Alright I just looked into some more things with my M103's cooling system

for entire process I parked the car up on my driveway, nose at the top of the driveway.

I suspected that there was air in my system so the first thing I did this morning (car sat overnight), was undo the 14mm bolt on the cylinder head for the water strip. water immediately began gushing out so I plugged it back up, no air pockets there.

I removed the reservoir cap and let the car idle for about 15 minutes with the heater on max. temperatures eventually rose to about 85-90C after about 15 minutes, but didnt notice much "air" popping up to the reservoir tank.

I can tell the thermostat is working because the upper radiator hose didnt get hot until the temps rose to around 80C. After 15 minutes of idling with the cap off, the upper radiator hose was very hot.

now the weird part is, my coolant tank water is cold to the touch. its like nothing even circulated through my coolant tank? the lower radiator hose from the coolant tank to the bottom of the radiator was cold to touch, same with the overflow. but the hose from the thermostat to the radiator was hot (im guessing just from heat dissipation from the thermostat housing?).

my engine water temps are at 90C from idling for 15 mins with the cap off, is the water in the coolant tank supposed to be cold to touch after something like this? is there something blocking my water passages in my cooling system?

If your not overheating I wouldn't worry about it.

i'm just not used to my water temps running that high, nearing the 100C mark.

I guess my old thermostat was opening early due to old age, the water temps always sat at a constant 80C, never moved a mm when I drove for the 4 years ive owned the 190E.

now that I flushed out the system and replaced the thermostat, it runs hotter and has me worried.