Torque and V-belt tension

I am a novice please don't laugh too much at my questions.

What does nm stand for as it relates to torque.

And how to you measure the torque such that tightening is to specification.

190E 2.6 1993
I replaced the v-belt and water pump at the same time and now the v-belt (although the tensioner is turned to the correct mark) seems to still be little loose. I'm not sure how tight it should be but compared to my other cars it seems a little loose. The belt also makes and an occassional high pitched noise like it may be skippping.

What is the normal running temperature in Celsius?
Mine is running at just above 80. but when idling with the AC on it is closer to 100C with the auxillary fan on.
Could this be related to the belt tension. Visual inspection reveals that the belt is tuning the pulley appropriately. (the water pump is aftermarket and not Mercedes benz).


Please help.

Thanks,


Aaron

[sixto]

Nm is Newton-meters, a metric (duh) measure of torque.

You set torque by using a torque wrench. Older kinds look like a long socket wrench with a dial or graduated scale near the handle. When the pointer indicates the desired torque value, stop turning. Newer kinds have a knob at the end of the handle that you use to set a specific value. When you get to the preset torque value, it clicks to let you know. These are the common types.

Torque wrenches are available from most places that sell tools, even some auto parts stores... in the US anyway. I don't know if most torque wrenches these days are calibrated in Nm as well as pounds-feet (lbft)... again, might be a US thing. These are precision devices. Treat them gently, don't drop them, don't use them on stubborn bolts, etc. In general, you probably get what you pay for.

If your tensioner is set properly and the belt is still loose, then you might have a worn tensioner. It could also be that you're not familiar with how tight a belt should feel. But if you say the belt squeals like it's loose, it's a good bet that you need a new tensioner.

Your temperature sounds normal so I wouldn't worry about it. MB temp gauge readings do vary during normal operation unlike other cars where the temp gauge gets to a set point and stays there. If you feel the need to worry, do you know if your fan clutch is working? I'm not really sure how to check without risking your fingers.

Regards,
Sixto
91 300SE