Cold lower radiator hose?

I've got another coolant leak. This one appears to be the lower radiator hose leaking (I really hope it's not the radiator). Anyway, while trying to find the source of my leak I discovered that the lower hose is cold to the touch.

I had just driven about 30 miles. The engine was up to temp. Outside air temperature was about 35. The upper hose was hot, but the lower was cold. Is this indicative of a problem, or is this normal?

 

Thermostat is bad and stuck.

 

The bottom one should be colder to the touch but if it was up to temp it is should still be warm.

 

This is for 100% certain? I ask because I just got the truck back from the dealer for a frame replace and the assholes claim they changed the thermostat, and they charged me for it.

Edit: More info, because I really don't want it to be a problem. If it is I'll fix it, but I really don't want to. The temp gauge reads normal. Heater works fine.

 

This is 100% certain? It should be cooler but not cold. It was 'up to temp'? or getting hotter?

 

If the top hose is super hot and can barely touch it and bottom is stone cold then it’s definitely the thermostat. It’s just like hot air rises. Same concept. When the thermostat is stuck closed it allows minimul to no flow causing too hose to be hot and bottom to be cold.

 

I had just driven a little over 30 minutes. It was only 35 degrees out. Was it up to temp? The temp gauge said so - it was at a little over half way.

 

Wouldn't that lead to overheating? I just asked the dealer why they changed the thermostat. They claim the old one was stuck open. It's really amazing how many problems manifested themselves after I dropped that truck off and before I picked it up.

 

It's hard to gauge at 35 degrees. The 'jiggle valve' will let some water through.

30 minutes in 90 degree weather with a stuck closed thermostat would prob. most certainly have you overheating.

Over 1/2 way on mine is above normal. Was the bottom 'stone cold' or just 'cooler'? The radiator works 'in the top, out the bottom' so it should be cooler but should be 'warm'. Top is 'hot' 'til radiator cools it.

 

Alright, hard numbers. I think I might be looking for a problem where there is none.

I just drove for 45 minutes with a bluetooth OBDII scanner plugged in. Once it came up to temp the coolant got as high as 200 and as low as 194. It tended to return to 196. When I got home I zapped the upper and lower hoses with an infrared thermometer. Upper was 165, lower was 58. Air temp was 35.

Thoughts?

 

Sounds about right to me

 

I appreciate it. I'll see if I can find something else to worry about.

 

Yeah, seems all is well. Thermostat is barely opening just to keep engine at 195, hence the big diff. in hoses to engine.

 

Yeah your fine!

 

2nd this. Could be a bad fan clutch Imo. If it's 35F and you're cruising on the freeway or your fan is pulling too much air through the radiator, your bottom hose would feel pretty cold.

The diesels i work on have a common issue with the water pump impeller cracking (plastic) and spinning on the shaft (metal). You go for a road test. One hard accel and the temp gauge shows that you're overheating. You get back to the shop and the upper hose is scalding while the lower is room temp/ cold. I don't agree that its definitely the thermostat.

EDIT: Sorry, didn't read the whole thread and realize there was a conclusion. Just didn't want the OP running out to replace his TStat or yelling at the dealershit

 

Under the circumstances if that engine had a water pump as you mentioned I would have suggested that. But knowing that the 3.4 water pump in my opinion is a fairly stout pump and not normally the weak leak I wasn’t going to suggest a water pump.

 

Gotcha.

I wasn't suggesting the WP either. Apologies if that's the way it came across. I was just pointing out that multiple things can lead to a hot upper hose and cold lower.

 

I appreciate all y'alls help. You talked me back from the edge. All I've really got is a leak to address.

 

have you traced where the leak is coming from yet? My factory radiator had a pinhole in the upper corner behind the shroud.. the fan would throw a fine mist of coolant everywhere.. nasty white chalky looking when it dried... as the water level would drop down a few inches the leak would stop.. took me a while to trace it down. finally found it one night with a flashlight as the engine was cooling off..

 

Mine is coming from either the lower radiator hose or the radiator itself where the hose connects. I've got it stopped right now by moving the hose clamp right out to the edge of the hose.