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Brake Booster?

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Old Aug 24, 2015 | 06:29 PM
  #1  
lmayer460's Avatar
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Brake Booster?

1978 F-150 Custom 4x4

Thinkin I have a problem with the brake booster, here are the symptoms:

When driving the brakes work fine on the first pump, but when released and pumped the second time they are stiff and about 50% braking power. This condition persists if i continue to pump the brakes, but if I continue driving without braking they return to normal in a short period of time and It will feel fine again only on the first pump...almost like its taking several minutes for the vacuum to build up in the booster.

No recent work on the brake system has been done and the fluid level looks good. I'm going to inspect the check valve and the vacuum line tonight after work....any other thoughts?
 
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Old Aug 24, 2015 | 06:49 PM
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That sounds more like a restriction in the vacuum line than a problem with the booster. Make sure the line isn't collapsing or hasn't deteriorated inside.
 
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Old Aug 24, 2015 | 08:10 PM
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I think you are on the right track checking the line and valve. My OE check valve cracked and leaked. Replacements are usually in stock in the "Help" section at the AP store.
 
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