Another 3800 series 2 manifold issue

[tracytw]

I am having a manifold issue that sounds similar to other threads I've read about the 3800 series 2 . I have one question that I haven't seen answered yet. Is there or isn't there supposed to be coolant sitting on top of my lower intake manifold when I remove the upper intake manifold?

 

[Enslow]

There should be no coolant sitting on top of the lower intake manifold. It may have gotten there several ways:
1) your EGR passage eroded into the coolant port on the UIM. Replace the UIM with the "surefix" intake manifold from APN and you will never have this problem again.
2) Some coolant may have spilled into the intake as you removed the UIM. This is not likely to happen if you drained the coolant first.

Either way, I'd replace the UIM with the surefix UIM. I'd also change the LIM gaskets from the nylon framed ones to aluminum framed gaskets. Also, when you replace the plastic elbow, use a GM elbow, not Dorman.

 

[tracytw]

how /where does it erode? How would you check to see if that was the issue?

 

[Enslow]

The LIM has a metal tube pointing straight up at the throttle body end. This metal tube goes through a plastic hole in the plastic LIM. If you look at the inside of the plastic hole, you may see evidence of erosion. It may be small and hard to see. Irregardless, this is such a common failure, you should replace the UIM anyway, and also change the nylon LIM gaskets to aluminum.