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Newer GM power brake boost systems utilized a combination of hydralic and vacuum boost on the brakes. The hydralic boost comes off of the power steering pump.
If the pump isn't turning fast enough you won't get any boost. This will happen if the belt slips. It will be particularly noticable at slow engine speeds.
The boost also won't work very well at slow speeds if the fluid level is down.
Since your problem isn't exclusive to the power brakes I wouldn't worry about the vacuum pump. If the vacuum pump were bad the power brakes would have a problem but the power steering would not.
Start with the easy stuff--check the fluid level and the belt tension.
If you have a serpentine belt and you have no idea how old the belt is or it has been a long time since the belt was changed, change the belt. An old belt may look okay but it may have stretched out over time to the point the automatic tensioner can't tension the belt tight enough any longer.
Good luck and happy trails.
Mark O. |
RV and bus conversion info since 1996.
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