Symptoms of faulty brake master cylinder & booster?
02-23-10 | 03:02 PM
#33
Intermediate
Joined: Feb 2009
Posts: 454
Likes: 4
From: KY
it really depends on what type of failing the master cylinder had.
most mastercylinders fail because the seals on the inside are worn out. this means instead of holding pressure, its bypassing and leaking fluid. this causes the pedal to fall to the floor.
the problem with the GS, is that the brake master cylinder AND the brake booster are considered as 1 unit.
from my basic knowledge and what i could see, the GS has a redundant system, the brake fluid resevoir has 3 valves. 1 valve is a return valve, 2 valves go down into core which the brake pedal pushes. each valves fills each system all activated by 1 push rod core. they both feed into the brake booster that is attached to the side, which then pressurizes the fuild (hence the short curve bent brake hard line). this feeds into the electronic brake distribution system, which then sends it out to 4 hard brake lines.
im sure its more complicated than that, but thats what i see.
the test preformed to see if your brake booster is working or not is, while the engine is off, you pump your brakes until the pedal hardens. then with your foot on the brake, you turn ur engine on. if the brake booster is working correctly, the pedal should fall to the floor.
the test for a brake master cylinder failing is to hold ur foot on the brake pedal firmly. if the pedal begins to sink, then the seals on the master cylinder are failing and not holding pressure.
it may just be pure coincidence that ur brake master cylinder failed soon after the brake job. you did say u drive a 99. which means 11 years of use, which means it was bound to eventually need replacing.
the only possibly harm i could see have been done is if the mechanic pushed the brake calipers back forcing the dirty brake fluid back up into the system instead of bleeding them out from the caliper. this is all speculative. especially not knowing the history of ur cars maintenance.
and ill take pics of that plug sensor tommorow. but for now, time to get stupid in the olympic celebrations! couldnt even head out to see deadmau5 last night! =(
most mastercylinders fail because the seals on the inside are worn out. this means instead of holding pressure, its bypassing and leaking fluid. this causes the pedal to fall to the floor.
the problem with the GS, is that the brake master cylinder AND the brake booster are considered as 1 unit.
from my basic knowledge and what i could see, the GS has a redundant system, the brake fluid resevoir has 3 valves. 1 valve is a return valve, 2 valves go down into core which the brake pedal pushes. each valves fills each system all activated by 1 push rod core. they both feed into the brake booster that is attached to the side, which then pressurizes the fuild (hence the short curve bent brake hard line). this feeds into the electronic brake distribution system, which then sends it out to 4 hard brake lines.
im sure its more complicated than that, but thats what i see.
the test preformed to see if your brake booster is working or not is, while the engine is off, you pump your brakes until the pedal hardens. then with your foot on the brake, you turn ur engine on. if the brake booster is working correctly, the pedal should fall to the floor.
the test for a brake master cylinder failing is to hold ur foot on the brake pedal firmly. if the pedal begins to sink, then the seals on the master cylinder are failing and not holding pressure.
it may just be pure coincidence that ur brake master cylinder failed soon after the brake job. you did say u drive a 99. which means 11 years of use, which means it was bound to eventually need replacing.
the only possibly harm i could see have been done is if the mechanic pushed the brake calipers back forcing the dirty brake fluid back up into the system instead of bleeding them out from the caliper. this is all speculative. especially not knowing the history of ur cars maintenance.
and ill take pics of that plug sensor tommorow. but for now, time to get stupid in the olympic celebrations! couldnt even head out to see deadmau5 last night! =(
02-23-10 | 10:12 PM
#34
Driver School Candidate
Joined: Feb 2010
Posts: 7
Likes: 0
From: MI
Just a quick question for you guys...
would a master cylinder off an '04 GS300 be compatible with my 99 GS300
Also, should I ask the guy at the salvage yard to ensure that the booster and the electric motor are included; or should I assume that they will all be pulled off with the unit as one. I ordered a master cylinder online brand new only to receive it and realise that there was no brake booster or motor included with it.
would a master cylinder off an '04 GS300 be compatible with my 99 GS300
Also, should I ask the guy at the salvage yard to ensure that the booster and the electric motor are included; or should I assume that they will all be pulled off with the unit as one. I ordered a master cylinder online brand new only to receive it and realise that there was no brake booster or motor included with it.
02-23-10 | 10:17 PM
#35
Do you need one? I have a one that's in very good condition.
Check here if interested.
https://www.clublexus.com/forums/2ge...oem-stuff.html
Check here if interested.
https://www.clublexus.com/forums/2ge...oem-stuff.html
05-08-10 | 04:55 PM
#36
Driver School Candidate
Joined: Oct 2008
Posts: 41
Likes: 0
From: california
my bmc went out about a month ago and i just rebuilt it today. But i still have a problem. when i drive it the front brakes work but the back doesnt. when i pull off the back wheels to bleed, nothing comes out? does anyone know why this happens? abs, vsc, e-brake light all on and that annoying beep is on to.
i dont get it , just rebuilt the thing and the fronts bleed but the back doesnt?
and the brake pedal is stiff. im close to just deleting abs and taking out my bmc and just setting up my rx7 style bmc
i dont get it , just rebuilt the thing and the fronts bleed but the back doesnt?
and the brake pedal is stiff. im close to just deleting abs and taking out my bmc and just setting up my rx7 style bmc
Last edited by 98GS450; 05-08-10 at 04:59 PM.
05-28-11 | 10:19 AM
#37
Can anyone document the difference between that one sensor off the brake booster? I read someone mentioned that they can use the 01+ on the older model by just modifying the plug.
I have an 01, someone also mentioned that the problems were resolved for 02 and up, it that true?
I have an 01, someone also mentioned that the problems were resolved for 02 and up, it that true?
05-30-11 | 10:41 PM
#39
01+ has one sensor that is different. You can remove the sensor with a 30mm and replace with the older sensor. You can also cut and splice if you want to keep the newer sensor. You will need a deep socket.
Changing it is not so difficult.
Changing it is not so difficult.
05-08-17 | 05:00 AM
#40
Pole Position
Joined: Jun 2013
Posts: 220
Likes: 12
From: Germany
does anyone know where i can find the electrical plugs for an '01 gs 430 master cylinder?
i would like to have both connectors, so i basically can run an extension with a lamp, so i know exactly how often the pump is running, as i am suspecting low nitrogen pressure.
i would like to have both connectors, so i basically can run an extension with a lamp, so i know exactly how often the pump is running, as i am suspecting low nitrogen pressure.
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