Thanks all
i have done the engine flush
now the heater works fine
the engine temperature now is acceptable
80C° during normal condition
85° durning load
87C° when AC on
auxilary fan works great
engine fan is always turning with engine

i also tested the new and the old thermostat with hot water
begin to open at 71° and fully opned at 90C°
so i dont have to buy another one

oil pressure now 1.5bar i know its better than 1 bar
but before this problem happen to me oil pressure was 2 bar
i think should live with this 1.5 bar until i fit OM602 Turbo oil cooler and filter housing

That oil pressure at hot idle is okay. What viscosity do you use for oil? Same as when you had 2 bar at hot idle?

i use W25-50 and i have done an oil change and after few hot weeks i noticed this problem

Update:
this day because of the hot temperature outside (41C°) oil pressure dropped to 1.3bar without using AC
now dont use AC because it needs recharging
so after repairing it the pressure would drope to maybe 1 bar
is that gonna hurt my engine ??

Yeah, oil pressure seems decent without an oil cooler.
My 190 2.5turbo (before when my oil cooler lines were looped with heater hose(yikes)),
When I'd pull off the interstate running 79mph and sitting at the red light, my oil pressure would float around under 1 bar.
Now that I've got a little an10 stack plate oil cooler, even when my spotty a/c system gets my coolant temp levels around 100C, it will maintain 1.3/6 ish bar even after ripping on the highway.
I changed the oil early since I figured it must have been "cooked" by the excess temps it saw during that time with no oil cooler

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate

i use 15/40 synthetic on my 190D, your oil might be to thick

Oil pressure at hot idle is still well above the factory min. for this engine. So I would not be especially concerned. Although there are perhaps a few things like renewing the rubbers on the filter stem if your car has them like the 123s do. . That hot oil pressure is also very dependent on engine idle speed remember.

In the old days if you ran an American built car engine wide open expected lifespan was less than single digit hours. Mercedes did a lot better in designing their oiling systems. You could probably run them wide open for days and days with no issue. Germany had the no speed limit autobaun and Mercedes had no desire to see their cars broken down alongside the road in high numbers perhaps.

Plus they were a builder of high demand aircraft engines so had learnt a lot about adequate oiling for durability a long time ago.

A 15w40 might help reduce temp a bit vs your 25w50. Where in the world are? Only place I've seen that viscosity used is Australia and the middle East.

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CENSORED due to not family friendly words