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Problem water pump Yanmar 2GM
"Jeffrey P. Vasquez" wrote in message . 17... Your diagnositcs seem to point clearly at a pump issue. More further on - Okay, not just *very* familiar, but spot on exact. However, if I am understanding your description, it seems you were in the act of rebuilding or partially rebuilding the water pump prior to the fault? Is it possible that simply opening the back plate, removing the worn impeller (worn, but no missing vanes), installing a new impeller, replacing the gasket and replacing the backplate could result in the sudden occurrence of this shear issue? Could the friction generated by the fresh rubber of the new impeller (and possible dry running, though the engine manual says dry-running will destroy the impeller in seconds, which it didn't or wasn't) have caused a shear issue between pulley and shaft where none existed before? Possibly. You didn't mention removing the cam, so I'm assuming that's still in place. Depends on your gasket thickness, the length of your replacement impeller, and how stiff it is on the shaft. Too long an impeller, or too thin a gasket (or both!) can cause the impeller ends to seize against the cover plate once the cover is tightened up. At the next start, the shear occurs. Also, if the impeller is a very tight fit on the shaft, it may be pushed in too hard and jammed against the back plate, or it may be standing a little too proud and jamming against the front plate. At the next start . . . Missing out a gasket obviously also has the same effect. With a raw water only system you'd overheat pretty quickly. Your test separating the pipe at the engine block and seeing no water entering the block eliminates the most common blockage problem, which is the slow build up of calcium and borate salts in that areas which regularly cycle through hot and cold. Also, this type of build up is over the years, not days! Sorry you're not having fun! Barked knuckles, hacksaw mashed screw slots, lost screws in the bilge drains and used diesel oil deodorant and finger colouring does all seem to be all part of the game. No wonder my wife tells me not to hand the bread to our visitors! I have read that water flows through the water pump without rotation of the impeller. Not significantly. You'll get a drip rate around the backplate and endplate if there's a positive pressure, more with wear. Any more and the gasket's too thick or the impeller too short (opposite to the seizure problem). This leakage is trivial compared to the pumping capacity of the vanes. -- JimB Yacht Rapaz, sadly for sale: http://homepage.ntlworld.com/jim.bae...cification.htm jim(dot)baerselman(at)ntlworld(dot)com |
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