DshngDaryl

If we disconnected the wiring harness to the brake booster, would that simulate the situation? Or is it because there is a failed "O" ring that lets air into the system, it is not the same?

It would be interesting to see if anyone was "Brave" (or possibly stupid) enough to disconnect the booster harness and see if they can stop their car.

I too wonder if it is Total Brake Failure, or just Manual Brake Resistance. (My 76 Buick made me REALLY STOMP on the pedal to stop)

DshngDaryl

Is this the post where Lexus pulled the crash data from the computer to see what the brakes were doing? Or is that a different post? This issue has been discussed in a couple different threads

Bgw70

I am on it, JK…not gonna be me but I did want to add. When we bleed the brakes, the process is the normal way for the front, pump the pedal, hold and open the caliper bleeder screw.
the rears are different, just turn the key on and hold the pedal down, release the bleeder screw and the fluid will continue to flow until empty or the bleeder screw is closed…why, because of the pump.

I still think it could be the brake booster or the MC piston O-ring failing.

SC430fun

I have not experienced this in my Lexus thankfully and hopefully I never do but the brake system in these cars is different. Most cars you can stomp on the brakes hard even if the power booster is out and it will push the rod in the master cylinder and stop the car fine. I had an 84 prelude the car refused to die until somebody in a brand new Mercedes totaled it and they were totaled as well. But what happened is I was coming to a stop normally and I heard a loud pop and the brake pedal got stuck and I realized my power booster just busted, and stomped on it harder and it was fine. I’m not a small dude and I have a size 15 foot so I have plenty of leverage in my legs and weight in my feet. In fact I drove the car like that for the rest the time until it was totaled. The power steering pump was leaking so I disconnected the power steering belt and drove it all manual with the manual transmission and was happy with it. However not everyone is the same and some people need the power assist.

The mechanism in our cars is quite different. When I first started hearing stories about this with the brake system failing I figured why the hell people don’t just stomp on the brakes super hard and then I started looking at the diagrams earlier in this thread or maybe it was another thread that was put up and it’s a completely different design. Stomping on the brakes extra hard in this situation, a lot of the effort gets lost in the system and doesn’t go straight through the hydraulics pushing fluid to the calipers.
I’m not sure if it’s the little motor inside that builds up pressure or it’s a seal or possibly both that causes this. I think eventually it will be figured out, and it’s some thing that we can deal with in a preventative fashion with maintenance to hopefully keep it from ever happening on our cars.

I don’t think most people will have an issue stomping on the brakes extra hard if this emergency situation were to arise, but with the design of it where you have an extra amount of complicated hardware, it’s not the same as many other cars most of which don’t have this system.

I hope it never happens to me or anyone else I can always downshift but if this issue comes up during an emergency stop you are probably ****ed. It’s definitely a flaw of some kind with the design and should have been more redundant. The way Lexus responded to the person and investigated with their car tells me that they were taking it seriously, but were automatically in damage control mode more or less by making excuses that it’s an old car, etc.

Harold57

You could try disconnecting the booster harness while in Park and see what the pedal feels like.
Note that I said "you could".

SC430fun

all this talk about this I think I’m going to try it and will disconnect the harness from the booster and any other wiring I see. I’ll do it in a large parking lot where I don’t have to worry about hitting anything. My car is going to be taken apart quite a bit in the coming weeks to have the Lextreme 2800 stall torque converter done with an external trans cooler, and I’m going to have the transmission pressure mod done as well and a full trans service with my 2006 with 6 speed auto (sealed trans unfortunately with no dipstick!). At the same time I’m going to have my starter changed out because it’s been clicking and sometimes it takes two or three tries before it starts normally and I’m going to nip that in the *** before it goes bad completely. Also going to have the AC compressor receiver dryer and expansion valve changed out with the AC lines and then the system recharged, and I may likely have power steering lines and possibly the power steering pump changed out at the same time as well because it’s dribbling fluid and I don’t want ANY leaks on my SC. Probably about 2000 to 2400 of work there at Lextech in Los Angeles owned by an owner that loves these cars and has an sc300 with a big turbo - couldn’t think of anyone better to do the work on my car. They will swap in the quantum ECu

