OG Dada

iTrader: (10)

Here are my symptoms;

- 1st pump is normal
- when first pump of the pedal is done halfway, then followed by a quick 2nd pump when slowing down, brake pedal becomes stiff and can't push all the way down and car slows down very very slow with a lot of effort to push the pedal
- when symptom 2 happens, there's a distant sound of 'hiss' sound coming from the brake pedal area, like air is leaking
- doesn't happen often when driving freeway speeds, usually happens when slowing down and about to come to a stop or backing out like of a parking spot

Did a brake fluid flush a few weeks back, replaced all 4 rotors, did the LS brake caliper upgrade already to try and remedy this. Checked brake booster vacuum lines, even replaced the OEM clamps to universal ones and the symptoms are still the same, and I believe even became worst even though the brake bite is better than before.

- brake fluid was flushed a year and a half ago, but when i did the flush this time the fluid was dirty and a lot of moldy stuff on the reservoir walls
- no loss of brake fluid ever since
- slide pin in the rear became stuck, but greased up and fixed now
- before new rotors, all rotors were already bad - past their minimum thickness

Checks I've done;
1. Turn off the engine - pump brake pedal, it becomes stiff like building pressure, but there's a small pop sound when I hold the pedal, and pedal goes 1/4 down but not all the way down.
2. Engine turned on - bend the brake vacuum hose a little bit, and air is coming out - which means booster holds air/pressure.

Any help is appreciated. If you need any more info, just comment and I'll keep checking this thread throughout the day in my phone while I'm out. Thanks!

OG Dada

iTrader: (10)

Ok this is the first time this symptom happened ever since I've had these braking issues. I was trying to slow down to get into a parking spot(just right now) then the engine started to bog down then it shut off while the brake pedal became stiff and hard to go on full stop.

Question: there's a valve in the brake booster line, is it possible to get clogged? If so, how can I check? Someone please help.

xspsi6

iTrader: (31)

Sounds like a bad booster which is odd but can happen I suppose.

OG Dada

iTrader: (10)

Not that I don't trust you, I just wanna eliminate the master cylinder as the culprit, is there any particular reason why you think it's the booster and not the master cylinder? I'd go for the master cylinder anytime being way cheaper than the booster, but I'm pretty sure I can buy a used booster since its not that common of a problem, right?

xspsi6

iTrader: (31)

Usually when the master goes bad the pedal will go to the floor when you apply pressure and will sometimes roll through a stop light plus you would be pumping it constantly trying to regain pressure.
I have only heard of a booster on a sc going bad once which happened to my friends 200k mile old 93 sc300.

OG Dada

iTrader: (10)

I completely agree with you. My SC is 1500 miles shy from 200k. I'm just so stumped because when I turn the engine off and pump the brakes, it still holds pressure, and I just noticed today that my brake fluid is all dirty and grimy again....

xspsi6

iTrader: (31)

Do you still have rubber brake hose? If so get rid of them asap for braided ones as the rubber is most likely the cause of the black or dirty fluid coloring due to basically rotting away from the inside out.
I use these and have for my last 3 Lexus cars so they are good to go! http://www.ebay.com/itm/Stainless-St...d694f6&vxp=mtr

OG Dada

iTrader: (10)

I did braided stainless steel(Goodridge) when I first got my SC 'cause the rubber had cracks everywhere.

xspsi6

iTrader: (31)

There could be residual build up in the brake cylinders on the calipers from the rubber lines so you may have to flush it a few more times yet.

sidwin

If u replace the booster you should replace cylinder too. I learned this the hard way. Replaced only the booster then pedal was super soft. My mechanic said when booster goes out, it can contaminate master cylinder by breaking the seal.

xspsi6

iTrader: (31)

This is true^^

sidwin

sad thing is aftermarket booster just isn't the same as stock but i wouldn't pay for overprice stock one... your brake engagement point is going to change. If you're not road racing that isn't going to be a big deal but for my track car it made heel toe a major PITA.

OG Dada

iTrader: (10)

This is getting harder and harder... A lot of people I personally know have different views based on my symptoms. I think I'll replace the booster first, if that doesn't fix it, then ill replace the master cylinder, if it still doesn't fix it, then ill replace the entire car. Lol Anyways, do you guys really think its the booster at this point?

xspsi6

iTrader: (31)

Honestly it is good measure to replace both at the same time as at the shop I worked at we would always do both at the same time or we would not do it at all (my boss was a stickler for doing things right the 1st time) You could source a good low mileage booster and just put in a re man master? I have a friend that has a spare as he bought the wrong one but I would need to know if it's a 2 or 3 bolt unit? That is if he has not e-bayd or sold it already but I can ask for you.