1st Gen R53 Cooper S Most liked posts in thread: Bouncing Tensioner?

First guess is shot tensioner...

the damper on it should supress these oscillations. Another thing to check would be that the other accessories are tight and spin as freely as they should.

Anyway, this is acting just like an out of balance wheel that has a shot damper. Bounces like crazy at certain speeds, not so much so at others.

Matt

 

My car almost always hesitates some after the first start of the day. Maybe my tensioner is going out too.

 

Agree with Dr O, take the belt off and make sure all pulleys spin freely. Uh, OK not all as the SC pulley will take some effort and of course the crank well, it won't move by hand.

If every pulley is OK then the tensioner damper needs to be replaced.

 

I think you can just replace the little shock absorber.

 

I have seen idler pulleys make really odd and aweful noises.
Best idea is to remove the belt and check all the pulleys for smoothness. You should be able to rotate all the engine accessories smoothly 360 degrees. Any binding or roughness will cause noise.
Take the belt off and run the car. Does the noise go away. put the belt on a spary some belt quiet or silicone spray. Maybe the belt also needs replaing. Check it for heat marks and glazing

 

If its consistent then maybe a tensioner. Should be a parts warranty if its not too old.

 

I'll definitely consider changing the tensioner when I go to put the 15% pulley on unless it goes out before then.

 

You can change the tensioner w/o having to jack up the engine. Just go thru the wheel liner or if you have smaller hands do it w/o removing the liner.

 

Good to know. Think I'll have it looked at next time its being worked on if it doesn't go out before then.

 

Was the old one shot?

if something is driving the oscillation, that could be what caused the damper to fail. So a new one may fix the problem for a while, but if the root cause is elsewhere, you'll be doing this again shortly....

Matt

 

Depending on how the belt looks you may want to change it too. btw do you have an aftermarket S/C pulley... I have seen quite a few wear out belts before 40,000km

 

The alternator should be smooth and free spinning, not jerky. I think you may have found the assignable cause.

The AC will not have the clutch engaged and so should be even more free spinning than the alternator.

 

As it is difficult to explain a free spinning feeling. If you have the time, swing by any auto parts store and check out any alternator. This way you can feel what it should be. Just in case you are unsure.............

Or you can just wait and feel your reman unit.