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Old 10-15-2012, 10:54 AM
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hornhospital hornhospital is offline
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Oh, the joys of water pump replacement!

A friend of mine bought a 1984 633CSi recently, non-running. It didn't take much to get it going again. One of the things that needed attention was the leaking and very noisy water pump. It was rattling and grinding pretty badly.

I pulled the radiator, fan, hoses and other stuff out of the way, then began removing the water pump bolts. I sprayed all of them with penetrating oil and let them soak over night. The next morning all of them made that satisfying "click" on the first tug of the wrench, then loosened....all except for the bottom one (of course...there's got to be one!). It made the sickening 'oooze' of a quarter-turn and then the head snapped off. To be honest, it was expected. In fact, i was amazed that more of them didn't break. They were all pretty badly corroded, but the bottom one was firmly seized in the pump body as well as the threads. After a 30 minute struggle to free the remaining body of the bolt from the pump body I finally resorted to breaking it off. It left a tiny nub of the threaded body sticking from the block. It was unreachable with pliers. After determining that the only option was to drill it out and pray I could preserve the threads (or failing that, put a thread insert in it), I took out the nose grills, the passenger-side grill, the passenger side horn, and after vacuuming the A/C lines, the A/C condenser. I could then get a straight shot at the remains of the bolt. Boy, it's a long reach from the nose of a shark to the water pump mounting point on the block! I carefully center-punched the bolt nub, and starting with a much smaller than tap-drill-size bit (I think I used a #25 to start) I drilled through the bolt until it went through the bottom tip of the bolt, but NOT through the bottom of the threaded hole. I stepped up to a slightly larger bit and repeated the drilling, then went to the tap drill size (#9 bit) and slowly drilled out the bolt. All that was left was the coil of threads of the bolt, which I picked out with a scriber. After that I took a M6 x 1.0 tap and cleaned out the threaded hole, tested the fit with a new bolt, and then cleaned up all the gasket surface. The new pump went on without a hitch, and the rest of the parts were reassembled in about an hour. I filled the cooling system with fresh BMW antifreeze and distilled water after flushing out the Prestone someone had put in it previously, and after bleeding the system I took it for a drive. No leaks, no overheating, and no noise from the pump!

Now on to the rest of the million things that need attention on this car. Three big boxes of suspension, engine and electrical pieces from Pelican are going to keep me busy for a while.
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1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette"

Last edited by hornhospital; 10-15-2012 at 12:42 PM.
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