Vacuum hose failure is common due to engine heat and time. Vacuum hoses are made of plastic.Google+
Car Problem Reports
Ford Bronco Failure of plastic vacuum lines
Ford Bronco Problem
Model Year Affected: 1995
Exhaust & Emissions Affected: 5.0L V8
Average Mileage: 161,750 mi (154,000 mi - 169,500 mi)
Visitor, 1995 Ford Bronco, 169,500 mi
All vacuum lines are failing. all plastic lines are britle. starting to replace one by one. haveing trouble finding a good diagram to work off of.
Visitor, 1995 Ford Bronco, 154,000 mi
while changig spark plugs, i had to move plastic vacuum line, and the plastic vacuum line where no longer flexable, they where very rigid and brittle, as a result they broke very easily.