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hornhospital 10-15-2012 10:54 AM

Oh, the joys of water pump replacement!
5 Attachment(s)
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. :mad: 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! :thumbup: :roundel:

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. :thumbup:

PETER NEWMAN 10-16-2012 10:29 PM

Water pump bolts
When I replace water pumps I always cover the bolts including the threads with copper ease and they will never seize again, PS When you remove the viscouse fan coupling you MUST never lay it flat, ALWAYS keep it upright or it will fail soon afterwards, Peter

hornhospital 10-16-2012 11:25 PM

Hi Peter,

Yes, I put anti-seize on the bolts, but I used zinc dust petrolatum anti-seize, coating the entire bolt body. It's made specifically for aluminum applications. The water pump body is aluminum, and one of the worst materials you can put between steel and aluminum is copper. It actually induces electrolysis. I work with antique air horns ( that were assembled 50-60 years ago with little regard to later disassembly and know well what happens when a steel bolt is put in an aluminum casting with no corrosion protection.

That's the first time I've heard of possible damage to a viscous fan clutch by laying it flat. Could you please explain why that's bad? What's it do to them?

I've been removing and replacing viscous fans from all sorts of auto engines, not just BMWs, for the last 30-ish years and never had even one fail after being laid flat and then put back on the engine. The latest one that I can tell you exact mileage on is my daughter's E36 318is. The radiator, thermostat, water pump and hoses were replaced at 193000 miles. The fan clutch wasn't replaced, since it tested good (relatively free-wheeling at ambient temp, but firm resistance at elevated temp in the airflow through the radiator). It now has 240000 miles and the fan clutch is still fine, doing it's job as it was designed to do. I can't see, from personal experience, how that would hurt the mechanism. In fact, how do you suppose they ship the clutches? They don't ship them standing up. :dunno:

PETER NEWMAN 10-17-2012 12:35 AM

Water pump bolts
Hi there, I accept what you say about copper and aluminium seizure but I've never come accross a problem using it. Re viscouse fan couplings, If you buy a German Sachs coupling which is original BMW factory fitment it shows very clearly on the box that it must LAY FLAT during pre sale storage, Once fitted and the fluid inside is in it's working position it must never be laid flat if removed from the engine, I've been working on BMW's since 1972 and in the UK it is general knowledge that you never lay them flat because they will not work properly afterwards as I have found out, Peter

BMWFatherFigure 10-18-2012 11:25 PM

I have learned. Just as well you (we) can do stuff like this - the term 'mechanical write off' springs to mind. Have you tried the Snap-On thread restoration set? I swear by mine.

hornhospital 10-19-2012 07:51 AM

I have the "old machinist's" version of the thread restoration kit: a set of letter and number drills, a very good center punch, a set of SAE and Metric taps, and lots of prayer. Yes, I know a standard cutting tap isn't the best for restoring threads, but if done right, it works fine. The main thing is to get all the pieces of the old bolt and all the corrosion out. I was a journeyman machinist for 27 years in a high-precision shop that handle nothing but stainless steels and exotic alloys. Drilling out a plain steel bolt is cake compared to my old job. The hardest part on the 6er was getting access to the thing so I had a straight shot at drilling and tapping it! :D You don't realize just how far back in the front end the block sits until you have to reach it through the grill. I thought I was going to have to remove the entire nose!

I just did some research on the Snap-On Rethread kit.... the identical kit made by the same supplier at half the price ($63-ish vs. $119 as the last listed price for the SO) can be had from Sears. BTW, neither Sears nor Snap-On warranties their tap and die and rethread kits any longer. The have a disclaimer stating they are "wear items". SOME Snap-On dealers will still honor their warranty.

BMWFatherFigure 10-20-2012 04:54 AM

I feel like a knuckle-dragger in comparison. No Sears here so I have to make do with SO. At least he comes to me.

hornhospital 10-20-2012 09:46 AM

:rofl: That was the Snap-On guy's counter to my question of "how are your tools better than Sears since they're guaranteed for life ?" (back when Sears tools WERE good quality stuff....not so much today). His reply "we deliver". :thumbup:

BMWFatherFigure 10-22-2012 06:25 PM

Although I've spent a large fortune on hand tools I now see that I will need electronic 'tools' to continue my obsession. I've heard that some will use a laptop to access. Are there any you can recommend?

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