What psi of Vacuum should come from the mainfold? I lost my power brakes and vacuum at idle is about 14.5 psi. I changed all my vacuum hoses so no leaks at either end of the vacuum hoses. To further check for leaks I sprayed carb cleaner all around; vacuum lines, manifold & carb base. Slight vacuum psi increase when I spray the base of the carb - only about 1 psi to 15.5 psi. Car has 66K orig miles so can't be a flat cam. Pops rebuilt engine in the '80's at about 50K due to a spun rod bearing. Other than that what should I look for?
You need to plug off the booster and check again. It sounds like the Booster sprang a leak. With everything properly tuned and running right, your engine should pull 18-22" of vacuum. BUT, if isolating the booster doesn't bring up the vacuum, you'll need to diagnose the engine mechanicals (regardless of whether the engine has 6K or 66K, you can have a mechanical problem that drops vacuum)
Thanks for the tip Silvertwinkiehobo - I didn't think about isolating the booster out of the picture. I'll check that out tomorrow - I'd rather it be something as easy as the booster than some engine mechanical dropping the vacuum.
Silvertwinkehobo, You were right, my booster does have a leak. My measurements today @ idle. Direct from the manifold I'm getting between 14-15" of vacuum. When I plugged off the boosters vacuum hose vacuum increased to 17-17.5". Spraying some carb cleaner around the base of the carb, vacuum increased 18-18.5" You stated 18-20" so I guess when I fix those two issues I'll be at the lower end at 18.5". I've read that sourcing boosters from Rock Auto is hit or miss whether you get a good one or not? Any other suggestions? Steven
Actually, a lot of the guys over at FullsizeBronco.com swear by RockAuto and swear at O'Really's and Vatozone. This is by no means an endorsement of RockAuto, but I think you have a good chance of getting what you need.
