Lower radiator hose cold

[jb86]

Ran the car for quite a while
The lower hose stays ambient temp
The thermostat isn't opening
The temp gauge shows right in the middle
The radiator fan comes on
I used a Wahler (?) brand oem spec
Maybe air locked
I was thinking of drilling a 1/8" hole in the thermostat to purge air
I filled cooling system thru the upper hose into both the block and the radiator

[92EcoDiesel Jetta]

Did you check the new thermostat in hot water and watch it open? Rare, but new stats do fail out of the box. Is it possible the stat was installed backwards? Did you run it with the expansion tank cap open? Trapped air usually work itself out and you keep replenishing the coolant. One of the best way to fill the cooling system is to pull a vacuum till all hoses are completely collapsed. Then stick the hose that you had pre spliced into the cooling system with a ball valve and you stick the hose into a jug with the correct amount of coolant and open the valve and watch the coolant sucked completely into the system- with zero chance of trapped air.

[8v-of-fury]

If it didn't over heat on your "quite a while" run then the cooling system is more than likely working perfectly.

If the lower hose were the same temperature as the top hose what effectiveness would it be at cooling the motor? lol. Smack in the middle of the coolant gauge is 80c and right where it should be running. Also you have to take in the fact that the air passing through the radiator is very cool, and is probably taking more heat from the engine than is necessarily needed.

 

[rabbitman]

Ran the car for quite a while
The lower hose stays ambient temp
The thermostat isn't opening
The temp gauge shows right in the middle
The radiator fan comes on
I used a Wahler (?) brand oem spec
Maybe air locked
I was thinking of drilling a 1/8" hole in the thermostat to purge air
I filled cooling system thru the upper hose into both the block and the radiator

In that case your cooling system is working perfect!!!!!!

What year/model is it?

I'd say your fan temp switch is calling for the fan to run for no reason. A cold lower hose just means the radiator is cooling the water faster than the engine can heat it and if your t-stat opened wide it would run waaay too cold.

[jb86]

91 jetta
Started as Eco diesel 1V engine
I stripped the car down completely
Had all the body work done and painted indigo blue
everything is new inside and out
All mechanical - steering, brakes, struts
Everything on engine is new
Brand new 20yr old car
Engine completely machined - block and head
I started it a few times to test fuel system ect
And warmed it up to the straight up position on gauge
The A/C is currently deleted - no compressor which I will ad later
The plugs and sensors in the cooling system are all connected
But the ones that plug into the hard lines on the A/C system are not connected
So
The fan runs high speed
After the car warms up to about the straight up point the high speed fan kicks on
Might be super cooling the radiator - it was about 22F outside at the time
I will test thermostat tonight

[jb86]

After I test the thermostat
Should I just drill a 1/8" hole in it to avoid any issue with trapped air
I did some reading last night, some say that besides simplifying bleeding air out it also lessens the shock of cold water rushing in when the thermostat opens for the first time

[R.O.R-2.0]

After I test the thermostat
Should I just drill a 1/8" hole in it to avoid any issue with trapped air
I did some reading last night, some say that besides simplifying bleeding air out it also lessens the shock of cold water rushing in when the thermostat opens for the first time

drill as small of a hole in it as you have a drill bit for..

[8v-of-fury]

22F? A diesel will have a very hard time keeping the radiator warm in that cold of temperatures. I think you've got a perfect system.