454 330 horse with aftermarket Hardin exhaust. One side needed a new rubber exhaust sleeve due to a small burn hole directly behind the header. I replaced it and within an hour of run time it was back again. Water flow seems good and water wasn't very hot that was dripping from it. Header itself was warm but cool enough to touch. Any idea wtf is happening????

This might be a better question for the general discussion page lot more people go threw that page.

Is the rubber sleeve straight? Even with water flowing, if your rubber hose is bent to compensate for exhaust fittment the hot exhaust air will burn a hole thru the tube.