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Water Pump Type?

Posted: Thu Feb 13, 2020 1:32 pm
by REman
Was wondering if anyone can tell me if this type water pump is considered with threaded hub or without? Need to order water pump and Rock Auto confusing me.
It's from my '81 E12, thanks.

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Re: Water Pump Type?

Posted: Thu Feb 13, 2020 8:18 pm
by HB528i
It is not a ‘spin on’ with the large single nut, it is the earlier ‘bolt on’ which mounts to a riser/nose piece, I can see the small mounting bolt in front of the fan.

Re: Water Pump Type?

Posted: Fri Feb 14, 2020 1:16 pm
by REman
hey thanks for the tip, that's what I thought too and a little surprised because it is an '81 model and should have had the spin on which I've heard is the newer better design.

Re: Water Pump Type?

Posted: Sat Feb 15, 2020 9:43 am
by janusz200
Looks like same design as in my 635 CSi 1980. See pictures - they explain how pump - puley and visco are connected together. Connection between visco and pulley disenables to use newer type of visco with internal thread.

Re: Water Pump Type?

Posted: Sat Feb 15, 2020 5:48 pm
by HB528i
REman wrote:
Fri Feb 14, 2020 1:16 pm
hey thanks for the tip, that's what I thought too and a little surprised because it is an '81 model and should have had the spin on which I've heard is the newer better design.
I think the spin on is a much later design.

Re: Water Pump Type?

Posted: Mon Feb 17, 2020 8:49 am
by keehn
Yes, spin-on is the improved, later design. The spin-on's are reverse-threaded, so as our engines rotate clockwise, so the fan will naturally tighten down on the threads as it spins.

A tip: Should you go with the later spin-on, tighten the fan LOOSELY. That way it will be easier to remove, come time to service your belts. I have done this with ALL of my spin-on Bimmers and have NEVER had an issue with the fan. Every time you rev your engine, you are applying torque to the fan screws, so manual tightening is redundant.

The issue with your (and mine - I have the same setup) setup is that the bolt tightens CLOCKwise; Meaning that if the bolt was loose, there is nothing to prevent it from backing completely out, and BOOM! blades of death destroy your radiator, belts, and dents your hood!

I'm replacing mine with an electric fan that I'll attach directly to the radiator.

Oh, if you elect to keep your current fan, I would suggest using at least Locktite blue, but preferably red, on the threads. Also, check the tightness of the bolt every fill up when you check your oil level (you do check your oil levels at each fill up right? :wink: ).

Mike