[SLK350]

Was travelling along the freeway doing around 120 km/h when out of nowhere it starts screaming at me and I notice that the temp is around 120* C.
It was fine the rest of a while in traffic going no more than 50 km/h but the second I start staying steady at 65 or above, it starts to rise. Heater is NOT heating. Is it the thermostat? Something else? Thanks in advance.

 

[SLK350]

Not sure if it's been done. I'm probably gonna go check the belt to the pump soon. It's just shy of 200,000kms

 

[SLK350]

Are there any DIY's on this? I'm not very mechanically inclined, but I'm good with instructions and I would love to save the cash.