A hose in the engine is frosting up (like you may see in a fridge - see image - the hose/pipe is not normally white!).

Any ideas what this may mean?

I've also losing some coolant in the radiation (..but that maybe unrelated?).

hose frosting?

3 Answers 3


That is totally normal. It's the AC line from the orifice valve to the evaporator (inside the cabin) which is supposed to be cold. It's common for these to frost up in humid conditions.


This is a good thing and shows that your AC is working properly. The line you are looking at is the cold side of the system, between the condenser and the Expansion Valve and the Evaporator Core.

This frost is caused by the Expansion Valve, which reduces the pressure of the freon in a liquid state, therefore dropping the temperature before the freon reaches the Evaporator Core. The Evaporator Core is housed in the Heater Box Assembly behind the dash where the Blowermotor pulls ambient air through the Evaporator Core, exchanges heat with the cold freon, and blows out your vents.

This means your AC is probably blowing ice cold.


get your car ac expansion-valve checked by a qualified mechanic. if you had never seen that earlier in your car, get it checked for proper refrigerant pressure at both high and low sides.

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