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Astro air vents fail when accelerating uphill

rpolingrpoling Member Posts: 1
edited April 2014 in Chevrolet
I have a '97 Chevy Astro van, AWD, 80k miles. Recently, while accelerating uphill, the airflow stops coming out of the 4 upper air vents on the dash. This includes Vent and A/C. Air continues to flow from the lower vents as well as the defroster. The airflow returns to normal when I stop accelerating, or go downhill.

A friend told me that it is probably a vacuum leak. My question is.... how do I find and repair this leak?
Any ideas? Thanks!! Rick


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    dpwestlakedpwestlake Member Posts: 207
    Volvo's do the same thing. they have a cut off on the AC. The same will happen if you accelerate hard on a level road. Check your manual.
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    0patience0patience Member Posts: 1,712
    Whether the check valve at the brake booster is not working properly or you have a crack in one of the vacuum hoses is the question.
    One check, start the vehicle, let it run for a bit, then shut it down, wait a couple minutes, and pull the valve at the brake booster. You should hear a decent hiss from it. If you don't. the check valve is bad.

    How does it idle?
    How are the brakes?
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    Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Yep, I'm with Opatience on this one...vacuum leak is closing the upper vents as vacuum drops (under engine load).
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    poisondartfrogpoisondartfrog Member Posts: 102
    Same problem happened recently on my '93 Pontiac Grand Prix. The hard plastic line to the vacuum (reserve) bottle broke. The a/c would switch to the floor during acceleration. It also prevented the fuel purge solenoid from working properly, too. My gas cap would hiss after shutting off the car... unnerving!
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