Pontiac Repair: coolant leak, coolant holes, coolant leaks

Question
95 bonneville 3800, I'm getting coolant in my intake plenum. So with a plate bolted to seal the coolant holes to the trottle body I applied air pressure to the radiator. I thought I would see bubbles at the egr tube, but no. I could hear air, so off came the egr tube to the egr valve and there I have water trying to come up from the bottom of the hole. What appears to be where the machining process took place in drilling the verticle hole in the aluminum. Could the aluminum part be cracked in there? It fills the the plenum in minutes but within 30 seconds of starting the engine, steam is coming from all the exhaust joints.

Answer
Hi KirK:

usually the issue is with the upper plenuim on these cars the plastic warps and the coolant leaks out betwwen the aluminum manifold and the plastic. I have yet to see the actual lower intake manifold go bad but ther is always a first time. You in the right place to look but like I said it's usually the upper plastic piece that is the culprit. If you look around on the net like Ebay ther is a place that sells them and they state that they are not the original equipment part and that the plactic around the egr tube is "beefed" up so eliminate this issue. Good luck :)