The trucks been running a little hot for a week or so, not too bad, but hotter than it has been. I figured it was because the temp outside is warming up. It was around 60 or so. I had noticed that the overflow reservoir was getting fuller. I had checked it several times over the last week or so, and the coolant level kept getting higher. I was thinking air in the lines somewhere. Last weekend I had the cap off of the radiator, warmed it up, and noticed air bubbles coming up. The level in the overflow did go down after that. Then yesterday it almost overheated on me. Temp was about 74. The gauge went almost all the way too the top. It didn't totally overheat, but got really close. Even driving down the highway at speed didn't seem to have an effect on it. I take it too a shop, they put a new thermostat in it. It's still doing it. Had the radiator replaced last year, so it can't be that. I assume the shop did a pressure test on it to check for leaks. I'm at a loss as to what it could be. Any ideas?

I forgot it's a 2005 with the 4.7 in it. Also the thermostat that was in it was a 180 degree one. The one the shop put in is a 195 degree one.

 

Definitely not a thermostat problem if the 180 was functional and it was overheating. I would flush the radiator and make sure that there is no air pockets in the cooling system. Is your fan operating properly? Any issues with the belt or waster pump pulley/inner bearing?

 

Fan is working. I thought it was the thermostat because the fluid was backing up into the overflow. I also popped the cap on the radiator after it had sat awhile yesterday. There wasn't any fluid that could be seen in the radiator. I thought that the thermostat had stuck closed, backing the fluid up into the overflow. Don't know about the pulley. The fluid was changed last year when I had a new radiator put in.

 

Had same problem with my 05 Quad 4.7 had air in system .Would be ok couple weeks then start running hotter than normal. I would remove rad cap let it come up to temp and have bubbles like you have. top it off then everything good for while.makes no sense at all built lots of cars and trucks and never had this problem with air pockets in cooling system. Installed heavyduty trans cooler made big difference in keeping temp lower and more consistent. the average temp here is 80 deg and now temp are consistent at195deg no matter what

 

Just to update on my problem. I drove it for 3 days without a problem. The temp stayed at about the halfway mark most of the time. The needle would stay just below the halfway mark. If I turned it off and restarted it, the needle would get just above the halfway mark, then go back below it after 15 seconds or so.

Even though it didn't run as hot as it had been, that's still too hot to me. The thermostat that was in it was a 180 degree one, the one in it now is 195, which is oem. Could that be the reason why the gauge is reading hotter than I think it should?

 

Mine almost always runs just below the halfway mark thats pretty much the norm

 

A click under half is normal.

 

Didn't know that was the normal range. The previous thermostat was 180 degree, so the gauge was lower. I've never had a vehicle that read as hot as this one does. Every vehicle I've owned before this one the normal range was halfway between cold and the halfway point. Thanks for the info.