1984 Chevy Suburban hissing noise- hard braking

1984 CHEVROLET SUBURBAN
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JPPLUMBER
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  • 1 POST
The system holds vacuum as far as I can tell, if I pull the hose off the (power assist unit? the drum thing with the master cylinder bolted to it)with the engine off for a while there is a rushing sound. If I apply the brakes while driving it takes much more effort to stop the vehicle and the little woosh noise it normally makes when braking sounds continually (my 5 yr old says it sounds like a snake) and also the idle is very poor. Is this a power assist problem or a check valve or something else?
Aug 2, 2008 at 10:58 AM
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MERLIN2021
  • ✓ASE Certified Mechanic
  • 17,250 POSTS
  • ASE Certified Mechanic
Shut the truck off, pump the brake until the pedal is hard, hold pressure to the pedal and start the truck, the pedal should sink a bit, if it does, the booster is working, if not the booster needs replacing, or the check valve, to test the valve remove it and try sucking thru both ends, it should work in only one direction. Also, the hose itself should be inspected for cracks.
Mar 15, 2021 at 11:16 AM
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