Q – On my 1987 944S I recently replaced my alternator. After a few miles, my belt began to squeal on start up. I expected that the belt would need to be re-adjusted and I did so. After a few thousand miles the belt started squealing again. This time when I went to adjust the belt and the adjuster strut (turnbuckle) that has eye screws on either end had broken even though I was very careful not to over tighten it. At $63.00 for a new part I don’t want to have the problem again. What happened? Eric
A – There are three causes that I am aware of. I will assume you are not a gorilla and properly tightened the turnbuckle securing bolts and lock nuts. Over-torque will break them every time since the thread root diameter of the eye screw is only 9 mm. So that leaves the other two.
When you loosen the alternator mounting bolts and the turnbuckle to make the adjustment, be sure that you tighten them back up. There is a “whole lotta shakin goin’ on”! I am guessing that you knew this as well and that you did tighten the bracket bolts back up.
That leaves cause number three: It felt tight but it wasn’t.
The aluminum alternator mounting bracket holds the alternator at two points, one is fixed and the other has a steel “split sleeve” that it is a tight fit into the bracket when it is new. The sleeve is split so it can move when you torque the mounting bolt down. Doing so creates a “sandwich” made up of aluminum mount, alternator, split sleeve and the bolt that squeezes it all together. After a few years corrosion sets in and that sleeve seizes up. So when you think you have the bracket bolts tight enough there may be a gap between the alternator and the bracket. If you do not get the sleeve freed up, with the alternator moving on the loose bracket, your new turnbuckle will break just like the old one.
The fix is to get the sleeve free again. I usually heat the bracket first to loosen the fit. Since the sleeve is steel and the bracket aluminum it does not take much heat to break the rust bond. Then I use a long bolt and two sockets, (one the size of the sleeve and one larger than the sleeve), to push the sleeve back out of the bracket. Once it is out you can media blast the sleeve, sand the hole in the bracket, and reinstall the sleeve with anti-seize compound. The alternator is also easier to install with the sleeve pushed back out of the way. As you tighten the bolt you will notice the sleeve moving toward the alternator. When you apply proper torque to the mounting bracket bolt you will be getting an accurate measurement and the turnbuckle will no longer fail. The other issue worth noting is the condition of the bolt, threads, and the nut. I always install a new locking nut on the mounting bolts as insurance. If you are tracking your car Loctite™ on the threads would also be wise.
FYI: The air conditioning compressor on 944’s and 928’s are also secured with similar split sleeves. I have seen cars with compressors falling off the brackets for the same reason. If you are not sure if the bracket has a steel sleeve, use a magnet to check. It will save a lot of grief and a bit of money too if you take the time to get the sleeves back to like new function. MC