siaxazn

I just upgraded to ls400 4 piston calipers and got some new cheap cross drilled slotted rotors and rotex brake pads. After taking it out for a few runs the braking isnt as good as it should be. I have 2 other friends with sc's who have the same upgraded calipers but thiers feels much better. The problem is when I slam the brakes the car doesnt stop like it should, It should lock up and make the tires skid but mine just keeps going. When iI do this the brake pedal feels as if it sinks in more than half way. With routine driving and braking it feels ok.

my brakes never used to feel like this before the upgrade
I bleed the brakes 3 times. Still no improvement.
So now i suspect its one of 3 things

1. when i start the car and pump the brakes i hear air. It comes from the master cylinder area. is that normal? i never used to hear that noise before the upgrade.

2. I didnt notice anything leaking anywhere and the reservior looks to be at the same level as it was the pervious day. I'm thinking maybe im lose brake preasure when i slam the brakes or theres still air in the system or something.

3. Could my cheap brake pads and rotors cause this?

aliga

iTrader: (147)

you still may have air in the system?? not sure why you should hear air by the master cylinder?

vipsoarer

check for a leak on your brake booster line if its not that its most likely a seal on the brake booster. id check the line first then if its not that then move on to the booster. there should be a seal on the side facing the firewall that can leak air when they are old. if its not that u just gotta keep inspecting parts in that area. good luck

siaxazn

i dont really suspect it to be a leak in the master cylinder area since this only occurred after i swapped in the brakes. unless by some odd chance it decided to leak right when i swapped my calipers. But Could it be possible that I hear some air noise comming from there due to a preassure leak in the brake lines? The brake lines didnt really fit like they should have becuase i got 98 ls400 calipers and apprently the sc300 hose doesnt directly fit into them like for the 95-97. The part that doesnt fit is the metal hook(the thing that prevents the hose from moving when you torque the nut down) on the end of the hose that connects to the brake caliper. I couldnt find any ss brake lines for the ls400 95+ calipers so i just ordered some new 98 rubber brake lines. I'll see if that helps. also i ordered some speed bleeders so hopefully that will make sure i dont get any air in the system.

aliga

iTrader: (147)

the metal hook is just a holder, i dont think thats the problem.

mrshabo

it could be your brake pads.. if they are new and your slamming on them, they still have that first layer that needs to be taken away first before you see their true potential.

siaxazn

I suppose the fact that the brakes pads have not been broken in yet could be the reason why they dont lock when i slam the brakes. But i still feel like the pedal gets soft and sinks in more than it should when i slam the brakes. i'll change out the brake lines and rebleed the brakes with the new speed bleeders i ordered this weekend. if that doesnt work i'll see if my mechanic can find a leak or something. Thanks for all the help.

vredniykot

just break it in
give it 300 miles
if your brake lines are leaking you will loose your brake fluid after a few good slammings and your brake light would come on on the dash

new rotors and new pads = soft brakes
i went to midas once to get rotors turned and they installed new shoes while they were at it, the tech told me to 'take it easy' for first 2-300 miles, especially told me not to slam'em

siaxazn

i've installed new brakes and rotors in several occassions and i usually do break them in by not braking hard for the first 300 miles. but this time I got big brakes and I just couldnt help myself. Its just so much fun to have. Almost everyone who installed them has slammed the crap out of them when they first installing it. I slammed them so badly that at one point the brakes were smoking, 5 good slams could do that to it.

I think i read somewhere that there is another method of breaking in your new rotors and brake pads and thats to slam the crap out of them right away. I'm doubting thats true though but maybe it is.

Neo

iTrader: (3)

It is true.

Bed-in info

UpInTheLex

iTrader: (5)

Bleed your brakes again. Start on the passenger side of the car first. If your pedal squishes and you don't stop, you're compressing air before you compress the fluid. Theres still air in the lines.

