Can an intake manifold leak oil in a Chevy Venture van?

Yes, the intake manifold can leak oil in a Chevy Venture van. An intake manifold gasket leak is a common problem with these years due to the material the OEM manifold gaskets were constructed with which was plastic (nylon to be exact). This plastic degrades and leaks after exposure to oil and heat under the hood. Replacing an intake manifold gasket in vehicles with the 3400 engine takes between 6 to 8 hours of labor according to most labor guides depending on whether or not the fuel injector rail is serviced while the plenum cover and upper intake is off the vehicle.