Hi Drago!
My 240D does the same thing. In the summer, when its really hot and I let it idle slow, the oil pressure drops enough that the timing chain tensioner loosens enough to make a clacking sound. I think that is what is happening on your car. I just run heavier oil in the summer, and idle a little higher (850-900 RPM). If you have an awfulmatic, try taking it out of gear at the stoplights.

You might try replacing the timing chain tensioner and make sure your engine has good oil pressure.
Cheers!
Chris

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1983 Turbocharged 240D
1982 Mazda RX-7
1974 Mazda Rotary Pickup Converted to an EV