Brake issue on 99 yukon

[elt]

So my brake pedal is acting weird! When i push on it there is an air leaking sound coming from pedal area. Very hard to push pedal in. I still have brakes but requires a large amount of pressure to do it.
Is my master cylinder going out?

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[mtl111]

Sounds like your vacuum booster, classic symptoms....hissing sound and hard pedal.

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[iamdub]

+1 vote for failed vacuum booster.

 

[willxfs]

Yep. I vote vacuum booster. Mine went out a couple of months ago on my 1998 rig. Same symptoms as you. Plus the truck would almost stall out while at a stop light with foot on brake due to the big vacuum leak.

 

[elt]

Mine is doing that too. Thank you guys.

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