I just bought a 98 LS400 with 120k. The car is in excellent condition but there's something wrong with the brake system. When I press the brake paddle it goes half way in and becomes hard like a rock and the car won't stop. The previous owner gave me a paper from her mechanic that said that the car needs Brake master cylinder and brake booster, how often does the master cylinder and brake booster goes out on these cars. I've owned LS400 with 200k but never had master cylinder and brake booster issues.

 

Random. I had to replace a brake booster on the Maxima at 160K miles, a master cylinder on the Cressida at 120K miles.

 

POSSIBILITY your rear seal in the M.C. COULD have a leak that's pooling in the brake booster. Causing the rubber diaphargm to deteroiate, in the brake booster. Not allowing the brake booster to be an assistance. Does the brake pedal travel to the floor when applied?

 

No it stops half way and becomes hard and the car keeps moving.

 

ABS LIGHTS? How did the car drive before? or Has the car like that? This could be a tough call. Maybe a brake push rod is binding up, not allowing the brake piston to be fully engaged. If your handy with some tools and a shop manual, get in there a take a look. Brakes is something you don't want to take lightly.

 

The Gasket between Brake Booster and Master Cylinder was split open and it was sucking the air. Also the Master Cylinder was out. Thanks for the advise snake

 

i just had the same problem last night. I had to use the emergency brake to bring it to a complete stop. So, just wonder if you replaced your Master Cylinder with new or used one. Or rebuilt it? thanks. And do search button does work!

 

never heard of someone who actually opened up the booster.
Is the diaphragm a replacement part from Toyota or whole unit only?
Prices?

 

booster and cylinder a sold separate, booster cost around $735 and M. C. around $305. you can reuse the valve between M.C. and booster. Booster comes with brake fluid container as one unit.

 

So which one was bad the booster or master ? Or just the gasket connecting the 2 parts was leaking . I guess I need to see an expanded view to conceptualize this fix .

 

Sorry to bump this guys but i think im suffering from a similar issue. My pedals stiffens up with every pump i do with the car off, but the pedal does drop down where the car starts on with my foot on it. When the car is started up from a cold start, the rpm stays high at like 1.3k which is normal .. it drops down to 1.1k ish ..only to go back up to 1.3k and stays there unless i drop the car into gear... so im guessing its a vacuum leak from the brake booster? When im at a red light, the car makes a surging "vrrr" noise , guessing its a bad brake booster? thx guys.

 

check this out
http://home.student.utwente.nl/gombe...us/lsrm/Brake/

for brake master cylinder inspection try this
http://home.student.utwente.nl/gombe...rake/br-18.pdf

 

would a brake booster vacuum leak cause poor gas mileage?