Coolant too cool.

ultraclyde said:

You live too far north. It's a Florida truck.

Always consider part geography.   for example, on the C4 i bought from pimpm3, the Florida battery worked great in FL, GA, SC, NC, TN, KY, and OH, but it does nothing but click here in MI.

This truck was originally titled in PA and was always titled in PA.  That's not to say it wasn't some weird dealer mixup and it's actually a southern package, but doubtful.

Ironically, the truck's history is that it was bought in 94 by retiring snowbirds.  I can see where the front hitch used to be mounted for towing behind (I assume) a motorhome.  The sagging headliner and sun-faded paint along with the complete absence of rust and low mileage support that story.

I suppose I'll try another stat but I don't have high hopes.  This morning in single-digit temps I started the truck about 10 minutes before I left.  The 15 minute drive to work was a steady supply of about 60 degree air out of the vents.  My poor dog thought it was the end of the world and looked at me like, "are we there yet?"

gearheadmb said:

Sounds like a design problem more than a malfunction problem. I would verofy temps with a scanner like stated above but everything you say about it being cool under the hood makes it sound like it is in fact not getting up to temp.

Back in the old days guys would put a piece of cardboard in front of half of the radiator to get the temps higher through the winter.

I don't buy the design problem theory.  An EFI vehicle in the 90s wouldn't have passed any emissions tests for sale at 120 degrees.  Catalyst warranty claims would have been through the roof, customer complaints about heaters not working, and other failures associated with running too cool would have been rampant.  So, yes, I agree.  Not getting up to temp, but I believe it to be a malfunction as opposed to a design flaw.

I will test resistance at the temp sender and compare with what the googles tells me it should read.  I don't have an OBD1 scanner, but the only thing the scanner would do is calculate the resistance into a temperature for me.  I already know that the engine feels cool and the gauge reads cool, I just need to check the resistance at the sender and hit it with an IR thermo to confirm exactly HOW cool.

If your replacing the thermostat, id  consider trying a OEM thermostat. The aftermarket may fit and have the same rating, but function may not be identical. 

Example: 2003 Subaru Forester after replacing  water pump, timing belts, and thermostat.  The thermostat was a Stant balanced flow with the factory temp rating. Around town the temp was good and held steady without a problem, but on the highway it would run hot if RPM was over a certain point (regardless of road speed). I could watch the gage and see when the thermostat opened, and then would close before temp dropped. Fluid levels, radiator, fans were all working properly. 

The culprit was the thermostat. The aftermarket thermostat had a much thinner spring and smaller body. 

The cooling system had a bypass hose that entered on the engine side of the thermostat, and the aftermarket thermostat would short cycle when the flow through the bypass was above a certain level limiting the flow of water from the engine.  New OEM thermostat solved the problem. 

In reply to No Time :

This IS an OEM stat.  Used the VIN and got it from the dealer because it was only $1 more than a Stant from Auto Zone.

For the last twennie years or so, I've tested my replacement thermostats in water on the stove. I've even got a specific pan so Mrs. rdcyclist doesn't have a coronary. Used to use a regular thermometer but now I've got a fancy insta-read thingy. Testing became key with the V6 Audi's I've been running 'cuz a bad one means disassembling the entire front of the engine to replace it. So I just do it with all of them. Out of about 20, I've had a single bad one. 5% is enough to take 10 minutes for testing.