Brake Vacuum Booster

[dsnyder]

Do these ever leak? I'm chasing down vacuum leaks and I hear a sucking sound that comes from near the firewall and the brake booster. All other hoses have been eliminated as a part of the change to the DFEV carb.

[So Cal Mark]

yes, but usually only when the pedal is depressed

[mbouse]

how about the connection between the vacuum hose and the check valve that goes into the booster... or the rubber gasket at the booster that should be sealing off the check valve?

[BurbankJalopy]

A fun trick to track down a vacuum leak is to carefully and accurately spray starting fluid on the parts you think are leaking. The spray gets sucked into the engine and therefore engine speed increases or decreases. I like to use the 'straw' to get the fluid right where I think the leak may be. Another tip: the leak may not be at the ends of the hoses, it could be somewhere in between and so you may need to spray down the entire length of hose to find the leak. Also, this is good to clean the grease off of the parts as you test them. Have a fire extinguisher handy in case you start a fire. Disclaimer: Before you try this, you understand and assume the risk and the inherent dangers of fire, injury, damage, etc when you use this method.

[So Cal Mark]

you can use something less flammable, like penetrating oil also. I like to use a stethoscope with the probe removed. It's accurate and cleaner