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Seek to understand,^Value
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25,199 Posts
Does anyone know the TAP size to clean the threads on the water pump shaft?

I didn't know about this wonderful trick until it was too late.

The last thread or two of my water pump shaft is "sharp" to the touch, such that the fan nut is going on crookedly (details here and here).
I'll bet this next question has never been asked on Bimmerfest before ... but I need to know ...

Q: Do you know what the tap size is for the water pump shaft threads?

BTW: Below is a pictorial DIY of cn90's suggested method. It failed for me, but, only because I had already stripped the last thread or two of the water pump shaft NOT using this method! :(






 

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Registered
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33 Posts
That's awesome. I just did the full cooling overhaul and they say the first step
and the last step (dealing with that hex nut) are the hardest. They turned out
to be the easiet thanks to that trick. I used kite string and duct tape.
*
now I just gotta deal with air in the system. Everytime no matter what I try
I always get it.
 

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Premium Member
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5,938 Posts
I was amazed I guess or maybe just lucky but I was able to just grip the fan on both side and spin it right on the nut to start it*...then I just spun the fan to tighten it as much as possible and threw the 1 1/4" wrench on it to tighten it a tad more. Just let the engine to the rest over time. :)

* - Okay, I tried doing it from above for a few mins...then below for a few mins...then I was going to try the string trick and decided to try it from above again and son of a gun, spun the sucker right on. Lucky me. :)
 

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Seek to understand,^Value
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25,199 Posts
I should mention, as an update, that I used the rawhide trick a few months after my posts above (when my cooling system blew up) and everything worked out perfectly!

I gotta' thank cn90 for this great idea.

Just for the record, notice Rexgo used dental floss for his cn90 fan clutch nut trick:
- Rexgo's '97 528 Cooling O'haul

An advantage of the rawhide is that it's easy on the hands; an advantage of the dental floss is that there's no need to tape it on.
 

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Resuscitating Touring
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8 Posts
great tip CN90!
i just replaced my fan clutch and this was such an invaluable tip.
for those on the electric fan camp, this fan clutch keeps air over all plastic parts which prolongs the pliability of the hoses.

btw, how viscous is the clutch fluid suppose to be?
neither my old one nor the new one (non-OE) are spinning as freely as these guy's videos below.
these guys are able to stop the fan with a finger.

i am able to spin the fan when the engine is off but there is resistance. and when idling, there is no way i can try what these guys have shown.
although i did notice in both videos, they have V8's and mine is an I6.

 

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167 Posts
Thank you. Simple genious

Thank you for posting this simple solution. I tried it and it worked perfectly on the second try. ON my first try, I wound the string to pull in the wrong direction. Otherwise it was one pull and done. It was so refreshing to get something to work this well during a cooling system rebuild where I received a dented radiator in a perfect box, broke a thermostat bolt using a torque wrench, dropped the PS reservoir nut into the abyss, and discovered a crack in the bleeder vent after all was installed. Oh yeah, my work was interrupted by rain 3 times.
I can't wait to pass this trick on as mine.
 

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Seek to understand,^Value
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25,199 Posts
I used this idea with string and it was very easy
I must agree this string idea is fantastic!

Anyway, I came here just now to cross reference an interesting test by Teklord69 who has been driving a while now, as a test, without any fan clutch whatsoever, and, who has "modified" his fan shroud, for each on/off of the fan clutch itself:
- My new fan shroud "mod"
 

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Otto Zwei-Punkt-Null
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3,522 Posts
This trick will be incredibly useful. Thanks for the post. I will be using this tomorrow when I do my fan clutch.
 

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1 Posts
I know this is an old thread but I am new to this forum and just discovered this tip. I must say after 1/2 hr of frustration trying to thread the fan hub back on the water pump, this ingenious idea worked in about 2 minutes. Thanks for the excellent idea for getting this fan back on!
 
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