Mechanics

CHEVY BRAKE PROBLEMS

1997 Chevrolet Astro

Brakes problem
1997 Chevy Astro 6 cyl All Wheel Drive Automatic 110000 miles

My Astro's brakes have an odd, but intermittent problem. Occasionally when I try to stop, they will make a groaning sound and I can feel the pedal push back against my foot and the van doesn't want to stop. If I continue to push on the pedal, you can hear a thump and then the van will stop short. A couple of times when this has happened, the pedal went all the way to the floor, the brakes released and the van started forward more quickly as the idle speed kicked in. I've replaced the pads, rotors and calipers as well as bled the lines. Do I need a new master cylinder or sensors, or what?
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Chphoto1
July 17, 2009.




Suspect a faulty brake booster

Bluelightnin6
Jul 17, 2009.
Ok, based on the reply, I suspect a faulty brake booster. I've looked over the diagram and pictures and feel pretty confident about replacing it. I've priced Astro brake boosters online and they're about $275. Is there a way I can test the one I have and make sure that's what I need before I put out the cash?
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Tiny
Chphoto1
Jul 18, 2009.
Sure, to check the 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.

Bluelightnin6
Jul 18, 2009.
I put on the new booster, and the power steering works better than it has since I bought the van, but now the brake pedal goes all th way to the floor and won't come back up.
I had to take out the master cylinder to get the old booster out and the new one in, so I assume the lines need bled, which I'm going to do in the morning, but the pedal to the floor and not coming up concerns me. Is there anything else I should be looking at?

Tiny
Chphoto1
Jul 22, 2009.
You most likely just need to bleed the hydro-boost system since the brake booster was replaced. After bleeding the hyrdo-boost system, also bleed the brake system as you normally would at each wheel. Follow the steps below to bleed the boost system, let me know how it goes afterwards..


http://www.2carpros.com/forum/automotive_pictures/261618_Noname_708.jpg


Bluelightnin6
Jul 22, 2009.
I tried bleeding the booster and the brake lines (used your instructions and instructions in Chilton manual) and I have the same problem. Did I get a bad booster?

Tiny
Chphoto1
Jul 23, 2009.
That is possible, or you may have accidentally left something loose such as a vacuum line somewhere or something.

Bluelightnin6
Jul 23, 2009.
Took the new boost off and put the old one back on and the pedal is acting normally again. The groaning problem is still there, so it's back to the store for a little exchange action. Thanks again for all your help.

Tiny
Chphoto1
Jul 24, 2009.
I finally got the new booster on and I'm having the same problem. It's still intermittent and the brakes haven't failed or anything, but it still makes the groan, the pedal kicks back there's a thump and the brakes kick in. What's next?

Tiny
Chphoto1
Aug 3, 2009.

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