I recently replaced the alternator, which I have done before on other cars I have owned and did not think it would be an issue. I was able to get everything off and the new part on; however, the serpentine belt will not tighten. It has a lot of slack in it and I cannot figure out how to tighten it back to the way it was so it will run again.

Also, my when my truck was running I noticed that the temperature gauge was fluctuating between hot and cold. It would not over heat, but it would get hot and then get cool again. Is this the thermostat or maybe a head gasket about to go bad?

Any feedback would be much appreciated! Thanks!

 

A good place to start would be to replace the thermostat.
Either on the hood or on the front deck where the hood locking latch is located there should be a belt routing diagram. One of the pulleys has a spring loaded tensioner that you use to relieve the belt tension in order to remove the belt from a pulley.
It is possible that tensioner is frozen and not keeping the belt tight. Following the diagram, route the belt and with tension on the tensioner you can place the belt on the alt pulley. Some penetrating oil will usually help to unstick the tensioner if it is frozen and will not move when you try to move it with a wrench. If unable to get it to move you may need to replace the tensioner assy.

 

Thanks, Hanky. I am going to start with the thermostat. In reference to the slack in the serpentine belt, the tension pulley is working. Is it possible that the belt has just stretched and I am in need of a new one? The belt looks to be in good condition with no signs of cracking or wear and tear. Maybe I messed something by not using the tension pulley to remove the belt? When I took the alternator off I simply unscrewed it and disconnected the cables which naturally created slack allowing me to remove the alternator. Now, when I screw the alternator back in, I used the tension pulley to get the belt back on, but it is way too loose.

 

Did you find that belt routing diagram?

 

I did. Usually there is something whether it is a pulley or some sort of arm that allows you to loosen and tighten the tension of the belt. It seems that the tension pulley only allows you to create temporary slack. I feel silly because I have switched out alternators before on other vehicles and never had this problem. There is probably something really simple I am missing, I just can't seem to get it...

 

Yes , you are correct. You need to hold the tensioner against the spring tension while you reinstall the belt. I usually save the easiest pulley to get at for last to install the belt. Most times it is the alt pulley since it's right on top and small.

 

I got it! I knew I had to be missing something, and I kept looking at the diagram per your advice and realized I had the belt over a pulley when it should be under a pulley. I feel silly! thanks for your help!

 

Don't feel silly, guys who work on them every day have to check the diagrams because they are not all the same.