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

69sixpackbee · 03-23-2005, 06:17 PM

Heres the scoop:
My '72 has new calipers, rear cylinders, pads...you know, all the stuff. I have a brand new booster an a good master. This problem I am going to describe happened before I swapped the booster out as well. When the engine is cold and fast idling and the truck has been setting for a while, the brakes are nice and "touchy" as in barely any pedal effort to send you through the windshield. After I go a few blocks the brakes need alot more effort to stop. Even when going slow. The engine has 18-20" vacuum when idling warm and has no leaks in the power brake booster because the idle is nice and smoothe all through the pedal travel. This acts like a poor vacuum condition yet the engine has plenty. It is a stock 402. The connection to the vacuum booster is tapped off of the manifold runner behind the carb. This is a Performer dual-plane intake. Should I attach the hose to the carb base instead or what does this sound like?
Thanx!
Bud

farside847 · 03-23-2005, 06:25 PM

By chance does it happen when the roads are wet? My brakes grab harder
when it rains and it burns off after a few minutes.

69sixpackbee · 03-23-2005, 06:30 PM

Nope. No diff.

**pjmoreland** · 03-23-2005, 07:08 PM

I had a problem with my brakes a while ago where the little threaded rod that comes out of the booster and pushes the master cylinder was threaded out too far and wasn't allowing the master cylinder to return all the way back when I wasn't pressing on the brakes. This made it so that the brake shoes weren't allowed to release all the way from the drums when I released the brake pedal. Not sure if this is the same problem you are having.

tom hand · 03-23-2005, 08:42 PM

I would check pjmorelands sugguestion....I have had this problem and though the simptoms were not exactly as you discibed it gave me fits till I figured it out....make sure the pedal still has some freeplay when it is warmed up

69sixpackbee · 03-23-2005, 08:47 PM

I'll check that!

03-23-2005, 06:17 PM	#1
69sixpackbee Registered User Join Date: Jan 2001 Location: Sabinal, Texas Posts: 1,706	Power Brake Problem Heres the scoop: My '72 has new calipers, rear cylinders, pads...you know, all the stuff. I have a brand new booster an a good master. This problem I am going to describe happened before I swapped the booster out as well. When the engine is cold and fast idling and the truck has been setting for a while, the brakes are nice and "touchy" as in barely any pedal effort to send you through the windshield. After I go a few blocks the brakes need alot more effort to stop. Even when going slow. The engine has 18-20" vacuum when idling warm and has no leaks in the power brake booster because the idle is nice and smoothe all through the pedal travel. This acts like a poor vacuum condition yet the engine has plenty. It is a stock 402. The connection to the vacuum booster is tapped off of the manifold runner behind the carb. This is a Performer dual-plane intake. Should I attach the hose to the carb base instead or what does this sound like? Thanx! Bud

03-23-2005, 06:25 PM	#2
farside847 Registered User Join Date: Feb 2005 Location: Bay Area, California Posts: 995	By chance does it happen when the roads are wet? My brakes grab harder when it rains and it burns off after a few minutes. __________________ 1971 Chevy C10 Shortbed Stepside, 307v8 3-on-the-tree

03-23-2005, 08:42 PM	#5
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	I would check pjmorelands sugguestion....I have had this problem and though the simptoms were not exactly as you discibed it gave me fits till I figured it out....make sure the pedal still has some freeplay when it is warmed up __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

03-23-2005, 06:30 PM	#3
69sixpackbee Registered User Join Date: Jan 2001 Location: Sabinal, Texas Posts: 1,706	Nope. No diff.

03-23-2005, 07:08 PM	#4
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,466	I had a problem with my brakes a while ago where the little threaded rod that comes out of the booster and pushes the master cylinder was threaded out too far and wasn't allowing the master cylinder to return all the way back when I wasn't pressing on the brakes. This made it so that the brake shoes weren't allowed to release all the way from the drums when I released the brake pedal. Not sure if this is the same problem you are having.

03-23-2005, 08:47 PM	#6
69sixpackbee Registered User Join Date: Jan 2001 Location: Sabinal, Texas Posts: 1,706	I'll check that!



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