: Oil in intake manifold (eek!?)



eldorado1
03-18-04, 09:00 PM
I removed the top cover on my 1994 Northstar, and noticed lots and lots of oil in the intake manifold, puddles too! I don't think it's coming from the PCV since the throttle body is clean... What's going on? :suspense:

BeelzeBob
03-19-04, 12:24 PM
I removed the top cover on my 1994 Northstar, and noticed lots and lots of oil in the intake manifold, puddles too! I don't think it's coming from the PCV since the throttle body is clean... What's going on? :suspense:


What's going on...???? Nothing. Perfectly normal.

Any intake manifold will get some oily residue in it over time. If you are used to conventional style intakes with carburetors or throttle body injection the gasoline sluicing thru the "wet" intake keeps it pretty clean. Also, most conventional V8 manifolds have a rather high floor so the ports are all "down hill" and any deposits run to the cylinder head ports.

The Northstar intake on a 93/94 is just the opposite. It is a "dry" intake....no fuel going thru the intake to clean it out. All the fuel is put in at the port at the injectors so the intake just handles air and the PCV gases.

The Northstar intake also has a significant "sump" in it that is low...well below the level of the intake runners. So any buildup over time just lies there.

What you are seeing is not likely oil....just the heavy ends of the hydrocarbons going thru the engine. Heavy ends do not vaporize easily. All the fuel has some small amount of "heavy ends" in it that do not vaporize and lie in the manifold. In addition, the fuel that reaches the crankcase on a cold start (several ounces each start) is heated in the oil as it comes up to temp and is pulled into the PCV as vapor. That fuel has heavy ends in it that condense in the intake manifold and then just lie there. There is also some small amount of oil mist pulled over in the PCV that is perfectly normal.

What you see there has accumulated over tens of thousands of miles. It is absolutely nothing to worry about. Any engine with a sump style manifold/dry PFI manifold will do that.

eldorado1
03-19-04, 12:38 PM
fweew... good to hear. So... how should I get it out? maybe soak most if it up with clean rags, put it back together, and run some top engine cleaner through it?

BeelzeBob
03-19-04, 01:10 PM
fweew... good to hear. So... how should I get it out? maybe soak most if it up with clean rags, put it back together, and run some top engine cleaner through it?

Did you miss the part about it being perfectly normal to be there...???

Leave it alone. Forget about it. No need to clean it out. It will just return. It is not hurting a thing so you are wasting time and money cleaning it out.

Why run top engine cleaner thru it..?? Leave it alone.

eldorado1
03-19-04, 02:23 PM
Did you miss the part about it being perfectly normal to be there...???

Leave it alone. Forget about it. No need to clean it out. It will just return. It is not hurting a thing so you are wasting time and money cleaning it out.

Why run top engine cleaner thru it..?? Leave it alone.
but..but...but... a clean engine is a happy engine! :)

BeelzeBob
03-19-04, 02:49 PM
but..but...but... a clean engine is a happy engine! :)

Not in respect to the inside of the Northstar intake manifold. It "likes" to get "oily"....just clean it out and check back later...it will be all oily again.