PHML

iTrader: (33)

have you tried bench bleeding the master cylinder unit?

SorrGwa

iTrader: (1)

yup, i did exactly that after i installed the rebuild kit.

the rebuild kit comes with the front brake pistons, the rear brake piston, the sleeve w/ O rings, and the C clip that locks the whole thing in place.

hopefully ill get the other brake master in on friday.

SorrGwa

iTrader: (1)

ok finally!!!

got a brake master cylinder off a local wrecker. 600 CAD.

heres my day, started at 10am, finished just now at 6pm.

Took out my old brake master cylinder/booster. and compared it to the one i got from the wrecker (from a 00 GS400). good thing i did! every plug matches cept 1!. there is the 3 black plugs on the side of the BMC, then one just under the resevoir that is a black one that looks like it connected to a huge hex nut. THIS ONE! the BMC i got had 3 prongs in a triangle. the one i had was 3 prongs in a line like - - -.

so i decided, swap over the booster and give it a try! NOPE, utter failure, which means the BMC kit from lexus SUCKS! i did some searching, and found out the MR2 guys have a similar problem with the BMC kit that toyota provides them. most of them swap to a toyota tacoma BMC.

so what am i to do? no choice, take it all apart. take the resevoir out, take the booster out, take the mechanism that attaches to the bottom of the BMC that his held in place with 6 gold colors 12mm bolts. after that, i was able to get the core rectangular piece on a vice (carefuly with rags so u dont scratch it up) and remove that sensor to swap over.

put everything back together, added fluid, turns on system to pump a few times... ABS BEEP??? VDC ABS MOUSE lights all on, once the booster charges up again, the beep goes away. crap what is this????

bleed the system, major air, all 4 corners! so far no beep anymore and no VDC but its late and my back hurts from working under the dash.

will test drive tommorow to see if the car is really running like a champ.

ill do this again later when i do the ls400 swap, again. the reason why i didnt do it now was because i havent painted the new caliper yet.

anyhow, moral of the story, use the lexus brake master cylinder kit under ur own discresion (sp?) i was careful in my install but it didnt fix my issue. maybe ill take apart the old BMC just to see how and if i installed anything wrong.

will update.

rgarjr

iTrader: (1)

Are you saying that the 99' MC have 1 different plug than the 00' ones?

PHML

iTrader: (33)

good luck...take some pics if possible.

-Future-

I think because his was a gs300 and he purchased a used one from a gs400. That may have been the difference between the plugs. maybe?!

SirBev

iTrader: (1)

This sounds like alot of profanity was said when it went back together and didn't function like it should...good luck man

-Future-

my 2000 GS 300 has been doing the "babies screaming" act in the morning during start-ups. I feel the pulsing vibration of the screams through the brake pedal as well. I popped the hood and realized the sound is coming from the master cylinder unit, maybe the abs pump or booster. So I found one on ebay today from a 2001 GS 300 (pulled at 73k) for 300. So I'm hoping it's plug and play and will fix my problem. Then onto replacing an O2 sensor and steering rack bushing kit. I've been having that "something doesnt feel right" feeling with my lexus lately, not handling as smooth. So I'm hoping these adjusments especially the bushings help me out... I'll keep you posted on the master cylinder swap.

I'm going to ask my local STS how much to swap it out, or maybe a mechanic friend.....Not sure if I want to tackle this alone....Its my daily driver...Anyone in NJ have exp. with this?

rgarjr

iTrader: (1)

Yep, I had the same horrid problem with mine making that annoying sound. I think it's the ABS pump that makes it.

Anyhow swapped out Master cylinders and it's all good. This seems like common problem that Lexus should have re-called a long time ago.

GS300TK

I recently got the brakes done on my vehicle; rear and front pads and rotors. Apparently two of the calipers were jammed so the mechanic loosened those up. About a week later I was stopped at a light and all of a sudden my
ABS, VSC, VSC off & Brake lights came on with a loud beeping sound.

The brakes were still working so I pulled in and parked it. After pumping the pedal a few times, it became very stiff and I lost 95% of my braking power. The lights and beeping sound were still on.

I got the car into a mechanic and after inspecting the brake lines, fuses circuits, relays he concluded the power brakes; master cylinder had failed. He affirmed this by hitting the unit with a hammer a few times getting it to temporarily work. (according to the mechanic, the motor component of this unit is gone)

My first question is; do the above symptoms fall in line with a master cylinder failure?

Secondly, if the master cylinder has failed; could it in any way be due to the initial brake job done a week prior to this incident.

Also, If my master cylinder has failed are there any special procedures/precautions that he shoudl be aware of in replacing the unit.

Finally, I was able to find a master cylinder off a 98GS300 for $400. THE OES part is available online for $1100. Woudl it be safe to go with the used part on the vehicle; or woudl I be better off investing in a new one?

Any help would me much appreciated.

btw my vehicle is a 99GS300

rgarjr

iTrader: (1)

Well of course getting a brand new one will be better than getting a used one but, the only drawback is its an expensive route.

Don't think a brake job would do any harm to the motor on it.

SorrGwa

iTrader: (1)

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! =(

GS300TK

Thanks for your prompt response and all your help.

I will be going into the shop tomorrow and will check to see exactly which component has failed; the brake booster or the master cylinder itself... regardless of which one it is though, from what I understand the whole unit will have to be replaced.

One other question, since I am already getting the mechanic to change the BMC; would it be advisable to get a brake fluid flush done?

SorrGwa

iTrader: (1)

the BMC is one whole unit. lexus does not sell the booster and the BMC seperately.

you have to get a fluid flush done regardless when you change the BMC. you are detaching and reattaching the brake lines which introduces air into the system.

PHML

iTrader: (33)

flush it baby...flush it!!!