high water temp at idle / low rpm ???

[ACII]

Hy all

i am still fighting with my cooling setup..... right now i have flushed my cooling system and put in the right cooling fluid.

I also checked the T-Stat (180 version) .....and modified it with a small metall piece to open a little bit earlier.

Today i made the first test ride...
it is pretty strange ...
at idle rpm the temp goes up pretty quick over 235 degrees....
But when i rise up the rpm to around 2000 rpm or even more (the car is still in parking) the temp goes down pretty quick to the 195 degress

During driving i do have the same effect...at high rpm the temp goes down.

What do u think is the prob ??? Does the T-Stat not open correctly ? Or maybe the water pump does not work at low rpm ?

Before i did the flush ...everything was ok. But at the flush i recognized some metall abrasion....so maybe the water pump is dying ???

Hope u can help once again

Thanks
Achim