Have you tried a complete flush of the system and refilling with new a/f? I would at least test the a/f to see if it needs to be replaced. Just a thought...

 

By posting that the truck only got to 120-140 in -24F I figured you would get I don't have heat in the cab. My bad, military taught me assume nothing

For better info: the engine does not come up to temp and there is no heat in the cab (Tells me there is nothing wrong with the sending unit or gauge)

If the engine came up to temp and there was no heat in the cab would indicate a plugged heater core (not the case)

My dad installed two different new aftermarket thermostats and I installed a new OEM (same results)

Water pump moves water, if it failed you would get a overtemp (not the problem)

If the engine came up to heat then I would look at the blend door

Fluid has resently been replaced

 

When the motor is cold, as in before you start it, does the fan clutch spin freely or is it locked up or very hard to turn? And have the rad. cap checked or replace it. If it's not building pressure in the system it will lower the boiling point. And the -24 is still a big factor, as these trucks have good flow and some times do struggle to get up to temp. Which is why some people use the cardboard.

 

What is the temp on the new t-stat? I put in a 180* a while back and in 40* weather I cant get the truck up to 140* and the heater will only blow 90* which feels mort like 80* when the cab is cold. I would give the cardboard a shot or change the t-stat to a higher temp range.

 

He says he put in an OEM from dodge, so I assumed they sold him a 195.But dnfd is right if you a installed a 180.

 

Do these trucks have an electronic engine temp sensor? I know that some are controlled mechanically and electronically via a sensor usually located in the cylinder head. That could be a source of trouble if these trucks have one...

 

He's getting no heat , so it's not the sensor or the gauge.

 

It sounds to me like something is causing the t-stat to stay open and it's not letting the engine build enough heat. That's why I was asking about the electronic temp sensor. When an engine has one, the t-stat can either be opened manually (by the fluid heat level) or by the electronic sensor. If it is sending a bad signal, it can cause the t-stat to stay open constantly regardless of the fluid heat level. But, I still don't know if these engines have those or not...

 

Only if it was an electronic thermostat. The thermostat works completely independent of any thing else. It either works or it doesn't. It's simple, it's stays closed until it reaches the specified temp. Unless it is stuck open, has a big hole in it,installed upside down or if the temp is -24 lets say, it's gonna struggle to get up to temp with out blocking the cooling flow.

 

If The T-stat were upside down, the engine would overheat, not underheat.

When the Viscious Fan Clutch fails, it locks and blows hard at idle and at high speeds an will over-cool the engine. Carefully check under the hood, is the fan blowing like all get out while you're idling in the drive?

Our trucks don't have any type of electronic T-stat control. And there's no heat sensor in the cylinders that I am aware of.

Does the Truck in question have the Auxilliary Tow Package from the factory? That package came with a Larger Radiator core, and at temps of -24F you might very well need to cover a bit of the rad to get it to heat correctly.