1999 Lexus LS 400 No Power Brakes

AVB

MEMBER
1999 LEXUS LS 400
V8
2WD
AUTOMATIC
102,000 MILES

I'm helping my brother-in-law out on a problem he's having on a 99 LS400. The problem is that he basically is not getting any power brakes. The pedal is solid but has to be pressed really hard to stop the car. We checked pads today, which were good, and bled the system with no luck.

I started suspecting the brake booster and checked for vacuum and leaks. I can't see brake booster checkvalve so I'm wondering if it has one and whether or not it's even possible for the master cylinder to be suspect.

TIA

Monday, March 17th, 2008 AT 1:41 AM

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

To check the vacuum booster, pump the brake pedal with the engine off until you've bled off all the vacuum from the unit. Then hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If okay, the problem is in the booster and the booster needs to be replaced.

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Monday, March 17th, 2008 AT 5:52 AM