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Seek to understand,^Value
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Discussion Starter · #1 ·
Specific question: How to get the viscous fan clutch nut on straight?

I asked in the alternator thread 12 hours ago but nobody responded, probably because it's buried in the details ... but I'm stymied at the moment.

Q1: Is there a nut I can buy that has the same threads so I can "clean up" the stripped thread at the very end of the fan hub (presumably on the waterpump)?

Q2: How can I get the fan clutch nut to spin with the fan temporarily so that I can get the fan clutch nut on "by hand".

DETAILS:
The problem is that the fan clutch nut doesn't spin with the fan and you can't get your fingers on the clutch nut to spin it on the water pump by hand. So you have to spin it on with the 32mm thin wrench.

But, it's heavy, you're holding it from the top, the shroud is in the way, and it invariably goes on crooked! :(

What the trick?

How can I lock the fan to the fan clutch nut temporarily so I can spin it on straight by hand before using the 32mm wrench?

 

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Seek to understand,^Value
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Discussion Starter · #4 ·

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Seek to understand,^Value
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Discussion Starter · #5 · (Edited)
I failed.

It's not that cn90's string-on-the-fan-nut trick isn't spot on; it is! I held the heavy unwieldy viscous fan in one hand and the nut slow spun perfectly with the string!

Cn90's approach felt wonderfully easier than the dismal method I tried yesterday of barely holding the unwieldy fan with the fingers of one hand in the tight crevice and spinning the nut on with the wrench in the other hand in a different slot of the crevice (snapping photos with my third hand and my fourth hand holding the light so I could see at night).

My problem now is that the first thread or two of the water pump is stripped (I can feel the sharp edge with my finger).

If I had the right size die I could clean the threads up a bit (I really do NOT want to do a cooling system overhaul at this time because I just put everything back together!).

I'll wager this is the first time this question has been asked on bimmerfest!

QUESTION:
What is the water pump thread thread size (and where can I get that special die?)

 

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Seek to understand,^Value
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Discussion Starter · #7 · (Edited)
Threads can be straightened out with a thread file.
OMG. I never heard of a thread file before! It sounds like a good idea because it sounds like it might be able to handle reverse threads and forward threads whereas a single die couldn't do both.

Do you think one thread file can handle both reverse threaded and forward threaded threads?


 

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What DHoang said... If you've only damaged the first couple threads on the water pump, chances are you can use a small file to "rebuild" the thread tracks. I'd try that before buying a new water pump. Getting a 32 mm thread die might be expensive and hard to align/use.

I haven't tried CN90's idea (but I like it). I've had good luck so far re-attaching the clutch fan to the WP. I worked from above the installed shroud, with my right hand reaching in and holding the fan as "straight" as I can see, on the WP threads, and my left hand using the 32 mm open-end wrench to slowly get things started. It only seems to take about half a turn for the fan to hold and let me start spinning it to screw itself onto the WP the rest of the way. That's the trouble spot though; it takes me about five attempts but altogether that's less than a couple minutes....persistence pays.
 

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Are you sure the threads are stripped?

If you didn't drop the water pump on it's shaft end ... I would suspect they are fine.

[The water pump shaft thread] Where the thread begins on the shaft, when screwing on the nut/coupler, does not have the same engagement "feel" as a regular nut on a bolt.

I don't use a string when reinstalling the fan.

My method: (use at your own risk ;-) )

1. locate the thread beginning on the water pump shaft visually (rotate to approximately 12:00 position)
2. using both hand, hold fan suspended so that nut on viscous coupling (VC) is square to the end of the water pump shaft (this can be tricky)
3. rotate fan clockwise (thread won't engage b/c is left hand thread) while gently pressing VC Nut against the end of the shaft (pass blades hand to hand)

* You'll feel the nut rotate over the end of the threads (sort of like when you undo a soda bottle cap and it is unscrewed but not off ... if you continue to rotate it .. it "hops" over the end of the thread)

4. once you've gotten to this point, while gently pressing the fan/VC/nut onto the shaft, maintaining it as perpendicular as you can, reverse threading direction (go counter-clockwise) and you should feel the threads start to engage.

5. if they have "caught" = great. spin fan on by hand in a counter-clockwise direction 'til snug. Engine rotation will tighten it after starting.

Good luck.
 

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Ensure you are holding the fan square on the face of the thread, then rotate fan slightly clockwise and then rotate back counterclockwise and spin fan until snug, works for me everytime.
 

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Yes, it's just like fishing, got to hold your mouth just right! I've just gotten lucky after a couple of attempts of holding the fan with my left hand and turning the nut with my right hand using a wrench. If the threads bunged up you could use a small file, called needle files I beleive, to dress them up. I have a set of them in all shapes.
 

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Discussion Starter · #13 · (Edited)
If you've only damaged the first couple threads on the water pump... Getting a 32 mm thread die
Yes, it's only the first thread or two (I can feel the sharp edges).

I don't mind buying a reverse die but I don't know the size.

