I recently made a post about VC-9 and how well it cleaned the entire system. The nearly new Oil Cooler is working much better after flushing 9 times before the water was clear. One problem that didn't go away is the ECT has a sort of wave effect ( 198, 199, 200, 201, 202 etc on up to 215) or more and come back down own its own. Sometimes hitting the 220 mark causing the fan to run. This condition occurs under constant load (15lbs boost), steady speed (65 mph), roughly 2400 rpm (4.88 Dana S110). I must also note that the truck is slightly modified. No Cat, No Muffler, Welded up EGR Cooler. Also my empty weight truck and trailer is 18,900 lbs. The load I took to Winnie, TX this morning weighed roughly 11,000 lbs. GVCW 29,900lbs.
When I returned home, I measured the water flow for 5 minutes using a spare 3/8" hose hooked to the EGR return to reservoir tank.
Work Truck - 5:00 min - 2.0 quarts coolant / Personal Truck - 5:00min - 3.5 quarts coolant.
I'm sure I'm answering my own question, but it looks like I need a water pump.
Does anyone know the proper way to test the water pump? I've looked for a tutorial or how to change the pump on powerstroke.org and cant find anything. Maybe someone has a link or some first hand knowledge and willing to share. Or do you just dive in the fan clutch with a 2X4 a pipe wrench and cheater bar?