Brake problem? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

71400lb · 01-07-2005, 12:33 AM

I have a 71 C/20 Long bed 2 wheel drive. The previous owner installed a Crane Cams back-up canister booster for the breaks...told me in case the main brakes fail, the back-up system will get you home.

Right now when I press the brake pedal as hard as I can to stop, the truck slows down quickly but the tires don't lock up.

My question is, shouldn't my breaks lock up the tires when I floor the brake pedal?

Is it normal the way the truck stops or do you think there's a problem?

Also could it be that the main brakes are not working and I'm only stopping with the Crane Cams back-up canister?

Thanks all,
Rick

1971 Cheyenne 3/4 Ton Long Bed
400/400
3.73/open H052 10-bolt

rodnok1 · 01-07-2005, 11:01 AM

The Vacuum canister stores engine vacuum for use with power brakes, it is NOT a back up brake system. They are for engines that don't produce enough vacuum normally for power brakes. Do you have disc/drum or drum/drum? If you have disc/drum and the back brakes are way out of adjustment they won't lock up. If you have drum/drum, they all could need adjustment. I like to have the rears just locking up when truck is empty, so when loaded it stops better. Your brakes could also be worn out, I would check the shoes and adjustments and see if it helps. I have driven a couple truck that the brakes wouldn't lock up except on ice and they stopped excellent.

Rods&RidesLeon · 01-12-2005, 08:14 AM

Your brake booster should have a check valve in the vacuum inlet, This valve will allow your booster to hold vacuum even if you unplug it. A typical canister don`t have the volume that it takes to bring the booster to 16-18 psi, If your shoes and/or pads are OK and adjusted, and they still don`t work. Check the vacuum pressure of the motor, If they just put in the new cam, The valves may not be adjusted right or the timing may be off.
You really shouldn`t need a canister.
Another thing to check is, Make sure your booster is good, After shutting off the motor, wait about 15 seconds and then pull off the vacuum line to the booster and see if it still holding pressure.

01-07-2005, 12:33 AM	#1
71400lb 71400lb Join Date: Jun 2004 Location: Charlotte NC Posts: 74	Brake problem? I have a 71 C/20 Long bed 2 wheel drive. The previous owner installed a Crane Cams back-up canister booster for the breaks...told me in case the main brakes fail, the back-up system will get you home. Right now when I press the brake pedal as hard as I can to stop, the truck slows down quickly but the tires don't lock up. My question is, shouldn't my breaks lock up the tires when I floor the brake pedal? Is it normal the way the truck stops or do you think there's a problem? Also could it be that the main brakes are not working and I'm only stopping with the Crane Cams back-up canister? Thanks all, Rick 1971 Cheyenne 3/4 Ton Long Bed 400/400 3.73/open H052 10-bolt

01-07-2005, 11:01 AM	#2
rodnok1 Registered User Join Date: Jun 2003 Location: Linden, North Carolina Posts: 617	The Vacuum canister stores engine vacuum for use with power brakes, it is NOT a back up brake system. They are for engines that don't produce enough vacuum normally for power brakes. Do you have disc/drum or drum/drum? If you have disc/drum and the back brakes are way out of adjustment they won't lock up. If you have drum/drum, they all could need adjustment. I like to have the rears just locking up when truck is empty, so when loaded it stops better. Your brakes could also be worn out, I would check the shoes and adjustments and see if it helps. I have driven a couple truck that the brakes wouldn't lock up except on ice and they stopped excellent. __________________ 64 Panel Rebuild Pics Clutch Replacement and Borg Warner T10 Trans Rebuild 64 Panel 1/2 Ton 350cubes/400hp BorgWarner t-10 3:73 Auburn Posi

01-12-2005, 08:14 AM	#3
Rods&RidesLeon Registered User Join Date: Aug 2004 Location: Crosy TX Posts: 46	Your brake booster should have a check valve in the vacuum inlet, This valve will allow your booster to hold vacuum even if you unplug it. A typical canister don`t have the volume that it takes to bring the booster to 16-18 psi, If your shoes and/or pads are OK and adjusted, and they still don`t work. Check the vacuum pressure of the motor, If they just put in the new cam, The valves may not be adjusted right or the timing may be off. You really shouldn`t need a canister. Another thing to check is, Make sure your booster is good, After shutting off the motor, wait about 15 seconds and then pull off the vacuum line to the booster and see if it still holding pressure.



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