Running Too Cool

[HarleyJack17]

Sorry it is a Chebby but at least it isn't a three 5ichy.

Question: Has anyone every had a vehicle run to cold, will not come to operating temp and it was not thermostat related?  If so, what was the issue?

Basis:
1983 C-10 with 250 I-6.  Replaced T-stat, worked for a while, issue resurfaced, replaced T-stat again, no change.  It is possible that the these are bad units but of the 15 or so I have done over my life that would be the first.  I can even clamp the top hose mostly off and it does not help.  Gage is accurate and heat does not blow warm confirming it is not getting warm.
I am stumped unless it is a head gasket...but nothing leads me to believe the this, i.e. oil looks fine, coolant fine, no white smoke at all, purrs like a new born kitten.

Had all kinds of getting hot but never something that would stay cold. 

[Heo]

Put the T-Stat in a pot on the stove with
a thermometer and check at what temp
it starts opening. T-stats this days are junk

[machoneman]

Do the ends of the heads get warm? Careful, but when fully warmed the ends should be pretty darned warm. We used this technique on our old SBF Boss 302 dragster engines (no cooling system, block/head fill only, temp gauge was often inaccurate w/o circulating coolant). 

[HarleyJack17]

Two bad T-Stats in a row? It could be but that just strikes me as crazy that bad T-stats are even a thing these days? I will definitely check that since I will be going back into it for diagnosis I am sure.

The heads get warm but not hot. I checked with a IR thermometer and everything(on the cool side) was just under 130 degrees. Nothing go hot enough you couldn't hold/touch.

[Falcon67]

I would not be shocked, because of the quality of some current parts, that the t-stats are still not right.  As above, test it in boiling water with a candy thermometer.  180 or 195 should either work. 

[BigBlueIron]

Once and didn't realize it until after it was fixed.

Farm truck with an early powerstroke 7.3. Temp never came up much we assumed bad gauge or sensor or whatever because we really didn't care. New water pump and then acted like it should, same thermostat. It was used on the farm for every duty there was, running for parts, hauling way to big of loads of hay, hauling cows it got worked and that whole time it was running cold. It did run a little better after the pump and having a heater that worked was nice.

[HarleyJack17]

Did you ever find out why changing the pump worked? See that is odd, like this deal I have....normally they fail and overheat, not work better than designed!    I hope to get freed up and figure it out this coming week. Between planning a shop build, working on my Highboy, and helping a friend get setup to install a 5ton auto lift I am strung thin.

[FB]

the world of good thermostats is a small one, most are chi-com junk.
these are a little more expensive but its all i ever use now

https://www.summitracing.com/parts/emp-302/applications/make/ford

[Stangman]

A lot of the good thermostats when they fail they fail in the open position

[BigBlueIron]

Did you ever find out why changing the pump worked? See that is odd, like this deal I have....normally they fail and overheat, not work better than designed!    I hope to get freed up and figure it out this coming week. Between planning a shop build, working on my Highboy, and helping a friend get setup to install a 5ton auto lift I am strung thin.

Nope, Didn't make any sense. The only reason I changed it was the design for the water neck on those is poor and they eventually start to seep and when you try to remove the bolts they snap off in the pump. But when removed it was obvious it needed replaced anyway, lot of wear on the impeller.