Are my brakes working?????

[71400lb]

Here's the situation...previous owner installed a Crane Cams Canister back-up booster for the brakes. He told me that if ever the main brakes fail, the back-up would get you home until you fixed the main brakes.

Lately, unless I'm just used to my other car, when I stomp on the truck's brakes, it slows down quicly, but the wheels certainly don't lock up. I stomp on the brakes as hard as I can and the wheels never lock up!

My question is this; does this sound normal for these trucks to have brakes that don't lock up? Or is it possible that the main brakes aren't working and I'm only using the Crane Cams back-up system when I hit the brakes? If I hit the brakes that hard on my 67 Chrysler 300 you'd be thrown through the windshield!

I believe they are power brakes, since it has a big booster can behind the dual master cylinder resevoirs.

Thanks,

Rick
1971 Cheyenne C/20 Long Bed 2 whl drv
400/400 Turbo
3.73/Open

[JimKshortstep4x4]

Sounds like something is not right. Have you tried stopping on gravel to see if all four wheels will lock up?

Also, do you have enough vacuum and is your booster a double diaphragm style?

Jim

[spencra]

Definately something wrong. Anti locking brakes are a long ways away from these models. On the power braking trucks the pedal is just easier to push on to get the truck to brake as opposed to manual brakes, which is like the equivalent of doing a leg press, just to get it to stop.

[jhow66]

The way I read your post is that you do not have a back-up brake system but a back-up vacumn system. If this is the case your engine must have a "wild" cam that does not pull enough vacumn to operate the power brakes. This is why your brakes seem hard to push.Only way to cure this is go to manuel brakes or change cams or add a electric vacumn pump.

[71400lb]

Thanks all for the responses.

Jhow66, I think you're on to something. YES, it's a back-up vacuum canister about the size of a 32 oz Helmann's Mayonaise jar. And the previous owner told me he DID in fact change the cam. He added a "towing cam" from Comp Cams. He said it smoothed out the idle alot. He used the truck for towing sometimes.

So am I to deduct that the guy probably DIDN'T install the canister as a "back-up" in case the main brakes went, but he installed it because the new cam created less vacuum so he needed to add a vacuum canister(as a booster) just to get the brakes working again?

If I add an electric vacuum pump, is that a big install or is it cheap and easy?

Thanks again,

Rick
1971 Cheyenne C/20 Long Bed 2 whl drv
400/400 Turbo
3.73/Open

[JimKshortstep4x4]

I would suggest checking out your booster and vacuum before adding a vacuum pump. Usually an engine with a smooth idle has adequate vacuum.

Have you taken a vacuum reading, yet?

Jim

[Longhorn Man]

yeah, an RV cam shouldn't have any vacume problems. you shouldn't need an extra vac can untill you need a high stall converter to idle in gear.

[jhow66]

How smooth does it idle? (how much vacuum does it pull at idle?)
Never heard of "back-up" brakes. Yes
pump-don't know as I have never priced one-should be easy to install.
Here is how to check to see if your booster is working--step on brake and hold with engine off--start engine--if your booster is working the brake petal will fall some when engine starts.

[rustyold72]

Does it hiss when you apply the brakes?
Had the same problem on my friends 76 C10, ended up changing the booster, master cyl, and both front calipers, after that it would toss you thru the windshield if you stomped on the brakes
BTW Electric vac pump is easy, available on several GM/Ford cars/trucks, hook up 12v, mount it, hook it to the booster, and it works, available in either parts stores or junkyards, but from the sound of it you don't need it, if it idles smooth you're generating sufficient vacumn to run power brakes

[71400lb]

No hiss when I apply the brakes. The idle is "smooth" as in not lumpy. This is a 400 small block Chevy motor out of a 1972 Nova, bored .30 over and I don't know the number of the cam. But I do remembe rthe guy said he set up the truck specifically for towing, i.e. tranny cooler, electric brakes for trailer hookup, 3.73 gears, and this "towing cam". Best I can describe the idle is that it's similar (in smoothness) to my 1998 Mustang GT stock idle.

Thanks for the tip, I will definitely try the "stomp on brake with engine off/then on" trick to see if the booster is to blame.

I don't have a vacuum guage so I don't know what vacuum it's pulling at this time.

I guess I misunderstood what this Crane Cams Brake canister does...I mistakenly called it a "back-up" brake system, but it's actually a "reserve" vacuum unit.

Rick

[ChevLoRay]

I had a '64 Bonneville, and the hydrovac (brake booster) diaphragm began leaking. When it was leaking, I heard a hiss when I hit the brakes and the idle got rougher when on the brakes.

I have an RV cam in my truck and no problems at all with my brakes. It has been converted to discs on the front, but before the conversion, the right rear brake would lock on a hard stop. Since the conversion (new booster, M/C and proportioning valve), and the break-in, the have not locked up (knock on wood). I still need to rebuild the rear brakes, but haven't reached the "do or die" point.