Kenmore dryer's drum won't rotate

My dryer is a Kenmore model no. 110.96588210. It still works - but it exhibits the following problem:
After one drying session, I need to wait for it to cool down before I can restart it again.
This problem is very consistent: If the dryer is sufficiently cool, it will start and run till completion or till.. it gets too hot and then stop (before completing the session).
I did notice that starting it is not as easy as it used to be: It seems that the drum has a hard time rotating (mechanically speaking) - and the motor sounds some noise of trying to rotate something that is mechanically stuck. However, if it is cool enough, it will start after a 2-3 seconds.
I suspected the support rollers, but when I took the dryer apart, they looked all even (as if they are new). Each of them rotates freely on its shaft, and when the drum is mounted and rotating I verified that all of them rotate. So, does that rule out the rollers?
Also, if the rollers are gone, why is it temperature dependent?
I could have bought new rollers and see if they solve the problem, but it's a $50 expense which I would like to avoid if not necessary. It could turn out to be the motor (?) or some thermostat... How do I know which?
I did notice that one of the shafts (the rear right one) is worn out... could this be the problem? How can I measure the "freedom" of those support rollers rotation?
Thanks for any tip or idea you can offer! Sam
P.S. I searched repairclinic.com for possible tips or advice on my problem, but I couldn't find anything that addresses my particular case.
http://www.repairclinic.com/0100_16.asp
http://www.repairclinic.com/0088_8_4.asp#Level1_4
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On Jul 30, 10:14 am, " snipped-for-privacy@yahoo.com"

Sounds like one of the overheat sensors is shutting it down. They are located in the ductwork that's under the drum -- and eventually channles the hot air outside. If lint has built up around the sensor, it'll shut down. By the same token, go outside and see if your dryer vent is clogged. That'll cause the machine to overheat as well.
HTH, Mark
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Mark, thanks - you are correct, of course, but the overheat sensors are the symptom, not the cause. They *should* shut the motor down, considering the amount of resistence it encounters. See my reply to David Martel.
Thank, Sam
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A dryer that starts only when cool, and maybe turns off during a cycle when the motor heats up...and maybe has a deep groaning sound when starting up...needs a new motor.
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Part number for motor is 279787. If you can't get the blower wheel off, you'll need to whack it off with a hammer and install a new one.
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In article
wrote:

Might be a worn out belt, have you checked that?
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Nick, thanks for your reply. Actually the belt is almost new (I replaced it about 9 months ago), so it is unlikely to be the source of the problem.
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Silence,
Rotate the drum by hand. Is it unusually hard to do? Disconnect the belt and rotate the drum by hand. Still hard, I'd suspect the rollers are dirty or worn out. If it rotates easier with the belt off I'd suspect the motor's bearings or the belt tensioner.
Dave M.
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Dave, thank you very much for your tip! By far, this is the most meaningful tip I received so far. I couldn't implement it right away, but I just finished checking what you said and it seems that it helped my verify that the problem is not with the motor, but rather the rollers.
The rollers are very clean because I cleaned them recently. Apparently that was not enough and although I can't visually notice what makes them need to be replaced, it seems that after 11 years it is definitely time for them to be replaced.
The interesting thing is: I couldn't notice much difference between the resistence to rotation with and without the belt. However, without the belt it was siginificantly easier to rotate the drum to the OPPOSITE direction of the normal (i.e. the one dictated by the motor when it's on).
I think that I am going now to order those rollers (unless you say otherwise).
Thanks! Sam
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