Theres no need to brake them in past a couple moderate 25mph to 0 stops, and a good hard 40mph to 0. Thats all brakes need.

cheap rotors might crack or warp easier than other rotors, but they won't cause the symptoms you discribed unless you lubed them up with wd-40 or some 90weight gear oil first.

I'm sure your pads weren't contaminated either.

chances of master cylinder failure is very unlikely.

siaxazn

I did the upgrade last weekend and let the car sit there for a week and went to check the master cyclinder and the fluid level looked to be the same so i dont suspect any major leaks. So then i decided to installed new brake lines for a 98 ls400. and bought some speedbleeder bleeder valves to ensure no air was getting into the system as i was bleeding the brakes. I installed them this morning and bled the brakes. I'm pretty sure there is no air in the system and i noticed no leaks. I took it for another test drive and it hasn't really gotten any better. I mean my brakes arent as firm as my friends brakes who also have sc's and ls400 calipers. It stops fine with regular driving but when i slam on the brakes it appears that the pedal goes soft and drops too far down near the lower 1/4. it never used to do that and the car doesnt even come to a complete stop like its supposed to. on my friend sc's when they slam the brakes it just locks up and the tires skid a bit and the car stops and thier pedal still stays firm.

I broken in the new brake pads and rotors for over 150 miles now with no change.I really think it has something to do with the fact that when i pump the brakes I hear squeaking air noises comming from that black round box behind the master cyclinder. perhaps thats telling me theres a small pressure leak.

so i narrowed it down to a few things
1. my cheap brake pads or rotors are garbage and i should of went oem.
2. My caliper piston seals are bad. This would make the most sense since my issue only occured after the swap. when i got the calipers it came with pads there were worn down, i dont know if that may have caused any damage to the pistons? But i guess it may not have been a problem since these brakes have a brake pad sensor and i suppose the guy who orginally owned the calipers would have saw the light go on and would of replaced them.
3. Master cylinder may have a small leak. perhaps when i was pooring brake fluid in the reservior i may have damaged a seal in the master cylinder. highly unlikely but possible.

Well what do you guys think I'd really like to get this problem solved or i would feel like i did the upgrade for nothing since im not noticed much of a upgrade since my brakes aren't 100% right now.

aliga

iTrader: (147)

i doubt the seals are bad, if they were you would see fluid leaking.

UpInTheLex

iTrader: (5)

Check your technique with the bleeder. It's a two man job the way I do it. I have a friend push the pedal and build up force. Then tell him to hold the pedal all the way down. I crack the bleeder and shut it again after a little fluid leaks out. You'll hear air bursts. And i repeat the process as many times as needed to get a firm pedal. starting with the wheel furthest from the MC. You definately have all the symptoms of air in the system.

siaxazn

i bleed the brakes 3 times with a friend helping out. i have a friend pump the brake 10-15 times then i undo the valve and let the air out and some fluids. i repeated this 3-4 times for each corner. by the time im done only pure brake fluid comes out. And if i was doing it wrong and happend to have gotten air in the system. Im sure my new speedbleeder valves would get all the air out. If you dont know what they are they are replacement bleeder valves with a built in check valve that allow you to bleed the brakes yourself.

Basically all you have to do is:
"When it is time to bleed your brakes, you loosen the Speed Bleeder 1/4 turn and pump your brake pedal. When the pedal is depressed the pressure generated opens the check valve letting air and brake fluid out of the end of the Speed Bleeder. When you release the pedal and it returns to the up position, the check valve closes and prevents any air from reentering the system through the Speed Bleeder. When bubble free fluid is evident you close the Speed Bleeder. In the closed position it works just like your stock bleeder screw and prevents any brake fluid from leaking out.."

definately worth the money to get these if you bleed your brakes on more than one occassion.

I guess the brakes arent that bad they just aren't preforming up to thier potential. If anyone has any other suggestions on what it could be let me know. I just feel like the air noise(kind of has a squealing noise to it) i hear by the master cyclinder when i pump the brakes doesnt sound all that normal and perhaps thats telling me theres a small pressure leak or something. Is this normal? I never recall hearing it in the past.