I see white smoke inside the plenum a few minutes after start up basically when normal engine operation. Car has a bit of rough idle (1988 camaro 305 tpi). My coworker is telling me I have coolant leak through the intake manifold, is this true? If so, does that mean my intake manifold has a Crack throughout the coolant passage or is it a bad intake manifold gasket? I can see the smoke through the throttle body blades with engine off, of course.

 

The coolant passes through the front of the manifold and in the rear there are block off plates in the intake manifold so no coolant flows through the rear. IIRC both of those passages and block offs are spaced out from the intake (air in) ports. I don't think coolant can enter the intake if the gasket is bad. The front air port (manifold runner) is separated from the front coolant passage by an aluminum wall so if you have a crack it would be in that manifold port. Can you smell the smoke? coolant, oil and exhaust will have a different smell, maybe you can narrow down what it is from the smell. Your EGR system also goes into the plenum so I would check that as it may be letting gasses or smoke into the plenum after you shut the engine off. Your PCV valve also is piped into the intake ports of your manifold. If you have any internal engine smoke it will bleed into the intake manifold and may rise into the plenum. The old Dodge hemi's smoked all the time from the valve cover breathers after the engine is turned off.

 

Thanks, it was smoke coming from the pcv valve. Not alot of smoke but it did smell a bit like oil. By the way, not sure if you know the answer to this but I get a suction/vacuum from the ccv on passenger side valve cover is that normal?

 

That is normal. That is where the engine crankcase takes the clean air in and the PCV valve lets it out. The crankcase becomes a vacuum from the rotating mass.