Water Pump e24 Cast iron vs pressed steel impeller

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jeme9
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Water Pump e24 Cast iron vs pressed steel impeller

Post by jeme9 »

I received my replacement water pump for 1979 e24 635csi M90 (#5550216). The part number ordered was 11511705236 (part I received was labeled 11511705273 I don't believe an issue).
However, the pump has a pressed steel impeller rather than a cast iron impeller on previous pump (refer photo, new pump on right is still in bag so not totally clear).
Has anyone had problems with steel impellers, life / cooling issues etc ?
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zinnocoupe
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Re: Water Pump e24 Cast iron vs pressed steel impeller

Post by zinnocoupe »

I've installed a few water pumps and they've always been the solid cast brass impeller. Everything I've always read says the cast metal is better than the plastic or pressed one. Where did you get it and what brand is it? You have to wonder if they use a cheap impeller whats the bearing like? I would recommend returning it and getting one with the cast impeller. My 2 cents
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1979 Euro 635ci no longer a basketcase, just a running rust bucket!
1977 530i Partially restored and running now!
1987 635csi 60K KM Garage Queen
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sansouci
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Re: Water Pump e24 Cast iron vs pressed steel impeller

Post by sansouci »

I'd be curious about the drain and replace cycle for your antifreeze given the corrosion on the impeller. I read an interesting sales pitch for a power flush device for cooling systems that promotes the idea that floating corrosion particles cause the wear on the pump bearing leading to leaks and failure. As my car is not a daily driver, I wonder if the exhaustion of the anti-corrosives is more due to time (as it relates to galvanic action) or heat/cooling cycles.
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84 E24 633Csi Auto, Bronzit/PearlBeige 6997510
93 E32 740il M60 Auto, Alpenweis/Ultramarine
60 528i M30 5-speed Green/Beige (crushed)
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Brucey
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Re: Water Pump e24 Cast iron vs pressed steel impeller

Post by Brucey »

in theory a well-shaped cast impeller ought to be better than a more crudely shaped pressed steel impeller. In reality the surface finish of the pressed steel part is smoother and the swept area for flow is larger too. If there is a difference I'm dashed if anyone can actually tell.

A similar consideration applies to alternators; originally the air cooling was assisted by a nice cast impeller behind the pulley, (which even had variable pitch blades so it didn't resonate) but this was quietly replaced by a pressed steel item. No one noticed; in fact the later alternators with the cheap steel fan had a higher output in most cases, too.

cheers#
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