Radiator Pressure, need new Thermostat??

[KalCas3]

I noticed my fourth gen, 2008 Toyota 4Runner V6. The engine oil cap have some milk chocolate, my first thing thought that I might have head gasket leaking but I followed the symptoms tests, it went back normal when the engine is hot. Eventually when engine is cold the radiator hoses, upper and lower have too high pressure, hard to squeeze them so I loose the radiator cap just one opening air, it sprayed like a water gun! But when the engine is hot, all normal I am able to open radiator cap without spraying like a water gun... The hoses, upper and lower is completely different, upper is too hot, and lower is too cool.. So I'm suspecting Thermostat need new?? Please let me know as your best knowledge and experiences.

 

[<<<<]

Moisture tends to build up in fill cap. Over time it'll look something like you describe. No worries it's a 4th gen thing unless you have other evidence of head gasket being compromised.

 

[rdruss]

Not sure I understand relationship of milk chocolate on oil cap to needing a new coolant thermostat?
However,the upper rad hose should be good and hot, it's the water exiting the engine to the radiator to be cooled, the lower hose is the cooled water coming back into engine, so should definitely be a temp difference.

 

[KalCas3]

I believe I need to check the thermostat because upper hose is too hot, lower hose is too cool, not even hot, so big difference.