crazyhouse2011

I just got home from a 50 mile round trip, doing 70 mph at 3100 rpm for the last 20 minutes. I pulled into my drive way and felt my coolant hoses. The upper hose was very warm to the touch (but not burning me), and the lower hose was cold just like outside. I felt my way up the hose until i was close to the thermostat, and it was kinda warm there. The coolant gauge was reading a hair or two below halfway, so normal temp. But why is my lower radiator hose so cold when the upper one is hot?

I feel like it's a problem with my thermostat.

D16z6, 5 speed, 95 honda civic EX, etc etc.

crazyhouse2011

Also, i forgot to mention that the heat works just fine, and the coolant is full. The hoses to the heater core are hot as well.

tech8

If the lower radiator hose is cold, it means the thermostat did not open yet.

crazyhouse2011

It's below zero outside, so maybe the radiator is cooling the coolant really well? I was doing interstate driving after all, and my radiator fan does turn on in the summer...

Boss727

mine does that too. As long as it's not overheating of overcooling, don't worry about it.

Schister66

My car has been doing this a lot lately too...it barely warms up, even after my 25 mile commute each morning. Today with the heat on, it barely registered half of what it normally reads on the temp gauge, but the heat still kinda works... it was -14F this morning

Keep an eye on it. When it warms up, check again and see if its still acting up

crazyhouse2011

No my heat was blasting hot, no problems there, and my temp gauge read just below half. As soon as i pulled in the driveway i popped the hood to check so the hoses didn't have time to dissapate heat. The lower hose was cold, and when i squeezed it i could hear sloshing noises, so i know there's coolant in it.

ej1b18c1

Being below zero outside does play a role. It's being air cooled while the thermostat is not opening because the thermostat is not getting 180 degrees to do so. If concerned just get a new thermostat and gasket, even oem is around $30-40.

crazyhouse2011

I don't have AC so the airflow to the engine block is much greater, so maybe your right.

TomCat39

I wouldn't fret, the aluminum block and head are really good heat conductors, so when it's cold out, it runs cool, especially with the air flow of freeway driving. During winter, my rad fan never kicks on ever, thought it was broke until summer rolled around and I finally noticed the idle dip of it kicking on.

As long as your guage doesn't go high are stay forever low, you are fine.

My Honda Tech friend told me during winter it can take over 20 minutes to have the fans kick on when doing the cooolant bleed procedure.

Former User

This^

The thermostat doesn't fully open until the engine temperature reaches 194F. When the weather is very cold, the engine temperature may not rise quite this high, but will still be hot.