How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

[Mark F.]

This is a followup to a Mike Ernst post regarding balancing marks on original engines.

https://www.forums.ncrs.org/showthread.php?132505-GM-went-to-great-pains-to-get-them-smooth!&p=933786#post933786

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[Bill B.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Hi Mark,

The 1972 Service manual has a procedure whereby you use a dial indicator on the Fan blade spider, close to the clutch and while the fan is clamped to a fixed point (i.e. fan shroud or upper control arm link), one slowly rotates the water pump pulley in one direction noting and marking the high and low points of the readings. The indication of 0.006" total deviation or less is good. If greater, then it will need shims placed behind the fan clutch hub to pulley interface. Pgs 6K-4 and 6K-5 detail that procedure. If you need the procedure, I can photo it and place on this thread. I made my shims out of aluminum foil. They worked! Patience is key, as some trial and error may be expected before getting almost perfect results.

If the pulley itself is wobbeling just as bad as the fan/clutch assy, then you may have a Water Pump shaft issue. If you can take your hand and wobble the assembly (belts removed), then the procedure above is null and void.

If no hand wobble (looseness), then you might be able to shim between the pulley and the water pump hub, but that's more work and probably not recommended.

[Mark F.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Bill,

Thank you so much !
I get exactly what you're saying and would greatly appreciate that description in the '72 SM.

There is absolutely no movement on the water pump shaft - and as a matter of fact, I had the front end of the car moving ever so slightly as I was exercising the pulley with my hands...

I'll also try to find any of the balancing marks Mike mentioned in his other post

thanks again...

[Bill B.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Here is the procedure (hope the pics come out oriented correctly).
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[Richard M.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Bill I rotated them. Thank you for this information. I never saw this procedure before.

Rich

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[Mark F.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Hi Mark,...The 1972 Service manual has a procedure whereby you use a dial indicator on the Fan blade spider, close to the clutch and while the fan is clamped to a fixed point (i.e. fan shroud or upper control arm link), one slowly rotates the water pump pulley in one direction noting and marking the high and low points of the readings. The indication of 0.006" total deviation or less is good. If greater, then it will need shims placed behind the fan clutch hub to pulley interface. Pgs 6K-4 and 6K-5 detail that procedure. If you need the procedure, I can photo it and place on this thread. I made my shims out of aluminum foil. They worked! Patience is key, as some trial and error may be expected before getting almost perfect results...

Hi Bill and Rich,

PS - I forgot to say that the '67 Chassis SM makes no mention of this in the same section (6K) as the '72 Bill shows...

[Richard M.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Hi Bill and Rich,

PS - I forgot to say that the '67 Chassis SM makes no mention of this in the same section (6K) as the '72 Bill shows...

Yes that's why I never knew about it. I don't have any C3 CSMs.

Rich

[David Z.]

Re: How to fix (balance) Fan, Fan Clutch, and Water Pump Pulley Assembly Wobble ?

Made a "1-pager" out of the info. The link in the PDF version (but not the jpg) takes you to the TDB thread.
Dave Z

Thermostatic Fan Clutch 1972 Service Manual.jpg