Is it coolant or oil leaking at the back? Which brand and type gaskets did you use?
GM calls for a dab of RTV on the cylinder head side of the gasket...
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...and a little less than 1/4-inch wide RTV on the China walls extending 1/2-inch onto the gaskets.
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GM calls for threadlock GM P/N 12345382 on the eight intake manifold bolts. I forget what I used, but Permatex and others usually have a cross-reference table for comparable products. I don’t think that any of the bolts extend into a water passage, but a few do end up in the open lifter valley.
What broke- the quick connect or the fixed line in the intake? Not sure how you would fix the line, but a new GM intake can be had for around $400. I had to go that route since mine was cracked at the ECT sensor port, I will say that working with a brand spanking new and clean intake was pretty nice.
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