So I have had this car for about 2 months, and during this 2 months it has been cold outside(don,t know if this will help you all decypher my problem). The car is a 91 civic si with an hmotors single cam zc swap in it. About 45000-50000 miles on motor and components. Well here is the thing. I can drive my car for however long i want to and the upper radiator hose will be hot, but the lower radiator hose will be cold. When I meen cold I meen like i just pulled it out of the refrigorator(LOL). I have never seen the fan come on. The radiator is about 2 months old also. Well i thought it was the t-stat so i replaced it and BAM, the lower radiator hose is still cold. My car is not overheating and I have bled the system correctly also. People keep telling me that it is because it is cold outside and the radiator is just doing a damn good superb job of cooling the coolant. I can let my car sit in the drivewat for 35-45 minutes and the fan still wont turn on and will not overheat, and the lower radiator hose will still be cold. I don't understand whats up with it. Please let me know what you all think. Thanks H-T.

 

who cares if the lower hose is cold?

what is the problem?

if the car is not overheating and you are getting heat from the heater you are fine, nothing to worry about.

 

So, whats the problem?

 

That's the way my CRX HF is. I can let it sit in the driveway for 30 mins before I have to leave before work and fan doesnt come on or anything but my hoses are both warmish not one hot and one cold like yours. However the lower radiator hose should be just as warm as the upper hose though..Water pump maybe starting to fail? But as they said you really dont have any issues until the car does try and overheat on you.

 

Well I never had a car that the lower radiator hose stayed cold. Well I guess I will just drive it and see what comes along down the road. Thank H-T.