I have a 95 Blazer, Vortec V-6 (W), and am in the process of replacing the intake manifold gaskets due to a leak. I have the upper plenum off, and manifold off and want to flush the coolant passages in the block. I removed the block drain from the driver's side and flushed both the front and rear passages and they drained thru the block drain. I added water to the center passage and noticed it wasn't draining to the block drain or anywhere else. Where does the center passage drain to? Thanks.

John

 

The center port is a heat riser port (throw back from earlier engines) and is not associated with the cooling system.

 

Thanks for the info. I assume the same port (center) on the passenger side of the engine is the same same thing - a heat riser port. The passenger side center port is almost completely plugged with carbon.

John

 

Yep. Same thing. The heads are identical side to side.