1992 Buick Lesabre 92 Lesabre brakes

COMAROSCO

MEMBER
1992 BUICK LESABRE
6 CYL
2WD
AUTOMATIC
140,000 MILES

I have a 92 lesabre, and while driving the breaks became soft and the pedal went to the floor and it became hard to break. I checked all the breaks and lines but did not find any thing wrong. So I put in a new master cylander, and bled everything from back to front many times with no success. I then replaced the power brake air valve and the pedal still goes to the ground. Before putting in the new master cyl I checked the booster and all seemed fine. The only thing that I noticed was everytime I push on the pedal it makes one click sound and also on the way back up. Looking under the dash its a box with a buton that the break releases when you push them down. Dont know if it has anything to do with it but thought I would mention it

4 Replies

JACOBANDNICKOLAS

MECHANIC
108,192 POSTS

Hi:
The box you're talking about sounds like the brake light switch. I doesn't have anything to do with the pedal. DId you bench bleed the new master cylender? Also, have someone press on the brakes and watch both rubber brake hoses on the front wheel. Sometimes they get weak and expand rather than forcing the fluid through to the calipers. If the car has 4 wheel disc, check the rear also.

Let me know what you find.

Joe

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Friday, November 14th, 2008 AT 4:58 PM

COMAROSCO

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8 POSTS

Thankyou for the reply, and yes the master cyl was bench bled x2. The front has discs and the rear has drum and all seem to be fine. I bled the car both with the engine off and on but still nothing. When I push on the breaks the master cyl does show that it has pressure. When the car is off the break pedal stiffens up nicely but as soon as you start the car it sinks to the floor. I'm running out of ideas and your input would be helpful.
Thanks, Josh

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Saturday, November 15th, 2008 AT 10:37 PM

JACOBANDNICKOLAS

MECHANIC
108,192 POSTS

Josh, Does the pedal go all the way to the floor? Are the brakes working at all? When you replaced the master cylender, was there an adjustible push rod in the booster? Finally, did you check the rubber brake hoses and are the rear brakes properly adjusted?

As far as the brake pedal being firm when the car is off, that is normal because you loose vacuum assist from the engine.

Please answer my questions, and we'll go from there. Also, get someone to help you test the rubber brake hoses on the front. Also, is there any evidence of brake fluid leaking anywhere?

Joe

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Saturday, November 15th, 2008 AT 10:56 PM

COMAROSCO

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8 POSTS

The breaks weakly work when the pedal in barely on the floor. They have to goto the floor and maintain pressure to stop slowly. When I installed the new Master cyl the rod did not seem to need to be adjusteed. In addition the rear breaks seem to be at the right adjustment. I'll start over and check the booster rod. If you could think of any more info please email. Thanks, Josh

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Monday, November 17th, 2008 AT 11:59 AM