So when i switched intakes for the 4 barrel conversion, i hooked up the brake booster to the vacuum port at the base of the carb... i no longer had assisted brakes. I mentioned it i another thread and the general concensus was to move the vacuum to the intake. I did that yesterday and took it out for a spin today... still no power brakes. I havent heard a leak, and did a pretty good job of sealing everything properly. Someone told me to bleed my brakes, and i probably will, but i dont think that will have anything to do with loosing my booster after an intake swap... Any thoughts? Thanks, Northern
With the engine running, at ide,if you disconnect the brake booster vacuum hose. Does it have any vacuum?
'Seems strange that you'd lose the power brakes right after swapping a carb & intake. There are basically 3 possibilities: 1. The booster is not getting vacuum (does the hose fitting suck air and idle get rough when disconnected?) 2. The vacuum booster is bad 3. the check valve on the booster is bad. Bleeding the brakes has nothing to do with it.
Since changing the intake and carb, did it ever backfire? If so, do as Larry states and take a look at the check valve on the brake booster.
I was sweating that Jason...because it might have back fired a few times... I got vacuum back, and I'm not exactly sure why. I cranked the car, then pulled the hise off the booster, nothing. Put my thumb over the hose, nothing. Obviously the vacuum port on the intake isn't pulling. Pulled the plug off the carb base, sucked hard then instantly died. Because of the geometry, I had to turn the hose around, then plugged the booster in to the carb, plug the intake, cranked fine...and booster worked. Pulled the plug on the intake, engine died. Wth. Moved the booster back to the intake, plugged the carb, everything works. :/ The only thing that makes sense right now is the vacuume hose has a valve in it and only flows one way (maybe a safety from back fires?) Thanks for the advise and directions to start poking around, Northern
'Sounds as if there was some sort of blockage on the vacuum port or connector, although I can't imagine what.
That is what the small plastic check valve on the brake booster should do. It allows the engine to pull vacuum from the booster but not allow it to pressurize from something like a backfire. Glad to hear it is working for you now.
I don't have one of those... I just have a metal nipple sticking out of the booster with a 90* turn. Its got to be in the hose. Interesting. Learn something new every day.
The check valve is there to maintain vacuum in the booster with the engine off. It should hold enough for a couple applications of the brakes, it's a safety backup in the event the engine dies and you need to stop.
