Indeed several bleed procedures are often required to reach the satisfactory result. I agree that brake bleeding needs to be the first thing to consider.

If the piston is stuck, it causes the car pulling to the side during brake. This is not the case here. The hole in the braking system will cause all the fluid to escape. So this doesnt apply here at all.

One of the key characteristics of the brake fluid is to absorb moisture=water, which finds its way to get to the system. Once moisture exceeds certain amount, it directly affects braking and the very first thing that happens is SPONGY brake pedal.

As Striker said, if the level of brake fluid didn't drop, and i hope if the brake fluid was OEM or of a good quality, this shouldn't cause Master Cylinder to be damaged at this mileage.

 

Here is the Lexus approved troubleshooting guidelines for the brake system (suspected areas in order of diagnostics):

 

I've had 150k miles. My brake pedal was sinking too.
It wasn't the brake level/air.

I did everything at once - replaced the cylinder, rebuilt my brake calipers with new seals, new hoses.

The sinking is gone. So it was either the cylinder or brake calipers.

I've also installed bigger rotors from Lexus GS.

Basically - my brakes are like new without any beating at high speeds.

 

It probably feels great to restore brakes to OEM feel . I remember that days when I also put so much effort into replacing bunch of brake parts, but I mostly worked with what is on the wheel hubs. Didn’t have a chance to replace master cylinder, booster, or even brake lines. But I recall having trouble to properly bleed the brakes, so I had to use Techstream and redo the job several times, as I kept feeling the pedal was dropping way too much.

 

As the OP I mentioned that I did do a thorough brake flush last year with fluid purchased at Lexus. The car does stop really well with no pulling to either side and no pulsating other than the rear rotors just starting to get out of round. After driving awhile I can feel the brake pedal at times has a very slight vibration but no pulsating yet. I’m sure that after 20,000+ miles, with all city driving, I’m going to need within the next year or so a fresh set of pads and will also turn the rotors. I’m not feeling any sinking of the pedal today and wondering if it is even possible for my symptoms being intermittent. I would think not. I’ll certainly be keeping on eye out and will report back this week I just finished a 75 mile trip today with no drama or symptoms. Thanks everyone for such great help! To be continued.

 

Not sure, did anyone suggest brake lines, i.e. checking/replacing them? These are cars no younger than 13 yrs. 5 mos. old but most are 14+ y.o. Spongy feel is why many back in the day replaced brand new hoses with stainless steel/braided.

The way I look at it is brake hoses are like arteries. They harden over time and eventually deteriorate from the inside out. That's where you get fluid forced into a caliper and unable to return/sticking/dragging brakes, or, they give more than they are designed to. A fluid cannot be compressed, so devoid of air, hoses can be a culprit. my .02

edit Also the Lexus methodology imho is for new cars, not 13+ y.o. cars. The other disadvantage is the "drain/fill" mentality, or 80/20 rule. You get a brake flush at Lexus, they only did one caliper, and cars have 4. Your reservoir looks nice and clean, but 3/4 lines are still dirty, and could have air.

 

Although this sounds quite reasonable, we are now touching on the subject of a partial "restoration" for some areas of our almost 20 year old cars. Yes, everything on our cars is getting tired and worn by time and use. Yes, we can start replacing entire systems instead of the suspected parts. Who will actually be doing this other than enthusiasts and those that can repair themselves? Our cars have less and less value and to go further in the repair process other than just fix the probable part is not going to be popular for most owners. I'd love to go the route of the above member of replacing brake lines, caliper seals, master etc. How many owners will actually do this? As our cars get older, I'm sure less will be done for the 4th, 5th and 6th owners to keep our cars going other than the absolute necessities. Unfortunate, but true. We own a large Japanese 4 dr sedan.. No classic car here. PS....When my time comes to relinquish ownership of my LS430, someone is going to get an extremely well maintained car due to an "over the top OCD owner". This is not likely to be the general scenario for the majority of future LS430 purchases. .

 

Why anyone is willing to "cheap out" and use Chinese parts on their brake system is beyond me... but to each his own

 

Agreed. OEM for me.

 

I'm probably missing something. Isn't a brake hose maybe $11 lol and they cause sponginess when they're not up to snuff. "above member" sheesh that's where I do the Jim Croce tune hahahahahahahahahaha

All kidding aside if your brakes feel spongy, how is your car over the top well maintained? That's a major issue as far as perception.

Yes I know we are in a disposable society. It's why most here picked up a LS430 for $5-$15k. Many of the original owners took their cars to Lexus and were told unexpectedly they'd need thousands to fix their cars (mine was $6,500 and for the millionth time nothing was actually needed, it's a Lexus dealer tactic to take the vehicle in trade), when they've always brought them to the dealer all those years.

 

For a DIY everything mentioned above is certainly doable and affordable (although some OEM parts are $$$$) but if dependent upon outside sources it is another story.

 

This is how I would envision it....go to indie shop, and say my brakes feel spongy.

First, they want to road test it, to confirm they also feel the sponginess. If they don't, it's a wrap. If they do....

Most likely they won't take your word for it that it was bled properly, they'll say, hey, we'll lift it and we'll bleed out all 4 calipers. In the worst case scenario, you didn't need it, but we can't take your word for it that there's no air, we've got to go by what we see. At best, you paid $80, and you've got fresh DOT 3 and good for another 24 mos.

Road test again--still spongy. You're out $80, but the baseline had to be established. Now it's something else. Well, your car is at least 13 yr. 5 mo. old, and that's old. Rubber goes bad. sponginess is in fact often caused by brake hoses that are new. We're suggesting to replace the hoses at $35 ea (markup) times 4, but we just bled your brakes as step 1, and you paid us $80, we're willing to just charge you for the parts and see the results. One has to start somewhere, and unlike the dealer, go after the cheap jobs/parts, not the most expensive.

I mean I just read a really long case of a clunk on a 540 BMW with Bilstein PSS9's and B14s, to include Bilstein, the mfg. Troubleshooting may not be what dealers do, but indies do it all day long and methodically. I also learned under the lifetime warranty Bilstein does want the parts back for inspection, and they bench test them. jmo

 

I've had a soft brake pedal feel on my LS430 since day one of ownership, and I've been fine with it as i'm aware that it is a different braking system than a BMW, Audi, Mercedes or Infiniti that characteristically have some initial and immediate "bite" upon braking. When stopping abruptly, my LS430 has always done a good job. Most LS430s I've driven feel similar to mine with regards to the softer braking feel with somewhat more travel. Any sinking of the brake pedal is another story. I could see that replacing brake lines could certainly be helpful especially if the master was going to be replaced at the same time. It is cost effective to do both as long as we are bleeding the system anyway. For the present time, the brake pedal seems to be fine. No further sinking at the moment, but I'll be watching it carefully.

 

What condition are wheel bearings?

If bearing(s) worn, and rotors warble then this could affect travel.and "feel" of brake pedal.

Have your technician check with a dial indicator.

 

Both axle hubs on Passenger side ( front and rear) have been replaced with Koyo axle hubs. All quiet there