Maybe that could help. You obviously know more than I. Interesting that you say that about the pump. I had replaced my waterpump with an aftermarket before the headgasket repair and was wondering if that may have caused my overheating problem with the other engine. My hoses always looked ready to "explode" from pressure. I wasn't sure if it was because they were after market hoses or because the pump wasn't able to "keep up". With the replacement engine, the waterpump attached looked original and had no play in the bearing. The hoses also looked great so I decided to have them leave it on and give me the other pump as a back up. Anyone know if aftermarket pumps could "underperform" in this area and cause problems?