The water pump as used in the OH series engines of the CS8 and PU models presents a few traps for the uninitiated . I have worked out a method of disassembly that is different to what the manual recommends , this was done to avoid damage to the brittle cast iron impellor . After I smashed a impellor while trying to remove it with a three legged puller , I devised this alternative method and it worked quite well . Step 1. Remove the castle nut and pulley as per the manual . Step 2. As the tapered pin holding the impellor is normally rusted in , I carefully drill out the pin using a bench drill , being carefull not to drill into the shaft , just deep enough to weaken the pin . Step 3. Remove the front ball race and bearing spacer . Step 4. Remove the circlip that locates the rear thrust ball race . Step 5. The shaft is now pressed out of the impellor by using a shop press . The front edge of the housing sits on the press base as the shaft is pressed out vertically . The four vanes of the impellor will be supported against the rear face of the housing as the shaft is removed . Using this method , the carbon seal locating pin on the shaft is sheared off in the process , this is unimportant and easy to replace . Some heat applied around the impellor shaft area helps to loosen the impellor . I used a grinding stone ( engine valve type ) mounted in the bench drill to reface the housing seal face Re - assembly The design of the water pump is such that the rear ball bearing , a thrust type, has no apparent pre load on it , it floats on the shaft and is located by a circlip . The rear thrust bearing can be replaced with a plain ball bearing of the same type as the front. This replacement bearing will provide a better end float condition eg. there is no end float as is the case with the thrust type bearing . The modern replacement bearing is number 6302 , a common type easily available . To use a 6302 to replace the rear thrust bearing approx. .6 mm needs to be ground from the outer face on one side . The original thrust type bearing has a width of 12.2mm wheras the 6302 is 13mm wide . The replacement 6302 bearing is located by a circlip which will not fit until the outer bearing face is ground down on one side The shaft will be located approx. 1/32 " further forward , this does not present a problem . I used a carbon seal from a side valve Ford V8 water pump and ground off the locating tags . A new rubber seal was made up from a modern mechanical seal as used in a swimming pool pump . Some improvisation is needed to make the swimming pool seal fit eg. I had to disassemble the seal and modify it slightly . Mike . |
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