Series 60 Belt tensioner

You shouldn't remove the belt tensioner at all. What you need is the correct socket with a long Bar and then you stick it on the bolt on the front of the belt tensioner and as you pull it you should be able to take the belt off of the pulleys and install the new belt. Sometimes this requires two people to slip the belt on while the other one takes the tension off of the belt.

Once you release the belt tensioner it will have the required amount of pressure on it automatically.

 

Usually there’s a 1/2” square hole on the tensioner. Like already stated, no need to remove tensioner. Start over, put tensioner on, using a 1/2” Rachel or breaker bar, relieve the tension. It will only move one way. Route the belt properly, around everything except the alternator pulley, then, with your right hand relieve the tension with the ratchet/ bar installed in the 1/2” hole, and with your left hand slip belt onto alternator pulley.

 

That was very well explained. I replace serpentine belts on cars before but I've never done one on a commercial vehicle. I only knew that tensioners all work the same and once that happens bolt is tight enough it starts to move so that there is enough tension free to remove the belt. Sounds like you've had more experience than me with serpentine belts

 

My Freightliner throws them all the time, currently trying to fix the problem once and all. But, my first experience with a serpentine was a 1990 minivan. Looked simple enough, put the 1/2” drive on it, and snapped the tensioner in 2 !!! Once I took it off, you could see, they had 2 different 1/2” square holes. One extra one, in a weak point!!! What a dirty trick I said. Dealer only part !!! Very expensive do it yourself project. Lol They got Me!!

 

It sounds like your belt tensioner got damaged/weakened when you took off the belts. The belt tensioner is automatic and has its own tension built into it. As the tensioner gets old, the spring that provides tension weakens. Also, to my knowledge the belt tensioner cannot be adjusted once the belts are on, unless you repair the tensioner. You may also want to test the tension in your belts with a belt tension tester to ensure your belts are getting enough tension from the belt tensioner. However, it may be a pain to locate the required foot-lbs tension for your belts.