Hey i have an s5 fc with the temp gauge going up but when i touch the radiator and hoses they're still cold. It goes up slowly. Theres no coolant smell or smoke so i dont think it would be the coolant seals. But Im not sure what would make the temp gauge so up with the coolant and radiator still cold.

 

Thermostat could have failed shut, water pump could have failed, belt could have fallen off but that would be obvious.

 

As I understand it, the coolant gets pulled into the engine via the lower radiator hose via the water pump. When the engine block heats up the coolant past a certain temp the thermostat senses the heat and is supposed to open up to vent the hot coolant back to the radiator so it can be cooled down. It would appear your thermostat is stuck closed.

 

i was going to check the thermostat but the guy said he didnt put on in there. water pump is new. and belts are there

 

Figured it out. The guy caked the thermostat with lots of rtv and coolant wasn't going in