Engine not reaching operating temperature

[SnowDrifter]

Damn that's wild. Can't say I've ever seen the heater out pace the engines ability to produce heat

Glad it's sorted

 

[Matahoe]

engine should be warming up enough even with the fans on if the thermostat is the right temp and working properly

Ok, let's just say for the moment that you are right...and I still have a stuck open thermostat. Turning off the heater fans makes the coolant warm up quicker. So what is left to test? The coolant in the radiator? If it is still stuck open then I should be able to use a handheld laser thermometer and see if the radiator or hose is gradually getting warmer when the thermostat should be closed? That seems like a valid test.

 

[Matahoe]

Damn that's wild. Can't say I've ever seen the heater out pace the engines ability to produce heat

Glad it's sorted

With the heater fans blowing at high speed and the engine at idle I would not doubt it. Especially if you have good coolant flow (to and from) the heater cores.


Again, this is why I am flabbergasted at the lack of a better service manual procedure. Everything (other than removing and testing the thermostat) is left to speculation it seems. In other words...they don't give you any explanation as to what the proper operating characteristics are. For example: how should the engine coolant temperature look when given a certain outside temperature? How about coolant temperature vs rpm/ engine load or different driving scenarios?

 

[Doubeleive]

life experience of myself and probably several others tells me that the thermostat is the primary suspect, provided that you have not done any work to the cooling system previous to this occurring and it happened totally random. Its just not normal and given the thermostat is a mechanical hot/cold spring activated device that I have seen get jammed open, sometimes jammed open and stuck closed that would be the first thing to tackle there cheap and easy on these trucks.

 

[rjr]

I find that between 4-cylinder mode and an aluminum block, engine takes a long time to warm up. Some engines can lose so much heat through the block that engine can't warm up. Two examples were my 1950 Studebaker Commander 245ci 6, and I under stand the old Chrysler slant 6.
To test a thermostat without taking anything apart, let engine run until gauge stops rising. Touch radiator hose above thermostat. If it's cold, thermostat is good. If warm but temp is below where it should be, thermostat is not good.

 

[Matahoe]

The thermostat was replaced 2 years ago with ACDelco 15-11057 . This morning it only took 3 miles at 45mph to heat up with heater fans on.

 

[Doubeleive]

The thermostat was replaced 2 years ago with ACDelco 15-11057 . This morning it only took 3 miles at 45mph to heat up with heater fans on.

That would confirm that it is a sometimes sticky thermostat then.

 

[Matahoe]

That would confirm that it is a sometimes sticky thermostat then.

The only time it over-cools is when the vehicle is at idle and the heater fans are on.

 

[Doubeleive]

The only time it over-cools is when the vehicle is at idle and the heater fans are on.

Then it's stuck open a little, your temp should stay very solid, the only time it may fluctuate is if you were towing up a hill or driving at high altitude and pushing it hard. Some people may disagree but I've never seen a healthy cooling system budge from where it normally sits, maybe a hair or two if it was really really hot out

 

[Matahoe]

I am going to take some temp measurement at the hoses and see if the coolant is heating up in the radiator. Guess it won't hurt replacing the thermostat again. I just hate having to drain the coolant as there is no drain plug.