IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Auto Tech => Topic started by: just plain john on August 24 2011, 05:32:48 PM
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What triggers the brake warning light, low line pressure? If the fluid is full, would that point to the master cylinder? The brakes seem fine, but the light comes on, sometimes bright, sometimes hard to see.
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Is this a powermaster, vacuum or hybroboost system?
The brakes seem fine, but the light comes on, sometimes bright, sometimes hard to see.
So - sometimes it illuminates but very dim? THat sounds like an electrical issue, possibly a weak/loose ground.
Here's the circuit diagram for the PM:
http://www.gnttype.org/techarea/images/PwrMstr.gif (http://www.gnttype.org/techarea/images/PwrMstr.gif)
Looking at this, the light can be triggered by three things - The combination valve (on frame rail under brake assy), the parking brake switch, or the brake pressure switch on top of the PM.
Master cylinder failure is usually indicated by a soft pedal that will press down more the longer you keep your foot on the pedal.
Assuming this is a Powermaster system - do you notice the brake pressure motor running more than normal?
Powermaster diagnosis:
http://www.gnttype.org/techarea/brakes/PwrMstr.html (http://www.gnttype.org/techarea/brakes/PwrMstr.html)
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I'm sorry, I guess I should have been more specific. This is not a TR, nor the Powermaster brake system. Just a plain disc/drum vacuum setup on a mid 80's Chevy truck. Pedal seems fine, and does not creep down if depressed.
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Do the brakes still work as they should? Just he light is coming on?
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