2017 Jetta 1.4 coolant loss

[raaizin]

My Daughter has a 2017 Jetta 1.4 who has a coolant loss. Car is at 118k miles, I changed the oil at 114k miles and coolant was at proper level. Yesterday the reservoir was almost empty with the red coolant light flashing. Mechanic pressure tested it and said there aren't any leaks. I pulled dipstick and oil is clean no signs of water.

How could it lose so much?

 

[shortyb]

A large loss like that, there HAS to be a leak. Most common is the water pump/thermostat housing. Link between the pump and oil cooler and end of cylinder head flange to heater core also leaks. Or any of the plethora of plastic joint pipes. Look around for telltale signs of dried coolant or that sweet smell when its running. Also, pressure check the reservoir cap or just get a new one.

 

[Trav]

It obviously has a leak. I would add a dye to the coolant and look for it at night with a UV light. The GM dye works perfectly with the VW coolant, a leak shows up as bright yellow and it is harmless to the cooling system. You will have to look carefully as some parts are under the intake low on the block.
If you don't see anything it is time to pull the plugs and looks down the cylinders through the plug holes with a articulating borescope so you can look up at the valves and head gasket mating joint. The light is good for all system dyes, coolant, a/c, oil, etc.

UV light

GM dye