siaxazn

btw i just want to let you know after installed new ls400 brake lines. It is confirmed that the 98+ lines are different than the 95-97 lines. the metal hook that puts the brake line at the proper angle is longer on the 98 lines. So the stock sc300 lines or and the 95-97 lines will not fit since they are shorter. of course you can still bolt them in with out the hook in the correct position. but it just seams like its not all that great since its not at the best angle for the brake fluid to get to the calipers, dont know if that makes a difference or not.

and also they do not have any SS applications therefore i purchased new rubber lines instead.

SCV8

The reason the pedal travels farther is most likely because the new calipers have more volume with the added piston area.

SupraCoup3

are you sure?

siaxazn

i looked real hard but came up with nothing.

CleanSC

When you bled the brakes, did you ever let the level drop in the master cylinder? If the level gets too low, you pump air thru the master cylinder and now you need to bleed it.

I just installed the LS calipers on my SC and it went without a hitch. Everything bolted up just fine and it works MUCH better than the stock brakes. There's definitely a huge difference so you should feel it once you sort your problem out. If you can't feel much difference, something went way wrong somewhere.



Good luck, man.

siaxazn

does anyone know how to bleed the master cylinder? i beleive that may be my issues. the fluid level did drop close to being empty in the master cylinder. I bleed all 4 calipers to try to get any air out. But yet it still does not feel like 100% of the air is out.

UpInTheLex

iTrader: (5)

Bleed the master cylinder?? duude... you can't bleed the master cylinder.

CleanSC

UpintheLex...

No offense man, but when you give people the wrong info and then put the smiley like we're all stupid when you're the one that's wrong, it makes you look really bad.

Please know what you're talking about if you're gonna try to get smart. Other's that may need to learn are reading and don't need to read false information. Usually I'd just point out the wrong info and list the facts but your sarcasm changed that.

You can bleed the master cylinder, period. What happens when you get air in it? Sell the car? No, you bleed it. You may let the fluid level drop too low or install a new MC. Both rather common scenarios would require you to bleed to the MC.

Siaxazn: To bleed the master cylinder, get a friend to pump the pedal while you get under the hood:

a) Disconnect the brake lines from the MC
b) Have your partner press the pedal down. Fluid will come out so have a rag under it as you don't want this stuff on your paint.
c) Cover up the holes where the lines were connected with your fingers while your partner releases the brake pedal.

Repeat steps b and c four times or so. And then reconnect the lines.

Always remember when bleeding your brakes to check the MC level. Letting it go dry just adds more mission to your project.

UpInTheLex

iTrader: (5)

It's not possible by practical means to re-tighten the line at the master cylinder without introducing air to the system.

Besides, Bro i'm talking about bleeding air from the master cylinder, not fluid. How is air going to get trapped in the master cylinder? A full pedal depression will insure no air is in the master cylinder. If you let it run dry then you will push air into the lines. If you're going that route.. A full system restart, ensuring all the air is cleared from the master cylinder to the caliper, I think my way is better than the one you described. You leave those lines you described connected, no reason to disconnect them. Do everything at the caliper.
Have a friend fill the cup to the top. Biggest mistake you can make is letting it run dry. Open the bleeder to the left front caliper to make it easy, it's the first place the fluid ends up .. Have a buddy stay by the cylinder with a whole jug of brake fluid keeping it full. Push the fluid/air through the line and out the bleeder If you have two guys then you should have no problems using regular bleeders. These speedbleeders might be part of your problem. I don't know anything much about them. Run a can of fluid through there and you know there isn't any air left.
Only other advice is start tightening the bleeder screw before you reach pedal 100% depressed. At about 75%, Start closing the screw, so you're done at 95%. And pump it way up to the highest pressure you can get, then push hard and tighten that screw at 95%. Again that insures theres total fluid contact. .

Following a good bleeding procedure go back and do it again. Bleed in a sequence starting from the right rear, left rear, right front, left front. .
o.k. one more tip.... tap the calipers with a rubber mallet to insure that no air is clinging to the walls of the caliper.

