Well Katrinka is once again back in operation at a cost of $275 for a recored radiator, $115 for a water pump and gasket and $25 for a suction fan. We did remove the hood and lower hood support to gain access to the hardware and hose clamps. Hood removal is pretty straightforward, loosening the setscrew in the middle of the hinge rod, then driving the rod out with a long drift pin. Then lift the hood off and set it aside. Then remove the bolts that hold the lower hood support and pull upward and forward, clearing the hydraulic cooler lines.
We believe we have found the reason for the failure. Altho the new fan blades are three quarters of an inch away from the radiator core, the tip passes the shroud at the 6 o'clock positon, clearing the shroud by a less than a quarter of an inch! That's right, the tips of the fan actually travel BELOW the radiator core! The tip of a blade is almost an inch below the edge of the bottom tank's seam with the core.
I put the water pump in a vice and used a dial indicator to measure the movement of the tip of a blade as I forced the water pump impeller back and forth, the shaft moving in the worn bearings. The max movement of the top of thee blade was .080 inches. That would mean that in a static condition the blade would be around an eighth of an inch from the shroud. Dynamic conditions are different since the fan is sucking air through the radiator and as Newton's law says, "for every action there is an equal and opposite reaction" meaning that the flexible nylon fan is pulled towards the radiator!
We discovered another factor. The bottom of the radiator is mounted to the frame using rubber donuts thru which passes a 14 mm head bolt. When examined carefully the mounts were locating the radiator as close as possible to the fan as it could be. Loosening the bolts allowed the radiator to be placed another 1/8 inch from the fan.
The bottom line is the failed bearings in the water pump allowed an already close fan blade to touch the shroud when combined with all the other factors mentioned. The final failure occured when the fan blade actully hit the edge of the shroud, deflecting it towaards the radiator. Once on the wrong side of the shroud the blade was bent inwards toward the radiator and ultimately wiping out 6 core tubes where they enter the lower tank.
Since Katrinka is such a beautiful machine with only 800 or so hours on her I decided to go for a recore rather than a repair to the old core by soldering off the core tubes and filling in the holes left in the lower tank. I also went for an OEM pump rather than an aftermarket pump which would have been around 30 dollars less.
Warning!! Loosen your fan belt and check for play or slop in the water pump shaft!! Remember there was no noise and no leakage, just sideways movement of the pump shaft and a catastrophic and expensive failure!!
