Are the upper and lower coolant hose same with regards in temperature? If not, which is hotter?

 

The hottest is the the upper - the "T" hose as thats the output from the engine. if the thermostat is closed then the water will flow through the radiator and then be at its coolest point, before entering the water pump and going back into the engine

If the thermostat is open (under ~180f) then the radiator circuit is skipped and feeds directly back to the water pump until operating temp is reached.

 

 

That's actually backwards. When temperature is cold, thermostat is closed and radiator is bypassed back to water pump to heat the engine to normal temp. Once at normal temp thermostat opens to allow flow through radiator to keep temperature from getting too hot. Top hose hot, from engine to radiator or bypass. Bottom hose from radiator to engine is cooler.

 

Thanks Jeff,
I got all the stuff needed but: If I had to add a temperature switch to operate an auxilary fan which is 185 degress to turn on, I had to use it in the lower hose, right? Since, if I use it on the hotter upper hose, the truck will take more time to reach its operating temperature, is that right?
Gerry

 

I would wire the switch into the left hand hose of the upper T (goes to thermostat). I have an adapter there myself for monitoring coolant temp, and that is the straightest and best place to put it. If you put it in the bottom hose, the temp reading would be quite a bit lower than what the engine coolant temp sensor would be seeing.

 

A fan temp switch goes in the lower hose to moniter exit temp from the radiator. If the exit temp is high the fan kicks on to help the cooling fins of the radiator.

An auxiliary temperature gauge in the cabin should be wired to a sender in the upper radiator hose, preferably on the engine or radiator side of the tee, where the normal (hottest) flow of coolant goes. When the thermostat opens, flow through the bypass is reduced and can give a slightly lower, false reading of actual temperature . When the thermostat is closed, the water pump sucks all flow through the bypass. When open 73% of the flow goes through the radiator and 27% via the bypass. The percentages are as I recall, if not exact, then close.

 

^ He's right

 

does anybody know accurately what the water temp on the lower hose should be when the thermostat is open and engine up to temp?

my lower radiator hose never feels hotter than maybe 100 degrees when my coolant temps are between 183-198. The upper hoses at this temp are nearly to hot to keep you hand on but the lower hose is barely warmer than skin temp.

i know on a conventional cooling system (aka one upper hose and one lower with a manifold mounted thermostat) the lower hose gets very hot, probably within 30 degrees of the upper hose.