I have replaced the thermostat (and gasket) and made sure the coolant is flowing. No collant leaks anywhere and the radiator and overflow are full. For some reason, the truck will never get to full operating temperature. Especially in winter time.

I have tested the fan clutch and it seems good (I thought it was bad a while ago, but I checked it wrong.) I have a new fan clutch waiting to swap in, but the old one works as it should.

What else can I check into?

-edit-
could be the temperature guage, but it almost never blows hot hot hot air. Shoot, the truck won't even blow air hot enough to get the fog off the windows in winter time. So I definitely don't think it's getting hot enough to heat the heater core.

 

Sounds like:

A) clog in your heater core
B) air pocket in your heater core.

How do you know it's not getting to full temp? Are you relying on the factory gauge or a good, aftermarket one?

 

What temperature thermostat are you using ?.

 

I believe it was an 80 degree thermostat.

I've been dealing with this problem since last summer. The temp gauge used to get to the halfway mark and stay there. Now it's barely 1/4 of the way up. Last summer I flushed the heater core pretty good on two separate occasions. Fist time I got a bit of stuff out, but not a lot. The second time I got almost nothing out. I flushed it one way with a good stream of water and then I reversed the flow and did this a few times over and over.

I think this summer I'll try one of those radiator flushes.

 

Did you burp the cooling system after you flushed it?

 

yup. Even parked it on a really steep grade in our parking garage as suggested on these forums.

 

[QUOTE=DupermanDave;51478528]I believe it was an 80 degree thermostat.

I hope that you mean that its a 180 degree thermostat ?. The stock thermostat should be in the 190 - 195 degree range. You said that your heater isn`t working that well, try back flushing the heater core and see if that helps. Ive also had the temp gauge sending unit go bad before and the gauge would read just above cold all the time, replaced the sending unit and the temp gauge worked after that.

 

Eh my truck does the same thing.
Try throwing some cardboard over the radiator. i did that, and the heater works like a champ.
That just tells me its a stuck thermostat tho

 

Get on down to the Myota Stealership and get a Thermostat, Part #90916-03070 dual stage, 30 bucks or so.

 

i have a 180 degree thermostat and it stays around the 1/4 mark. try feeling the heater hose where it goes into the heater coolant shutoff valve ,and the coolant return and see if you feel noticeable temperature difference. this could indicate a plugged heater core.

 

I tried that in winter time, but it didn't make a different at all. I think I'll give it a shot again now that it's summer.

Sorry, I meant 180 degrees. Didn't see the one get left off of that. If it was 80 degrees, that thing would be open all the time here :-)

When I flushed the radiator last summer I also did the heater core. More junk came out of that than the radiator, but still not a lot. I'm going to try a few radiator flushes and see if that changes anything and also replace the thermostat with a 190-195 degree stock replacement.