at that point every leak should be taken care of the car can be buttoned back up and be driven normally again for the rest of the next year while I build up the extra engine I have sitting on the floor of my garage in front of my car because once that engine goes and all of the new accessories and parts I put on my current engine will just transfer over to the new engine that has been enlarged to 4.7, 5.0 or 5.2 I still haven’t decided yet since I will need to use a 2UZ iron block that’s sleeved if I go the 5.0 or 5.2 route. There is a tundra 4.7 engine kit I may use with all forged internals that is 2500 for everything from JC Whitney or one of the other giant suppliers , and at least I know I can use boost again.

I know this is a completely different subject I keep bringing up here but I’m about to dive into it headfirst and I’m going to be opening an engine build thread in the main forum for these cars so people can follow along with my build and we can finally put to rest the debate on just how much these engines are capable of putting out naturally aspirated when they are built up properly I guess is probably 380 hp or so when an AA if I keep it at 4.3 or 4.7, or around 400hp if I go 5.0 or 5.2.

Bgw70

it sounds like you have some awesome plans ahead…

I may be wrong but I thought the pressure mod switch only worked on the 2002-2005 five speed…

you could get the starter replaced at anytime since it is located under the intake manifold…such a crappy place to put it

Also, getting the PS leak corrected is smart because it usually drips on the alternator and will ruin it.

let us know how everything goes

SC430fun

[QUOTE=Bgw70;11094272]it sounds like you have some awesome plans ahead…

I may be wrong but I thought the pressure mod switch only worked on the 2002-2005 five speed…

you could get the starter replaced at anytime since it is located under the intake manifold…such a crappy place to put it

Also, getting the PS leak corrected is smart because it usually drips on the alternator and will ruin it.


thank you originally the hose from the reservoir to the pump was leaking it seems to be a problem on all of these cars that are using the factory clamp it gets loose through time. I went ahead and slid the clamp down and added a screw clamp and it took care of the problem but there is a leak coming from that area now and it’s a new one and I’m suspicious it’s coming from the pump so while I have everything apart I’m doing the pump with all of the lines. I don’t want even a slow leak anywhere on my SC!

jimisbell

I have never owned a car that the starter wasnt in close proximity to the exhaust. I dont think that is a problem. Even my cars from the 40s and 50s have the starter under the exhaust pipe! Its the best place for it.

Bgw70

Same for SC430

You Tube

GmanSC

Darn, I hope that I never have to replace that starter.

Wilson2000

What ruins starters is long episodes of cranking before the engine starts. Every Toyota I've ever owned has started immediately upon turning the key. So, I wouldn't worry too much about your starter failing unless it has been abused. I'm not saying it will never happen, but the odds are small compared to vehicles that over-tax the starter.

mw325

Last weekend, I replaced the entire brake assembly 47050-24060 in my wife's 2006 SC430. Very appreciative of the information I gathered in this forum. She experienced the alarm/loss of brakes just as she was pulling into a grocery store parking lot. As has been noted, there is some braking ability, but not much without the booster. Anyway, after looking at a number of used units, I decided to order a new unit from a part's supply house. I was pleased when the box arrived a few days later from a Miami Lexus dealership, in a new, sealed box shipped from Lexus in Japan. $1,294.00 w/shipping. That's a lot of money, but I figured I would only have to spend about $12 bucks on brake fluid and nothing on labor. Installation went well and the car works great again. My wife does a lot of freeway driving and I didn't want to risk another failure at a higher speed.

DshngDaryl

Sounds like solid logic to me! Welcome to ClubLexus!

Wilson2000

WTF Lexus?