Usually when there's a sticky piston, it will show on the pads as irregular wear. I guess you were trying to diagnose the problem before the pads showed wear. Another way is to let go of the steering wheel when you hit the brakes, say from 40mph to a dead stop on a flat, smooth road with no cars/people around. The car should track straight. Sticky pistons, even slightly sticky ones, will cause the vehicle to veer to one side or another, depending on how bad the piston(s) is/are sticking.

 

SH430: Can you provide a guide to rebuild the caliper? How easy is easy? Do you have the part number of the rebuild kit for the front calipers?

 

Hi all, revamping old thread here.
First off - THANK YOU SH430 ! Thank you thank you thank you !
You saved me alot of money.
My LS430 was exhibiting same symptoms - big pedal travel (double pumping solving it), no leaks, NO PULL, no irregular pads wear (!).
2 bleeds - no effect.
Next thing was going to be master cylinder...
But then i found this thread, bought 04479-50130 (it does both front calipers!), and did it just now.
Well, i have my tight brakes back !!!!
Thank you again.

PS. i SOLD my previous GM car DUE TO same problem after replacing everything (master, abs assy, all hoses, rear calipers), BUT front calipers...

 

just came across this thread and am having the same problems. Now im ordering up a rebuild kit from Parts.com for 38 bucks. I have already inspected the rotors and changed the pads and even cleaned and tested the pistons in the calipers however I didnt think to use the wooden block method. Very good idea.

 

Is this a common issue with LS430 ?

My 2001 LS430 UL has enough pedal travel before initial bite that it is tough to get used to. I am used to quick progressive brake actuation from other cars I have driven.

Once the pads do hit the rotors the power is strong, but it is more of an OFF/ON type of braking versus a gradual progressive feel.

My brakes have just been bled with fresh fluid and pad have a lot of life left.
My car does not pull to either side when I apply the brakes.

 

Well, to point out, yes, ls430 have somewhat different pedal feel by design. it's a bit more soft and 'travelly' than on some modern cars. But i think it's just a comfort thing - big guy in the back, who bought LS originally for 80+k usd wouldn't be amused if he experienced aggressive braking...
But, that said, there should be no 'sinking', 'mushy pedal' etc.

And yes, many big cars with multiple brake cylinders per wheel, do suffer from this kind of problem and it's usually just a matter of rubber seals and/or brake hoses wear. Microns of extra play in the cylinder/s (or 'bubbling' of old hoses) translates to millimetres and even inches of extra pedal travel.

 

Thanks for that input...

If it make any difference...if I pump the brakes a couple of times, the brake pedal travel decreases noticeably on the last push.

But, after that it is back to the same long pedal travel on the next stop down the road.

 

The LS430 has electronic brake assist so if you jam on it, you'll feel it. Don't worry, it's there.

 

UPDATE to my soft brake issue on my 2001 UL:

I called 3 Lexus specialist shops to see about rebuilding my calipers (they all said NO to that and said that the brakes probably needed another bleed) ...Again stating that the LS430 soft brake feel is normal..

I called my regular mechanic to see if he would do it and he said yes, so i brought over the Lexus caliper seals for the front and back brakes as well as brand new Lexus OEM hoses (per Lynzoid's suggestion). New OEM front brake pads for good measure

Now after the service was completed, it took about 1k miles before I really felt like the brake feel was consistently firm. There were some moments during the 500 mile mark that it felt like the pedal was traveling too far before engaging, but it kept getting better after that.

I mean SOLID firm pedal with a much higher pedal engagement point.

They feel so much better and I don't even think about the brakes anymore, which I can't say was the case before the service. Very reassuring. Brakes that perform like I am driving a car that cost $70k new. Bottom line.

Any tech that tells you that long brake pedal travel and soft pedal feel s normal is telling you BS. They just don't know what the answer is.

 

You're welcome, bro!

 

I was experiencing the same effect and had my local mechanic flush out the whole system. It is much better now. I'm sure it was probably never done (03). Greatly improved the pedal feel and he only charged me 40 bucks.

 

Now this has gotten me to pay more than normal attention to my brakes. :-\

 

I have my brake fluid changed every 30,000 miles as a routine maintenance.

 

So, my brakes got soft again. Damn! I took the car to a local shop where the owner has 20 years Lexus dealership experience. He inspected the brakes and bled the system. No surprise, right? The one interesting thing he told me was that the caliper pistons were retracting too far and leaving a gap between the piston and the brake pad. He did not have an explanation for this condition. I don't know what causes this either, but what I did was measure the gap between every piston and the pads. One wheel at a time, I removed the brake pads where I found a gap larger than .005 (random measurement I chose), I carefully pumped the pedal to move the pistons out to where the pads would not go back in. I then gently worked the pistons back to where I could just get the pads in with a tight fit. I did this until I had a snug fit with a .005 feeler gauge between the piston and the pad. The brakes feel good now, but what will happen as the brake pads wear?

 

I've had pretty soft brakes since I got the car, it feels like I press the brake and theres travel before I even feel anything braking! I've replaced my pads and even master cylinder to to try "fix" this. I failed inspection last week because my car spotted 5 feet more than the inspection allows! I figured maybe I had air in the lines so I just bled them and theres 0 improvement. Any other ideas?