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#1 |
Registered User
Join Date: May 2012
Location: South Ogden, Utah
Posts: 172
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Idle surge when applying power brakes
I was noticing that when I push on the brake pedal when idling in neutral, the RPM increases about 2-300 rpm. This was during my weekly "start it and run through the gears until it reaches operating temperature".
I haven't yet cleaned off the snow to have a look underhood but I was wondering if this is common or if someone knows what the likely fix is. I'm guessing vacuum leak. Truck is a '71 C20 with power brakes.
__________________
'71 C/20 350/T350. |
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#2 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,216
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Re: Idle surge when applying power brakes
If it does it once it is normal. If it continues while you have your foot on the brake in means a ruptured diaphragm in the power brake unit.
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#3 |
One of the First
![]() Join Date: Jan 2000
Location: St. Augustine,FL.
Posts: 4,054
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Re: Idle surge when applying power brakes
Power brake diaphragm pushes air back into intake runners, which leans Air/Fuel ratio, which caused slight RPM increase.
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DAVID PASSMORE ST AUGUSTINE ,FL ZIP 32084 '71 SWB K/10 CUSTOM DELUXE (Chili) '72 BLAZER K/5 Muscle Truck (Mule) '72 LWB K/20 CHEYENNE (Blackie) |
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#4 |
Registered User
Join Date: May 2012
Location: South Ogden, Utah
Posts: 172
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Thanks to both of you. I'll pay close attention to see if it's momentary or continuous. It'd be bad if the booster is fubar.
If I fly through a stop sign, I'll post up crash pics.
__________________
'71 C/20 350/T350. |
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