Do you KNOW that it's 32mm? Do we have any idea on the pitch?


 

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Discussion Starter · #14 · (Edited)
Are you sure the threads are stripped?
Only the first or second thread is stripped. The rest are fine. The string method by CN90 puts no gravity stress whatsoever and spins the nut perfectly; but since the first two threads are toast, it won't spin on straight. :(

If you didn't drop the water pump on it's shaft end ... I would suspect they are fine.
I never removed the pump. I had replaced the alternator (see here). The fan was left in the fan shroud so nothing dropped. I just put the fan nut on crooked the first time (before I learned of cn90's magic string trick).

3. rotate fan clockwise (thread won't engage b/c is left hand thread)
Interesting trick. I'll try that, but, I think I need to clean up the threads first.

Right now I've called Home Depot, ACE, OSH, and none of them have a metric thread file. They have taps and dies, but, I don't know what size die to ask for.

Is it 32mm by ?

 

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Seek to understand,^Value
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Discussion Starter · #15 · (Edited)
Every tool box needs one of these.
Correct, every tool box needs TWO of these (one metric, one SAE). :)

I'm calling around frantically to see if anyone has either the metric thread file in stock nearby or the 32mm left-hand die (not sure what thread pitch yet).

So far, no luck ... am still calling ... even tried the industrial supply houses in San Jose, Granger, namely White Caps, Mister Metric, etc., to no avail.

We should find a good mail-order supply for these thread files ...

 

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Sorry I don't know the exact thread size, I carelessly typed 32 mm because that's the outside bolt/wrench size (d'oh!).

If it were me, I'd just work on one damaged thread at a time with a small triangular jewelers file (about $3 from any jeweler/lapidary supply).


Went and measured the thread on my old WP.....

Nominal OD is 24 mm and thread pitch is 1.5, so ....

M24 X 1.5, I'm guessing.
 

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Discussion Starter · #17 · (Edited)
Nominal OD is 24 mm and thread pitch is 1.5, so ....M24 X 1.5, I'm guessing.
That's what I was looking for! Someone with an old water pump in hand. I have been working in it for the past few hours and did not see your post until now.

I ended up following the Beisan thread for removal of the fan shroud to gain access to the water pump shaft to clean up the threads. I broke a nipple in the process, found a hose about ready to blow, and lost a plastic rivet set; but other than that, it was uneventful. :)

I measured the shaft with my SAE micrometer at 0.939 inches in diameter (23.85 mm) at the outer tip of the threads so that correlates with 24mm which would be 0.945 inches. I also measured a pitch of 1.5 since 1.75 was too big and 1.25 was too small. I didn't know if the reverse (left hand) threads would matter to my pitch gauge or not.

BTW, I called every hardware store in San Jose, Campbell, Saratoga, Milpitas, Sunnyvale, etc., even the construction ones like White Caps, Granger, and Mister Metric, and others ... and none had left-hand dies in stock nor did they have a metric thread file! :(

Almost anti-climatically, with room to spare, I easily spun the fan on straight by holding the fan steady and turning the water pump by hand (pictures to follow). I didn't even have to clean up the threads.

Note: I found this very similar thread searching for information later ... they say it's an M25 (not an M24) thread!

 

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I see you fixed it... anyway

Tried it... did not work well. Gave up on this method. Crawled under the car and threaded it on from below. Still a pain. Remember never ever use a wrench to "help" thread on a fastener or in this case, the fan clutch to the WP. If it can't be done by hand then find out why. Carefully examine the threads on the fan clutch and WP. You can clean the threads on the WP with the proper " thread chaser". I've also used a small triangle file successfully.

Assuming this is a new WP, use you old WP to clean the thread in the fan clutch. One trick is to take a hacksaw and perpendicular to the threads, cut through the threads on the old WP.
Make sure you do not do this where the thread starts on the end. This acts a bit like a tap.

Good luck.
 

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Hose about to blow, huh? Then your troubles with the clutch fan may have been a blessing in disguise.

As to thread pitch etc., if you end up finding a reverse-thread M24x1.5 die, chances are it will cost more than a new water pump with pristine threads.

If you already got the clutch fan nut on the WP straight by turning the WP, my question: Do you have the main belt off?
 

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Discussion Starter · #20 · (Edited)
Do you have the main belt off?
Yes.

Previously, I had the new alternator back on, the new tensioners back on, both new belts back on, and I was just putting the fan back on when I damaged the first or second thread on the water pump, causing the fan to always screw on crooked.

I think it went on crooked because I had so little room, and, therefore, against my own better judgement, I used a 32mm wrench to spin the nut on as I didn't know about the two "tricks" known to me now:
TRICK 1: cn90 string on a nut method
TRICK 2: Turn it the wrong way first (to trick it); and then the right way

Anyway, at this point, I've put the nut on and off a few times and it seems to go on correctly. But, I broke a nipple in the radiator and I found a hose about to blow (pictures taken but will post soon) so methinks I'm looking at an impromptu cooling system overhaul. Only I don't have any parts. :(

 

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