Thread: Upper Plenum

I think you should get a couple 1/4" NPT pipe plugs, plug the coolant ports going into the UIM and never worry about your UIM again.

Make it bulletproof and do the LIM's at the same time. Best way to go IMO.

wouldnt that make my plenum a little hotter and cause it to warp? I dont wanna sound like an amateur but what is IMO cause ive seen it here a few times? lol sorry for my lack of knowledge on some stuff.

No worries, we were all new at one point.

IMO = In My Opinion

Plugging the holes only does one thing. It keeps the coolant from flowing into the plenum and past the EGR tube where the heat cycle cracks happen and flood the UIM/LIM then hydrolock the engine and bigger issues.

The purpose of the coolant in the TB is supposedly to keep from icing, I'm unsure if that's what GM had in mind, but it's minor. Many many people have blocked these ports w/o problems. I did on a car that lives in Erie PA on the edge of the lakes. No problems at all. Owner is very happy that his car can never die from the upper rupturing. The temp of the upper won't change as there isn't enough coolant going through it to affect temp.

dont block the coolant ports unless you open up the side port on the lower intake manifold to compensate for the flow. the coolant that flows through the upper intake manifold and throttle body is part of the flow to the rear head.

Crap...did I leave that out?

LOL, I did one last night. You'd think it was fresh in my noggin.