Dude, I know what I'm talking about.

Rolling my eyes.. I don't know.. I guess I really wish we could correct this problem already. I've been through everything you're saying before...all the symptoms, same problems in my time as a mechanic and chassis guy.

CleanSC

I've done this exact same method and it has worked perfect for me. While your method may work, it seems to be a waste of time and brake fluid just to pump air bubbles at the MC all the way thru feet and feet of lines, the ABS actuator, more lines, and finally the caliper. Why? The bubbles are at the MC and can be purged right there.

And if it was so impractical, Toyota should be notified because it's in all their repair manuals:

UpInTheLex

iTrader: (5)

Ouch!

I stand corrected, i'm gonna roll the eyes at myself

I'm krunk at 1 in the moanin... humboldt county sylez///


holla, 8 in the morning she'll be calling a cab, 9 in the moanin talking bout the fun she had. Holla

siaxazn

thanks for the advice. I'll try to bleed the mc tomorrow and see what happends. I'm 99% sure im bleeding the lines correctly. I tried bleeding it the regular way like 3-4 times. Then after that i bought some speed bleeders and it did help a little bit. It makes it much easier to bleed and it feels like less air gets trapped that way.

siaxazn

After some research i kind of think maybe my brake booster has gone bad. Everytime i press the pedal I hear a hissing noise, comming from the round black box behind the mc. I read in a post that, it means your brake booster has gone bad. Yet I dont have the symptom of having to get a work out to get the brakes to work. Can anyone confirm if the hissing noise is a bad brake booster? the noise only apeared after i did the caliper swap. so i dont know what to think.

the post about it is over here
https://www.clublexus.com/forums/sho...ooster+hissing

CleanSC

If you suspect a leak at the booster, do the following test to make sure it's airtight:

Start the engine for a minute or so and shut it off. Pump the pedal as if you were braking several times. On the first pump it should go down the furthest. The second pump it will go down a little less, and the third time even less, etc, etc. If it acts like this, it's airtight and good.

Second test:

Start the engine and then press the pedal firmly. With the pedal still pressed, shut the engine off. Hold the pedal at the same foot pressure for 30 seconds with the engine off. If it doesn't move, your booster is airtight.

If you past these two tests, your hissing is coming from somewhere else.

However you say that you don't feel that the brakes are any harder to press which makes you believe the booster is fine. If the leak is small, it might still allow the booster to provide enough assist to make the brakes easy to operate while at the same time making the hissing sound.

It would take a total failure of the booster to make the pedal harder to press (like if the engine was off, we all know how hard they get to press).

If it is in fact the brake booster that is leaking, I would guess what happened was while you were bleeding the system, you may have pressed the brake pedal to the floor. The booster and MC aren't used to hyperextending into these areas even tho they are designed to. Under normal circumstances they should never be in these areas so it may be that a weak booster diaphragm could be stretched just enough at this point to cause a tear or leak. This would explain why it happened during your brake upgrade.

Just a theory, don't hold me to it.

Run all the tests and see what results you get. Have you tried to hear where the hissing is exactly coming from? Behind the booster, from inside, the vacuum line?

Let us know.

Lexs400

interesting thread since I've been experiencing similiar problems with my 93ls400. but the difference is that everything is stock and i didn't upgrade my brakes to different ones.
i've tried pretty much everything that has been discussed in this thread and more to the point of changing m/c, booster, callipers, pads and rotors.
still a pedal that engages to the point of a hard pedal but midway towards the firewall.
the last action all the troubleshooting guides point to the adjustment of the pushrod between the master cylinder and the brake booster.
while in the case of brake upgrades, it is unlikely but worth the effort during the process of elimination.
I have taken note of the manual page on how to bleed the m/c. very informative.
could someone please provide the manual page on how to adjust the pushrod as well.
maybe it will be different for the SC than the LS400 but nevertheless the process should be similar and will help me in this task.
thnx.