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73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: fiddler on August 10, 2017, 08:38:30 pm

Title: Normal operation or a lurking problem?
Post by: fiddler on August 10, 2017, 08:38:30 pm

I have a 1974 Chevy C10 step side.  350 automatic with vacuum power assist brakes.  I recently cleaned up all of the old vacuum lines.  The line to the brakes was deteriorated by the carburetor to the point that it was leaking through the walls of the hose.  So it was pulling some vacuum but wasn't right.  Now I have corrected that problem, and I have the truck purring like a cheetah, but when I step on the brakes at idle, I notice the idle speed increases.  Is this normal operation?  Is it impending doom?  Has anybody noticed this before on their truck??  Maybe I need to readjust something?

Thanks for any inputs,

ricky

Title: Re: Normal operation or a lurking problem?
Post by: bd on August 10, 2017, 08:41:52 pm

First, make sure that the power brake booster vacuum hose is 11/32", textile reinforced, stiff-wall EPDM rubber hose that meets SAE J1403 Type L and DOT FMVSS 106 requirements.

Second, replace the power brake vacuum booster.

Title: Re: Normal operation or a lurking problem?
Post by: fiddler on August 10, 2017, 10:58:00 pm

Thanks much.  I will verify the hose with the NAPA guy tomorrow.  The hose I used is a multipurpose from NAPA and is supposed to be suitable for this application but I will verify before I change the out the vacuum booster. 

ricky