How many shims?

TeeJayHoward · 01:55 PM

Hopefully this is the right subforum for this, if not, please let me know and I'll petition a mod to move it.

My fan/alternator belt fell off today. Then it fell off again after I put it back on. Then a brand new belt came off. Then the new belt came off again. It wasn't until the fourth time that I finally broke down and compared the parts I had in hand to the pictures I found online. That's when I discovered that my half-pulley was not supposed to have a round hole in it - It's supposed to have a key'd square/circle combo thing. And from what I can see, the fan itself isn't supposed to have grooves in the shaft. Grooves that suspiciously match up with the width of the half-pulley!

Also, I KNOW I put shims in there - the exact amount that were on the car when I bought it, in the same places. But somehow, they got turned into metal shavings when the half-pulley decided to exit this world. Unfortunately, I didn't write down how many and where they were. I just plain didn't anticipate I'd ever need to build it up without a reference.

So...

How do you tell how many shims to use in between the fan blades and the half pulley, and how many to use in between the half pulley and the tensioning cap? It can't always be a fixed amount, or else there would just be a single washer of the appropriate thickness. You use shims to adjust as needed, but... I don't know how to tell what's needed!

Help me out, shade-tree experts! How do I tell how many shims I need, and where?

edit: Oh yeah, and replacement parts are coming. Fan, shroud, half-pulley, shims, and belt. The whole shebang. Heck, I might even use this as an opportunity to install a new alternator.

TimT · 03-08-2022, 02:10 PM

6

The distribution of the 6 between the inside of pulley half, or the outside is determined by belt tension

TeeJayHoward · 03-08-2022, 04:13 PM

Quote:

Originally Posted by TimT

6

The distribution of the 6 between the inside of pulley half, or the outside is determined by belt tension

Is that all it is? OK, now I feel like a fool. Thanks, Tim!

stownsen914 · 03-09-2022, 04:21 AM

It looks like the mandrel on the fan has been damaged by the pulley spinning. It looks rounded at the base. This can happen when the pulley comes loose, and needs to be fixed or the pulley won't be held in place correctly.

gled49 · 03-09-2022, 06:45 AM

The fan hub is damaged. The fan with hub, or the hub needs to be replaced or welded/repaired.

Walt Fricke · 03-09-2022, 11:48 AM

My first thoughts also. This a rather common issue when there aren't enough shims, or the nut isn't tight enough. With too few shims, tightening the nut distorts the cup washer, and eventually it doesn't press everything together properly. It is the friction between the mating surfaces which keeps the outer pulley half solidly linked to the inner half, not the squared off sort of keyway (mandrel). At some point, the cup washer can get almost flat. So the outer half of the pulley machines that groove in the keyed threaded part. Something like that, anyway.

There have been several posts about this, including ways to fix the damaged part of the fan (no, JB Weld won't work, it seems).

But TeeJay noted that he isn't trying repairs, and has ordered the obvious replacement parts.

Not sure why he has a replacement shroud coming, but now that he knows the deal with the shims, he has what he needs.

TeeJayHoward · 03-11-2022, 07:53 PM

Quote:

Originally Posted by Walt Fricke

Not sure why he has a replacement shroud coming, but now that he knows the deal with the shims, he has what he needs.

I believe mine to be damaged by the terrible fan that was in there (two blades have large chunks taken out of them). There's also a crack, hard to see, just above the scrape marks. I'm not sure if it's deformed or what, but... I really am just getting a new shroud because I think the Rennline ones look pretty sweet and I am going to be in there anyway.