Rushing air sound when I press brake pedal

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  #1  
Old 11-08-18, 11:14 AM
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Rushing air sound when I press brake pedal

I still drive my trusty old 92' Ford Ranger XLT with 2.9 V6. When I press the brake pedal, I hear hissing or rushing air from behind dashboard/firewall. The brakes work. But the pedal seems to ride a little higher and harder.


I also had someone listen for that sound in the engine compartment when I pressed brake pedal. The other person heard the rushing air sound in the area of booster/master cylinder..................failing brake booster then?
 
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Old 11-08-18, 12:40 PM
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Booster is leaking vacuum!
 
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Old 11-08-18, 12:44 PM
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I also vote that the master cylinder booster is leaking.
 
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Old 11-08-18, 01:00 PM
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Ok. The parts store has to order one from their warehouse.

I looked at a picture of the part. I assume the rod that goes through the firewall connects to the brake pedal linkage?

Do these power brake boosters come with the check valve?
 
  #5  
Old 11-08-18, 01:02 PM
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It's probably the "plunger" that is leaking vacuum under the dash on the inside of the passenger compartment. and you "may" be able to improve the seal with some dielectric grease . . . . or at least extend the life of the booster.

After 26 years, that puppy may have dried out, and might benefit from being lubricated (to improve the seal of the plunger).
 
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Old 11-08-18, 01:09 PM
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The brake booster was replaced 4-5 years ago. All they have for my make/model is remanufactured. I also noticed brake fluid residue where the MC attaches to the booster
 
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Old 11-08-18, 03:21 PM
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Brake Fluid isn't usually routed through the Brake Booster, so if you have a leak near, or in, the Master Cylinder, that does't implicate the Brake Booster. Many times, Master Cylinders have internal leaks that don't produce external leaks like you're witnessing.

But since you have this "hissing noise" accompanying the use of the Brake Pedal, I would ask if you also have a "sinking pedal" when pressure is applied to the Brakes for an extended period of time (longer than a Stop Light) ? Do you hear the "hiss" when the engine IS NOT RUNNING and retain a firm pedal ?

You might have both issues . . . . a Master Cylinder leaking Brake Fluid AND a vacuum leak associated with the Brake Booster's Plunger.
 
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Old 11-08-18, 05:03 PM
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lso noticed brake fluid residue where the MC attaches to the booster
Sounds like you may have a bad master cylinder that is leaking fluid into the booster causing it to fail!
 
  #9  
Old 11-08-18, 07:28 PM
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I don't have the sinking pedal yet. And I don't hear the rushing air sound when I depress the brake pedal with the engine off.
 
  #10  
Old 11-10-18, 04:19 PM
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I replaced the power brake booster myself today. Braking function is good. Done.
 
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