So today I noticed a difference in behavior, not necessarily a problem (yet). I have the OEM 180* thermostat. I normally run 186-188 while driving around and when stopped and idling for long periods I would see it warm up to 194ish.

Today after driving home on the interstate (a little heavier than normal driving) I noticed that it warmed up to 199. It also warmed up a little quicker than I normally see (slowing down at stop signs and such). While driving at speed it would cool down normally. Only when forward movement slowed would it warm up.

I'm just trying to think what could be causing it to warm up with less airflow yet remain stable at driving speeds? Would it have something to do with the fan or clutch? I just replaced it about 1000mi ago when I did my HGs.

 

I would get a cooler thermostat before the weather warms up. Eliminate it as a problem.

 

He's already got the OEM 180 stat.
Robert, I think your a little paranoid. If you are having an "air flow" cooling issue, you will see your temps slowly climb at idle and they won't cool down until you drive. That's when you need to take some stuff apart, maybe hose off the exterior of the radiator and check your clutch fan. Also, If your clutch fan is weak, your engine will heat up on hill climbs and the fan wont keep up. Honestly, I wouldn't do anything unless you see 205+ temps.

 

I wouldn’t sweat it unless you see 210F. I’ve had both my 99 & 02 spike up to 212F in the middle of the summer at idle with the AC on. As long as it cools down on the road it’s just the ambient temps and idle without air causing the temp to climb. 212F is my absolute max! With the OEM 195F these engines were in the 210-220 range for years.

 

 

I second check your fan clutch. It only takes a few seconds and will give you piece of mind.

 

 

Here is a basic one, but if you google fan clutch test you will find lots.


https://www.2carpros.com/articles/fan-clutch-symptoms

 

A small amount of air may be in the system. Let it sit overnight, remove the bleed screw and use a small funnel to add coolant through the bleed hole. It's a good idea to do this occasionally and any easy way to keep your system as air free as possible. Even if it doesn't help in your situation you're eliminating a possible cause.
......

 

My system is air free, new radiator, new oem hoses, new oem Genuine 180 stat, new HD fan clutch and fan blade, etc. I run 190-195 all day long. At stop lights or idle after driving, 203-208. As soon as I start driving, it drops to 194-195. Don't sweat it. As long as you are under 210, you are fine. I would only be concerned if the temps were high while driving.