The thermostat is not opening fully creating a great amount of suction, which in turn speeds up the flow of coolant by 2-3 times normal. This in turn creates a venturi effect( Bernellis Theory ), and cause things to contract within .
But I also failed science........
Just a guess, but maybe one of the techs showed rubberstamp this with there approval, or toss it into the scrapheap of suggestions.
98 300 DT