Have you checked the brake lines? Maybe there is a clog or leak somewhere? This is odd. Good luck! Just my two cents.

jayclapp

It might be cheaper in the long run to have your local Lexus dealer diagnose the problem. You might have a problem with the vacuum assist for instance. Just my opinion.

V8_Fan

Try turning off the engine while holding down the brake pedal (like when you pull into your garage). Hold down the brake pedal and count to 20. If it sinks lower, your vacuum booster is bad. If not, it's okay. And no, bleeding the brakes the conventional way (pumping the pedal and working the bleeder valve) doesn't flush the ABS resevoir. You need the Toyota brake bleeder tool or Lexus/Toyota computer tool for that.

SH430

I have finally resolved my soft brake pedal problem! I turned out to be a sticking piston in one of the front calipers.
I checked all of the calipers, front and back, by removing the brake pads, one caliper at a time, and inserting 1/4" wood shims on each side of the rotor. This kept the pistons from comming all the way out of the caliper when I pumped the pedal. I pumped the pedal once or twice and then check the caliper to see how the pistons were moving repeating the procedure until all of the pistons made contact with the wood shims. I eventually found the offending piston in the front left caliper.
When I reassembled the brakes and road tested the car the brakes felt fine! No more soft pedal. I was tempted to leave well enough alone, but I didn't want the problem to come back. So, I called my local Lexus dealer and ordered the "overhaul kit" for the front calipers. The parts guy wasn't sure he had heard right when I asked for the kit, one kit does both calipers, but I wanted to try rebuilding before spending the big bucks for calipers. The calipers were easy to rebuild. The kit had all of the seals, boots and brake line seals. I also replaced the caliper bolts since Lexus recommends not reusing the old ones.
I'm very glad to have solid brakes again! I hope this information helps anyone else having similar problems.

DDLexus

Thanks for closing out this thread. Glad you were able to self diagnose!

GS3Tek

iTrader: (8)

good info

thanks for the update

waijai

iTrader: (9)

Good stuff for all owners to be mindful of.

Jabberwock

Thanks for updating the tread - excellent info on potential brake problem

GRAND_LS 4

iTrader: (2)

Thanks for updating the thread, very good information right there