80 300D(non turbo) Overheating?
 

MY brother is is Arkansas or I would drive over and check it out. However he is having a problem that sounded wierd to me and I'm looking for enlightenment.

He said that it started running warmer than normal and the alternator light is flickering on and off. When he looked under the hood he said that the alternator belt seemd to be moving slower than the pullies were rotating. Is this possible without the belt getting burned up? I didn't know if there is a mechanism that could allow this to happen in a Merceds. Any input would be appreciated.

Thanks,

Stephen

This sounds like he needs to adjust the alternator belt, which IIRC also drives the fan/water pump.
If it is not tight, the alternator will not be able to output full current, and at low output, may cause the CHG light to come on intermittently.
If it slips when the fan cluch operates, the fan will not cool the radiator AND the water pump would not spin fast enough to circulate the coolant properly, exacerbating the overheating problem.

If the belt shows any sign of wear/damage, replace the fanbelt at that time. It is much more comfortable to replace at home in the workshop than on the side of the freeway while taking the family on an outing.

Update and Ideas Needed!!
 

OK so my brother checked that belts and tighned everthing. No difference.

Then he got the bright idea to put some pressure on the alternator belt while it was idleing. The whole belt and pulley system stopped rotating while the engine kept right on running?????

Where is the missing link here?

Stephen

Sounds like the crankshaft pulley is loose or the dampener has come apart. Or the key was left out of the dampener.

lucforce may be onto something. Don't RUN it! If the pulley lets loose it could take out quite a few other things. Just pushing on the belt should not be enough to stop the belt and pulley from turning UNLESS the lower pulley is toast.