Noisy timing belt tensioner

[325e '87]

Ok, I have now replaced timing belts on two different cars and both of them have noisy tensioner bearings. One is conti, other is gates. The belts and accessories (alt, ac, ps) are all quiet and smooth and I verified the source of the noise with a stethoscope.

do I just have really bad luck? Anyone else?

[anonymoushero]

Had this happen not too long ago. I noticed a weird rattle at a certain rpm. Finally figured out it was the tensioner. Pulled it out and the bearing was shot. This was about a year and a half after putting it in. They can fail prematurely.

[richardodn]

What's your method for setting the tension?
I do this

1. Install everything leaving the tensioner free to rotate. I replace the spring itself when I do the water pump.
2. Rotate the engine clockwise to tension the top side.
3. Snug the set bolts on the tensioner

[Jeffnhiscars]

When you change the water pump and not the belt you can lose the spring altogether. What's the point of replacing it when the tensioner stays locked until the next belt change ?

[richardodn]

If all you do is the water pump, it's not needed. I follow the practice of water pump every other belt change, so I always do them together. As the spring sets the initial tension, you want it pretty accurate. It's a cheap part, so I do it for peace of mind that the tension is accurate.

[325e '87]

Thanks for the input Richard. I’ve decided to just go back in there and redo the tensioner install like you suggest.

i will say, I pulled the belt TIGHT between the Cam and oil pump sprockets, got that extra tooth in the belt. I wonder if I made it too tight. Probably not, but I’m opening her back up. The squeal is loud like a big supercharger sitting on top of the engine.

[digger]

excessive belt tension makes it sound like a supercharger, that is your problem.

[richardodn]

Once you have it on, rotating the belt and allowing the spring to set the tensions makes sure everything has settled in place. You want to do 2 full rotations of the engine back to TDC and double check that the gears are on the marks.

[325e '87]

You think I should get a new belt since I stretched the current one too tight by 1 tooth?

[richardodn]

It's good practice to replace the belt any time you release the tensioner.

[325e '87]

Thanks. Thanks for the clear suggestions and procedure.

[richardodn]

You're welcome.