Replacing Belt - I think I am missing a shim.

[Emission]

As I get braver working on my car...

I decided to change my belts. I've got my book "101 Things..." and tools in hand. As my luck would have it, once everything is off, I count the shims. I only have five. 1, 2, 3, 4, 5..... Awrg!

The dealer replaced the belts for the PO about 2 years ago. They left one off for some unknown reason (there was a reason, right?).

Before I go give the same dealer even more profits in their parts dept. by buying another shim, can someone tell me I really need six, and that the 930 isn't different in this area too.

Thanks.

P.S. - At least my wife is happy. I had to clean my hands to get on the computer, and now I can cook dinner with her!

[GB83SC]

I just replaced my belt this weekend I have 5 in the center and one in the outer. I had ordered a new set with the belt just in case I was short. If you need one let me know and I will mail it to you at no cost. Take a flashlight and look at the bottom of the pully case someone might have droped one down there, dont ask!

[TimT]

it needs 6 shims.... you can run out of thread and have other issues with the fan.... and then again it may work forever......... a shim is like $1? just put it in

[Emission]

Originally posted by GB83SC
If you need one let me know and I will mail it to you at no cost. Take a flashlight and look at the bottom of the pully case someone might have droped one down there, dont ask!

Thanks for the offer. I think I will run to the dealer and get one tomorrow with no wait (I've got a Porsche picnic this weekend to attend).

[Early_S_Man]

I have seen it posted that later cars only need 5 shims. Assuming that you have the owner's manual, it should have a diagram/illustration with the correct number of total shims in it with instructions for changing the fan belt!

[Emission]

Originally posted by Early_S_Man
I have seen it posted that later cars only need 5 shims. Assuming that you have the owner's manual, it should have a diagram/illustration with the correct number of total shims in it with instructions for changing the fan belt!

Interesting idea, so I checked the manual:

"Correct belt tension is attained by changing the distance between the pulley halves. This is done by adding or removing spacers which are installed between the pulley halves; spare spacers are kept between the outer pulley half and the retaining nut."

It says nothing about how many are required for proper installation. The exploded view picture shows six, but then again it doesn't show my engine either.

I find it interesting how it refers to them as 'spares' when they are on the outside. I am willing to bet I can get by without the one.

[Doug E]

When I replaced my belt recently I found I only had 5 as well. I picked up a few from a local shop for 50 cents apiece and added one back for a total of six.

For the 50 cents (or even if it is a dollar) for one shim I'd do it just for the piece of mind.

[jkeyzer]

They are not really "spares" in that sense.

[Emission]

I just put everything back together with the 5 shims. Tomorrow, I will buy another shim so I have the 'correct' amount (it's all about peace of mind).

As far as I can tell, there is NOTHING that extra shim will do on the outside where the 'spare' shims go. The only mechanical difference is the nut gets a few more threads to bite when the shim is not there. It has nothing to do with anything else whatsoever.

[Jim Sims]

Without the proper number of shims the concave side of the cupped or dished washer (under the nut) can end up contacting the end of the alternator shaft before bearing properly on the edge of the stack of shims. I have seen a dished washer "flattened" and the fan pulley begin to loosen and wobble due to a lack of shims. You may indeed only require 5 shims but make real sure the dished washer is bearing on the shims and not on the end of the alternator shaft. An extra shim is inexpensive compared to the other potential costs if something goes wrong. Cheers, Jim

[Emission]

Originally posted by Jim Sims
Without the proper number of shims the concave side of the cupped or dished washer (under the nut) can end up contacting the end of the alternator shaft ...

On my '86, I don't have a 'cupped' washer (like I remember on my friend's '80 SC). That may be the difference.

Under my nut is a washer/piece of metal that is 'hollow' so it doesn't press on the alternator shaft. I will take pics when I adjust the tension in a couple days.

[Wayne 962]

WOW, So much WRONG information here. Too bad it's on one of the most important parts of the car!

You need the correct amount of shims. I have heard that some cars only came with five, but I fully recommend using the six on ALL 911s just to make sure.

If you don't put the extra shims on the outside, the nut may bottom out on the threads of the alternator shaft. This happened on my 914-6 engine (a long time ago - before I knew better), and led to it's overheating and subsequent destruction.

Do not listen to anyone who says that these are not necessary. Unless you know how this works, it's very easy to say "heck, I don't need them on the outside," and toss them in your glove box. In reality, this is the worst thing that you can do.

You can probably drive the car short distances with only five on there, but I certainly wouldn't trust it. Don't destroy your motor - do the right thing, and buy the $1 shim...

-Wayne

[Emission]

OK, OK, OK... I am buying the shim tomorrow!

I couldn't live with myself if a part .001" thick was missing and I needed a new engine!

I feel better with six shims anyway. Just think, if I ever drop one into the engine on a roadside belt change, I have a back-up!

[TimT]

Just do some imagineering.... there is really very little thread on the alternator shaft... the shims keep the nut in the meat of the thread. the fan stay in its own location just the pulley half is moved.... small changes in the distance between the pulley halves can increase the effective diameter of the pulley. This can increase alternator bearing loads, or lesser belt life.

quick tip.. find a gates catalog and find a "just smaller belt" with the same width and angles. Install it and adjust properly, and you just got a fan that spins at higher RPM...=more cooling

you can have all 6 shims on the nut side of the pulley

been doing this for years and miles

[pbs911]

I was one who went with the 5 shims after reading the wrong info. Ended up cracking the outer pully half. Now I have 6, but why not more than 6?

If the sole reason for the 6th shim is to prevent the alt nut from bottoming out on the threads of the alternator shaft, then why not 7, 8, or 9 shims? As long as the nut was properly secured on the shaft, it seems like an extra shim would provide a little extra cushion of safety.

[michaelw]

I lost a shim down by the pully while doing my valves last weekend. I can't find them on Pelican. Does anyone know where I can pickup one?

Thanks,
Michael
87 Targa

[Jim Sims]

I believe one would want the nut to be fully threaded on the alternator shaft and there is a minimum bend radius that belt should be subjected to. Too many shims might mean the nut isn't fully threaded on plus it would allow the use of too short a belt that bends too sharply for good life. Also the fan speed would rise if all the shims ended up between the pulley halves (using a shorter belt) and perhaps over load the belt as higher fan speeds require more horsepower . Six is enough. Cheers, Jim

[scottb]

Michael: Look at the 911 & Carrera Engine Support Components section of the Pelican site. Click on "Cool Fans" and scroll down. You'll find the shims. The part number is H-106-564-00. $1.10.

Good luck.

[michaelw]

Thanks for the help in locating the shims. Hopefully Wayne does Lay A Way till pay day.

Michael
87 Targa