Thermostat???
 

Well it got to 38 last night here in Baton Rouge. The heat in my truck has decided to work un-evenly. Took a long time to get warm then when it did get warm-ish. The temp would go from cool to warm-ish, sometime this happened when I would sit in traffic, get cool. Then after about 15 miles it finally stayed warm. Any idea's? 98 Chevy, car hauler...

air bubble in the coolant system? hot and cool air cycling back and forth to me sounds like an air bubble.

add coolant to the system its probably low

+1 for checking the coolant level, then carefully look around the intake manifold area for coolant leaks. One ususally will see the leak running down the back of the motor and it will leave stains on the transmission housing. You may also see leaks running down the front of the motor near the water pump. If the leak is big enough, you may also see the coolant puddling right in the valley between the intake manifold, and the cylinder heads .
Good luck

there is a valve that lets the heated coolant move into the heater core. on my 96 chevy, i sometimes needed to beat that thing to get the water moving.

what were the truck's operating temps looking like? "long time to get warm..." you talking about the truck temps or the heater temps?

my money is on that valve.

FYI, is your coolant red? my dealership told me that coolant sometimes gelled up, and would clog the heater core. my truck would sometimes sound like a coffee maker. it would gurgle behind the dash, or sound like a cascading fountain. i flushed my heater core and it heated up much faster, and the sounds were diminished.

I'm with vash as I have the same series truck. That valve is operated by a servo which could be out of whack. Find the valve and monitor it's function. You might have to put a cable in.

Thanks for the replys
. Truck temps, motor, runs very cool. Even in the heat of the summer with AC on my temp gauge will be at about 30% of full scale. Never runs hot.

About this valve, where is it located? I will checl coolant level, but , if the coolant is low wouldn't it run warm?

the valve on my truck was on the firewall, near the inlet/outlet of the heater core. looked like a UFO.

You may not have a t-stat in the intake manifold and if not, your truck will run cool with a low level of coolant.
.LOL, I just spit hashbrowns on the keyboard.

here's the UFO:

[IMG]http://info.********.com/getimage/getimage.php?imagekey=815526&imageurl=http%3A//info.********.com/FourSeasons/74781.jpg[/IMG]

http://www.********.com/catalog/x,carcode,1303401,parttype,6860

Engine never warms up? Thermostat stuck open, GM DexCool gunked up?

Engine warms up OK. May have been "stuff" creating a blockage at of in the UFO. Have a had a few days where I have needed heat. Seems to be working better each day.
I am getting tired of cool weather aleready!! Give me the heat.

Don't give me heat with your humidity, but don't give me that wet, damp cold either. BTDT and scampered back to CA.