Power Brake Conversion Problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**rharris** · 06-16-2018, 11:05 AM

I added power brakes to my 72 c10. I have a new MC for power brake setup, a factory bracket, pushrod, and booster. I have read that the pedal will be somewhat closer to the floor board with the power setup, so that didn't surprise me (only 1 hole in brake pedal). However, the brakes feel harder than manual. They bled up fine, and I bench bled the MC and i do not have a brake warning light. If I step on the brakes while running, the rpm's die off very noticeably. After shutting off the engine, I can hear hissing for a few seconds. Could a faulty booster be the problems? The brakes seem to work the same with the vacuum line pulled off the booster.

**Steeveedee** · 06-16-2018, 12:48 PM

Yup, sounds like a vacuum leak. You should not hear any hissing.

**The Rocknrod** · 06-16-2018, 01:23 PM

Vacuum leak.

**rharris** · 06-16-2018, 08:31 PM

i assume with the engine dying when pushing the brake peddle it would point to the booster. The manifold fitting and vacuum tube are new. I also noticed that when I shift into gear it has a lag time. Guessing that is due to the leaky diaphragm in booster.

**rharris** · 06-22-2018, 05:58 PM

Thanks fellas, new booster came today - works much better. Brakes seem to grab all at once but they work much better. Maybe some adjusting this weekend.

06-16-2018, 11:05 AM	#1
rharris Senior Member Join Date: Apr 2013 Location: Pottsgrove PA Posts: 560	Power Brake Conversion Problem I added power brakes to my 72 c10. I have a new MC for power brake setup, a factory bracket, pushrod, and booster. I have read that the pedal will be somewhat closer to the floor board with the power setup, so that didn't surprise me (only 1 hole in brake pedal). However, the brakes feel harder than manual. They bled up fine, and I bench bled the MC and i do not have a brake warning light. If I step on the brakes while running, the rpm's die off very noticeably. After shutting off the engine, I can hear hissing for a few seconds. Could a faulty booster be the problems? The brakes seem to work the same with the vacuum line pulled off the booster. __________________ 72 Cheyenne Super C10 SWB 2001 Silverado 1500HD Crew 2011 Silverado 2500HD Crew Duramax (Hers) Last edited by rharris; 06-16-2018 at 12:16 PM.

06-16-2018, 12:48 PM	#2
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,081	Re: Power Brake Conversion Problem Yup, sounds like a vacuum leak. You should not hear any hissing. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

06-16-2018, 01:23 PM	#3
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Power Brake Conversion Problem Vacuum leak. __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

06-16-2018, 08:31 PM	#4
rharris Senior Member Join Date: Apr 2013 Location: Pottsgrove PA Posts: 560	Re: Power Brake Conversion Problem i assume with the engine dying when pushing the brake peddle it would point to the booster. The manifold fitting and vacuum tube are new. I also noticed that when I shift into gear it has a lag time. Guessing that is due to the leaky diaphragm in booster. __________________ 72 Cheyenne Super C10 SWB 2001 Silverado 1500HD Crew 2011 Silverado 2500HD Crew Duramax (Hers)

06-22-2018, 05:58 PM	#5
rharris Senior Member Join Date: Apr 2013 Location: Pottsgrove PA Posts: 560	Re: Power Brake Conversion Problem Thanks fellas, new booster came today - works much better. Brakes seem to grab all at once but they work much better. Maybe some adjusting this weekend. __________________ 72 Cheyenne Super C10 SWB 2001 Silverado 1500HD Crew 2011 Silverado 2500HD Crew Duramax (Hers)

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