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74 620: Fan bolts loosened, pulley hammered and chopped them off, destroyed radiator

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Bolts put 1/2" hammer circumferential slots in pulley until pulley finally chopped them off.


MY FAULT since I had the fan off:  I THINK the bolt head safety tabs were rusted to nothing so I THINK I put the bolts back in with washers and Locktite.  




PULLEY:  I have to either 1) find a used one, or 2) drill 4 good holes in it.   I suppose I could use the plastic fan as a "nut plate" but plastic does not make good nut plates.  Also I'll have to make a mandrel to align the fan on the pulley.


SECURING BOLTS:  How to install so they don't loosen again.  Frankly I could see the plastic shrinking and contributing to their shrinkage.



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I can't wait, it's my daily driver and I just totaled my backup (87 Turbo Sprint).


My main concern now is how to be sure those bolts don't loosen again.  Which is further exacerbated by the inherent vibration of the engine.  It looks like those lock strips area available but I think I have some stainless I can make some from.


What really bothers me is that plastic creeps.  I would expect that over the years that clamping force will subside but maybe the use of lock washers might help to keep the clamping load sufficient if the plastic shrinks a few mils.


If I had some safety wire pliers, I'd learn how to do a nice aviation safety wire job.


But one way or another, I think I'm putting JB Weld between the pulley and water pump flange just for some extra protection.


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1 hour ago, Ooph! said:

Were they the original bolts? running it without the fan using electric? 

I've seen things like that happen when a bolt is tightened against the shank making it appear to be tight but its not.

They looked like original bolts.  The problem is you cannot tighten a bolt head into a plastic fan as tightly as a metal fan.  So you have to use some kind of locking mechanism - the OE is a sheet metal tab that you bend up against the sides of the bolt head hex.  Safety wiring would also work.  My concern is the dimensional stability of the plastic.  If it shrinks over the decades, the bolt clamping force reduces and who knows, maybe the pulley can start moving around and start hammering the bolts.


I have a new OE brass radiator that is going in and there is NO WAY I'm going to let that fan destroy an unobtanium OE radiator.

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It just occurred to me that the "monkeys" that worked on this truck before me (like the plywood MonoJet adapter cut out with hammer and screwdriver may have the wrong plastic fan on this engine.


The reason I say that is the pilot hole ID on the fan is smaller than the pilot hole ID on the pulley.  One would think the fan and pulley would have the same pilot diameter. 


Tomorrow I will see if the pump has a 2-step flange that matches those 2 diameters.


Right now, I'm betting I have the wrong fan on the engine.......   (that would be par for this course....)


EDIT:  carpartsmanual shows the "washer locks" being circular while the ones on the fan were straight.  I also found the CPM part number 21069-21000 are straight.


Here are pics of the front of the fan and a closeup of the rear or the hub:



Edited by Cardinal Grammeter
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Just redrill new holes in the hub and use thin strips of metal which will allow a tighter torque against the plastic and can be used to lock the bolt heads. I don't think shrinkage is a factor as these have stayed on stock 521/510 for decades. Skip the JB.

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I just checked the water pump flange and there is only one pilot diameter.  So there is no way to explain why the fan and pulley have different pilot diameters - either the pulley pilot is too big and loose or the fan is too small and binds.


I won't have dimensions until I remove the shroud and radiator to make room.


I should be updating this reply throughout the day since is my primary task right now.  My next step is rounding up the new radiator and I think I had also acquired a stock fan and shroud to - at least the shroud which I remember as being metal (the new radiator had a plastic one) and I think I got a fan blade too.  (The shroud and fan will be harder to find since I know exactly where the radiator is.)


Here is a pic of the radiator damage and the head of a sheared off bolt - it is fully threaded so there was proper clamping when I assembled it when I replaced the radiator some years ago.



Edited by Cardinal Grammeter
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What an idiot!  I could have welded up those slots!  Talk about losing sight of the trees for the forest.


Well I do have to replace the lower radiator hose and either put the L20B shroud in or find the proper one I've misplaced.


Now those DAMN SAFETY TABS are in the way.....

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