Need help! Truck wont warm up ...

[05kingranch250]

Ok its a 05 250 6.0 94457 miles. Truck wouldnt wont warm up. Have had it plugged in never gets warm even running for 20 min.until I drive it for a good 20 minutes . Replaced the thermostat and degas cap with napa parts ... that was a month ago. Sporadically does the same thing . Today its about 30 degrees let truck warm up for about 15 minutes and was plugged in last night. Will not warm up .. doesnt seem like cooling system is building pressure... after going to work 12 miles finally came to temp... Shut the truck off checked under hood upper hose was firm and hot had pressure when I opened cap but coolant level did not change in bottle like it usualy would when cap is opened... The head gaskets and egr cooler have all been replaced. No coolant leaks never had add any.No puking out of the bottle truck runs and drives like new....! Used to be a mechanic and im STUMPED! Someone please help... are napa thermostats junk? Only about a month old..... Thanks guys!

[05kingranch250]

Oh have been pulling bobcat runs awesome temp never moves from the middle ....

[10secondC]

Sounds like you got a bad t-stat.

[05kingranch250]

This thing has got me baffled... which I can honestly say doesnt happen often.....

[virginiagent]

What is your coolant temp? It doesn't warm up? Do you mean that you don't have heat in the cab? Is the vacuum line still connected on the heater valve?

[10secondC]

How much coolant did you lose doing the T-Stat. An air pocket in the cooling system will give that symptom as well.

[05kingranch250]

Coolant temperature gauge barely moves until you drive the truck even . Has normal heat no change in that once she is finally hot... I lost about a gallon of coolant. If there was a airpocket wouldnt it work itself out in a month lol!? I donno this is going to drive me insane...

[10secondC]

Change the T-stat. It's the easiest cheapest thing to do and you won't know until you pull it out to inspect it anyway. And lets face it.....it hasn't been cold enough that the warm up should take long.

[southend]

This is silly, without a monitor, you have no clue what your truck is doing. That thing you call a temp guage, is an "idiot" guage. Get a monitor on that truck, and post some useful info, we can figure it out from there. Otherwise we're wasting electrons.

Sent from my phone that somebody didn't help me get.

[10secondC]

Originally Posted by southend

This is silly, without a monitor, you have no clue what your truck is doing. That thing you call a temp guage, is an "idiot" guage. Get a monitor on that truck, and post some useful info, we can figure it out from there. Otherwise we're wasting electrons.

Sent from my phone that somebody didn't help me get.

Pretty easy to tell it's not warming up if you have no heat and the gauge says it's cold too. Especially when it's been in the 30's with teens in the morning.