How do I tighten my alternator belt?

[jbg]

Hello,

According to my records I replaced the alternator belt about 1 year ago because it was slipping (chirping) under ~1,500 RPM. Now I do not drive the car a lot, but I have noticed once again the belt is chirping. I can rotate the belt 90+ degrees in the middle of its longest pulley distance. I feel it needs to be tightened. Empirically, when doing a job like this, I am used to a threaded rod that the alternator can be adjusted on. This adjustable mount is fastened, or held in place, by another nut/bolt. The other day I could not determine if this was the case do to sticky oil near this end of the engine. (I have confirmed that said oil is not touching the belt nor its pulleys). I only have the D24(T) manual for engine repair, I do not have one that covers this seemingly trivial question.

Can anyone confirm my assumptions, or set me straight? Naturally a picture or diagram would be fantastic!

Thanks.

[piper109]

Sounds like a loose belt to me. Just tighten it. If you dont have a threaded rod to tighten with, loosen the adjusters, put a big screwdriver between the alternator and engine block and pry, then while the tension is on, snug up the adjuster screws. I doubt you need to loosen the pivot bolts as the prying will overcome them. It sounds a bit agricultural but its all thats needed. If you can play music on the tightened belt, its too tight so slacken it a tad.

Steve

[v8volvo]

The alt belt on these does tend to loosen up if recently replaced. I usually have to re-tighten about 1000 miles later. It is tough to get enough tension on the belt, and it needs to be quite tight. Steve is right, you do not need to touch the upper bolt at the pivot -- the alt will rotate on its rubber bushings without loosening it. Unfortunately on these engines there is no threaded rod for making adjustments of belt tension, so this job requires some delicate use of brute force with a long lever. In addition, there are some tips that will help keep it tight this time. The most effective method I have found for tightening, which I have adopted from Tom Bryant's method, is as follows:

1. Loosen lower adjustment nut, and also loosen bolt that attaches adjustment strap to front of engine; slacken alternator belt and replace with new if belt is worn.

2. Underneath the car, using a long square-section prybar, crowbar, etc (anything that is long enough and has at least one flat side on it so that it does not jump out of position), pry the alternator away from the engine by levering between the alt case and the squarish chunk of cast iron that protrudes from the engine block immediately adjacent to the alternator. Do not pry against the aluminum oil pump housing on the very front of the engine; you risk breaking the pump housing casting or disturbing its gasket. Be careful to keep your prying instrument against the iron of the engine block. The squared-off protrusion mentioned above will be obvious when looking up from below. Get the belt good and tight, then tighten the adjustment strap nut, but *not* the bolt that secures the strap to the engine.

3. Release your pressure on the prybar, so that the alt mountings come under tension. NOW, tighten the bolt that attaches the alt adjustment strap to the engine. (This same bolt is one of the oil pump bolts -- don't make it too tight as you will squish the paper oil pump gasket and cause a leak that will take big repairs to fix -- just tight enough to do its job!)

4. Leaving the bolt securing the adjustment strap to the engine tight, again loosen the adjustment *nut* (attaching alt to strap), and using your prybar, again set belt tension. Tighten nut and release the prybar, and you're done.

As compared with simply loosening both fasteners, tensioning belt, and then tightening both fasteners and calling the job done, this method eliminates the possibility that the adjustment strap might not be hard up against the threads of the attachment bolt going into the front of the motor, allowing some settling of the adjustment and resultant loosening of the belt. This procedure uses belt tension to take the slack out of the interface between the strap and the mounting bolt at the engine, ensuring that your final adjustment will not slip over time. Should help your belt stay tight.

I had one car that was going through alt belts because it had sat for a long time and the alt and crank pulleys had rusted. The rust acted like sandpaper on the belt, wearing it away until it got loose and began to slip. I wore out 2 belts that way, but the third has lasted now that the rust is gone.

[jbg]

Thank you for the replies piper109 and v8volvo,

I was able to sufficiently tighten the alternator belt and I feel it will hold its tension better than before. That small square portion of the engine block is a perfect place for a lever, I'm surprised I've never noticed it before.