1996 GMC Jimmy Maybe Mastercylinder

1996 GMC JIMMY
138,043 MILES • 6 CYL • 4WD • AUTOMATIC
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JOEAUTO
  • MEMBER
  • 1 POST
The trouble is with the brake system. When depressing the brake pedal it sounds like there is air coming from under the dashboard. Also when depressing the brake pedal it feels very hard to move and as the problem continued the engine would sometimes quit when I have traveled for a while. At this time it is unsafe to operate.
Jul 27, 2009 at 8:00 AM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Sounds like the brake booster is leaking

To check the vacuum 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.
Jul 27, 2009 at 8:06 AM
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