Fan belt help

[twaldron]

I picked up a new Contitech fan belt from Zims Autotechnik in Texas who insisted that this was the replacement belt to use. The new belt measures 10x725 while my old belt measures 9.5x725. I cannot get the sixth shim on the shaft. I've tried for hours to compress the belt to get the last shim on and now my thumbs are bloody pulps.

Is this really a proper belt and I'm an idiot or do I need to go back to the 9.5mm?

Specs: 1978 911SC

[Scott R]

How many shims are you using the inside, and how many on the outside?

[Gogar]

The Pelican catalog lists 3 sizes, 10x710, 9.5 x710, and 10x725. I know I have 10x710 and it works fine. I'm short a shim, though!

[twaldron]

Originally Posted by Scott R

How many shims are you using the inside, and how many on the outside?

When I took off the 9.5mm belt, it had two on the inside and 4 on the outside. Since the 10mm is fatter, I was going to try 3 and 3.

[Scott R]

Originally Posted by twaldron

When I took off the 9.5mm belt, it had two on the inside and 4 on the outside. Since the 10mm is fatter, I was going to try 3 and 3.

Start with one shim, and as you do this spin the fan a little to get the belt over the pulley surface, it should slip over given the rotation.

[twaldron]

Originally Posted by Gogar

The Pelican catalog lists 3 sizes, 10x710, 9.5 x710, and 10x725. I know I have 10x710 and it works fine. I'm short a shim, though!

I saw that listing for the 10mm, so I'm trying to figure out what I'm doing wrong. I just cannot get that last shim on there. I'm thinking the 9.5 would fit the last one OK, but if half the world is using the 10mm, I should be able to get it on, right?

[Scott R]

The 9.5's are getting hard to get for some reason, but I ca tell you that the one you have will work. I have a 9.5 on my fan now, however my spare is a 10, and I've had it on before.

[twaldron]

Originally Posted by Scott R

Start with one shim, and as you do this spin the fan a little to get the belt over the pulley surface, it should slip over given the rotation.

I'm not exactly sure what you mean here. The belt is seated in the bottom pulley and in place at the top as I put the half pulley on the shaft. I've been putting LOTS of pressure on the pulley while turning the fan to try and compress the belt a bit more (or push it up out of the way) but that last shim still has nothing to 'hook' onto. If the shims don't seat properly, they will crush and the pulley will be wonky (technical term).

[Jim Sims]

"I cannot get the sixth shim on the shaft. I've tried for hours to compress the belt to get the last shim on"

Perhaps you require clarification on how the shims work. All six shims should always be installed but some may go between the fan and the outer pulley half and the balance go outside of the outer pulley half under the domed (cupped) washer. Sufficient shims should be placed between the pulley and fan to establish correct belt tension: more shims here accomodate a shorter belt and fewer shims a longer belt. Whatever shims remain are then stacked on the outside of the outer pulley half (this is important to keep the alternator shaft domed washer and nut from "bottoming out" on the shaft features). If you have all six shims on the inside between the fan and outer pulley and the belt still won't fit then you likely have the incorrect belt or one that is "out of tolerance" - too short.

[twaldron]

Originally Posted by Jim Sims

"I cannot get the sixth shim on the shaft. I've tried for hours to compress the belt to get the last shim on"

Perhaps you require clarification on how the shims work. All six shims should always be installed but some may go between the fan and the outer pulley half and the balance go outside of the outer pulley half under the domed (cupped) washer. Sufficient shims should be placed between the pulley and fan to establish correct belt tension: more shims here accomodate a shorter belt and fewer shims a longer belt. Whatever shims remain are then stacked on the outside of the outer pulley half (this is important to keep the alternator shaft domed washer and nut from "bottoming out" on the shaft features). If you have all six shims on the inside between the fan and outer pulley and the belt still won't fit then you likely have the incorrect belt or one that is "out of tolerance" - too short.

As I posted above, there were 2 on the inside and 4 on the outside with the 9.5x725 belt. I would assume that replacing with the same belt would require the same distribution of shims, unless the system was adjusted for a stretched belt at some time.

My new belt differs in that it is wider by one half millimeter but is the same length. I was guessing that the wider belt might require an additional shim on the inside and was trying to go 3 and 3.

Regardless, I don't seem to be able to fit 6 shims and a 10x725 belt on the shaft. The distribution of the 6 shims doesn't affect this problem. Am I missing something?

[Jim Sims]

Check if the fan has shifted rearward toward the end of the shaft due to a spacer washer or woodruff key shifting. Can you install all six shims without the belt in place?

[Gunter]

Jim said it.

Watch that woodruff key and try without the belt first.
The outer half of the pulley has that special cut-out seat.

[dm36415]

One of the best tips I received on this board was using some fishing line to tie together the shims on the outside, keeping them together. Worked like a dream, and saved me hours of frustration trying to get that last shim on.

[dimeified]

Originally Posted by Gogar

The Pelican catalog lists 3 sizes, 10x710, 9.5 x710, and 10x725. I know I have 10x710 and it works fine. I'm short a shim, though!

You really shouldnt drive without the 6 shims. The pulley wont clamp tight to the fan even though it seems to, and the pulley will wobble. After a while, the center of your pulley will break creating jagged edges inside it. Before you know it, when you hit the gas, those jagged edges cut into the fan like a chainsaw. If you keep ignoring the strange sound this makes, you'll eventually find yourself replacing not only your fan, but your alternator too cause you also cut through the shaft as well as the fan. And if your real smart, you'll order only the fan, then when you pull everything apart to replace it, you'll THEN find out you need a new alternator, and have to wait another week to get THAT in. Then you'll be cursing out your car for YOUR mistake. Finally when everything is back together and in proper working order, you'll pat yourself on the back for doing it yourself. Then you wont tighten the fan strap tight enough, and the housing will slowly move back into the crank pulley. Luckily you checked your work often, and found it very soon and were able to correct it. But yes, 2 weeks of waiting for parts, doing the labor, and all the $$$ you spend on a new fan and alternator is the result of NOT USING ALL 6 SHIMS! Ask me how i know?

[twaldron]

Originally Posted by Jim Sims

Check if the fan has shifted rearward toward the end of the shaft due to a spacer washer or woodruff key shifting. Can you install all six shims without the belt in place?

Yes, everything is a-ok and fits fine without the belt in place. I'm a little unclear as to how the Woodruff Key fits into the fitment of the outer half of the pulley. As I understand it, the pulley just seats on the shaft which is squared off to match the center hole in the pulley and there is no other key way. Is there something else that helps it seat?? I've got it installed now so I can't look at it. Just wanted to make sure I'm not missing something when you guys are talking about key ways.

After mulling over Jim's reply regarding how the shims work, I decided to rearrange them and put 4 on the inside for the fatter belt and 2 on the outside and was able to hang the last one on.

After tightening everything else up, I tested the taughtness of the belt with my now very tender thumb and registered about 1/4" of play. I think the belt could be a touch tighter, but it may be in the realm of OK. The belt vibrates a little at idle (not the pulley) at least a bit more than the A/C belt, which is longer and also has 1/4" of play.

I ran it for a bit, took it out and ran it through some paces and it seemed to stay put. My shop manual calls for .2" of play which is 1/5". What do you guys think?

[Jim Sims]

Provided the outer pulley half is on squarely (no eccentric wobbling) and the belt doesn't squeal when shifting or when the engine is cold you should be fine.
The belt deflection distances are only approximate unless given and then measured with a controlled amount of force.

[twaldron]

Well, I guess I'm going to call this project done then. Why is it always the simple jobs that cause the gray hair? Thanks everyone for their help and input!!

tw