I'm getting close to 200k miles on my 1993 325i and have never changed out the tensioners on the belts. They look/sound OK. Should these be replaced? I hate to fix something that is not broken. However if one freezes up, I'm stuck.
if there is 200k and they are the original belts I would have them replaced. They are relatively inexpensive and easy to replace. Check the surface that contacts the pulleys for cracking/decaying. If they do have cracking then they should be replaced.
I think he we referring to the pulleys that keep the belt tight. As mentioned here check the pulleys for wear, cracks, etc. You can also feel how much tension they are placing on the belts, by releasing them like you would when changing a belt. At this mileage, I would probably just replace them, especially if you are going to driving this car for a while. They are not that expensive and you can do it yourself. Bavarian Autosport sells them. Why breakdown if you can prevent it. A stitch in time saves nine!
Take the tension off the belts and check the bearings for play. If there is an appreciable amount, replacing them is not a bad idea. You may not be able to hear them without a stethescope, but if you listen to them you should be able to tell if the bearings are toast. If they fail, it will take aout the serp belt and leave you stranded.
Replace them now. Murphy's law says that they will fail at the worst possible time like in a rainstorm at highway speeds. My wife was driving and never heard the noise it must have made because it was raining hard. She severely overheated the engine and it could have been prevented if I had proactively replaced both the idler and tensioner pulleys. My 525iT had about 165K miles when the tensioner pulley failed.
