New owner/ 240D temp issue after t-stat change

[keram69]

Hi, guys need some help. I just got this MINT condition 83 240D with only 60K on it. The temperature seemed always high to me, so I ordered BEHR t-Stat and temp sender from AutohouseAZ. Tested the new T-stat in hot water it opened at 81'C. Friend put it in for me.. And my dilema started.
now .. when I drive on hwy the car runs on 100'C mark (on gauge) when I stop and use my IR thermometer it reads 90-92'C by the area of the sender on block engine.
So, I need suggestions guys. Do I drain by the block engine and re-fill it..
Do I have air lock ? I tried few tricks from this forum already, I put the car on ramps ( nose up ) and run the heater etc. no go same outcome.
- I am using correct OEM coolant (Mercedes )
- I am using correct radiator cap 1.2bar (Mercedes) should it be 1.4bar ?
Is the hash mark on gauge after 80'C ... 100'C ?

Thanks[IMG]file:///Users/Keram/Desktop/IMG_0152.jpg[/IMG]