valex

my 99LS starts braking when the pedal is 3/4 down, any way to make it more sensitive?
I drove a few rentals and on new cars brake s are super touchy, you barely touch the brakes and you already start slowing down fast.

Legender

You don't state the condition or how many miles?

What color is the brake fluid?
When is the last time you changed pads and what type of pads did you use?

PureDrifter

iTrader: (10)

Flush the brake fluid.
verify no vacuum leaks in/around the booster.
Adjust the Brake pedal -- Brake Master Cylinder pushrod


Then decide how it feels.

valex

Flushed fluid 2k ago, I will read up about adjustments that can be made, thank you!

YODAONE

Who "flushed" the brake fluid? If not Lexus (or for that matter, if Lexus) was the factory shop manual followed? Fluid type? A few extra steps with brake anti-lock brake actuator.

Did the problem develop after fluid was flushed? What are condition of wheel bearings? Pads? Rotors? Caliper seals? Flexible brake lines? Master cylinder? Vacuum booster canister? Vacuum check valve?

YODAONE

[QUOTE=valex;9489330]Flushed fluid 2k ago, I will read up about adjustments that can be made, thank you![/

Attached are Brake System Troubleshooting items (image from 1993 LS400 shop manual), 1999 LS400 Brake Booster Assembly Operations and Air Tightness Checks, Bleed Brake Line and Brake Actuator procedures.

valex

My 99LS has 207K miles. I said wrong, I didn't flush, I bled brakes, got over 6 little bottles of new fluid into the system Synthetic DOT4.
Rear wheel bearings changed just a month ago, new rotors and the pads were in great shape (OEM brand), so I reused them.
I am going to check the caliper piston rubber seals first.
It brakes just not abruptly as it should, I think.

YODAONE

You may want to check on compatibility of DOT4 with synthetic DOT4(unless you flushed every line and component) - its increased susceptibility to compression(silicone based brake fluid) and compatibility with brake component rubber seals....

Please share your findings.

djamps

Mine is the same way and always been. Plenty of brakes but braking doesn't *start* until the pedal is 1/2 of the way down. Hard braking I can push the pedal down so far I can't even get a toe under the pedal. I swapped master cylinder and bled everything but no change. From my research (assuming you don't have any obvious issues) it seems like it's just the way it is, there isn't anything you can do unfortunately.

Just to be clear... the brakes work FINE and I can lock them up no problem if needed... it's just long/mushy pedal travel for normal braking compared to other cars.

YODAONE

Part of the mushy feel is the body bracket to brake pedal pivot bearing and master cylinder clevis to brake pedal has an incredible amount of tolerance between components...which must be overcome before actual braking occurs.

For an engineered solution see;
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/820550-brake-pedal-clunk.html

I am in process of blueprinting the upper collar bearing ID to match the shoulder bolt. The Home Depot Shoulder Bolt was an improvement, but not perfect. Waiting for precision hardened Holo-Krome shoulder bolt sample before doing so. Will report results.

timmy0tool

iTrader: (7)

^ interesting!

and yes, i too experience long travel on the brake pedal and chocked it up to "that's the way it is". it is certainly not very assuring to drive after being behind the wheel on more modern cars.

djamps

For me, at least, it's more than just play up top. I don't mind the extra travel that much... but the mushiness of the brakes once kicked in bothers me. If I'm pointed down hill at a light in-gear and don't keep a steady foot on the brake (say I reach into the back for something) I've inched forward unknowingly.

My other car is a G35 with OEM brembos and stainless lines so maybe I'm spoiled, but maybe tossing on some SS lines could help. But even the wife's big SUV has much more responsive brake pedal....

700bones

Bleed the brakes. Make it easy on yourself and get speed bleeder valves to replace the stock bleeders. That way the pain in the a** job becomes easier in the future.

Still mushy for you? THen try replacing teh brake hoses with stainless steel braided lines:
http://www.lexls.com/tutorials/brake/SSbrakelines.html

Yamae

I worry about the trapped air in the ABS solenoids. You can't remove it without cycling those solenoids. There are totally 15 of them and you need an equipment which is capable to cycle them.

700bones

Only one way to find out --- pull the ABS fuse and see how it feels!