GMC Repair: intake manifold, upper intake manifold, manifold gaskets

Question
I removed the intake manifold from my 2000 5 litre Savanah van with 72k miles, to change the intake manifold gaskets. When I separated the top manifold from the bottom one, I found the inside of the top manifold coated with oily grit. I also noticed that the injectors don't make a tight seal in the manifold. Is this condition normal, or if it's not, what could be the cause of the grit? I've regularly changed the air filter.

From what I read on the internet, Dexcool was the likely cause for the manifold gasket failure. I'm going to flush it good, and install Prestone antifreeze.

Thanks

Answer
Hi,Michael

The injector seating and oily grit is normal,this is due to engine blowby,the injectors fit slightly loose in the bore because they use a bushing type of seal and since they are located internal to the manifold there is no need for a tighter seal,clean the upper intake manifold and install a new PCV valve,this will keep down the oily grit.
The intake manifold seals failed because,the seals that were installed by the factory were of a design that lead to overtorquing of the lower intake,over time and heat exposure they would fail,GM issued updated gaskets/seals to correct this and set new torque specs to keep the seals/gaskets from failing,Dexcool coolant was not the cause of the failed gaskets/seals.


ED