I just put in a new thermostat to get my 4.9 back to the factory operating temperature (195 deg), which did the trick. I have been watching the coolant temp (I have an Autometer gauge to get an actual value) and it's been running right around at idle once it's warmed up, but gets just a little over 200 when driving (it's been ~90 deg here recently). I've also been in the process of flushing the cooling system and have been getting some nasty looking stuff out with each flush (using the Prestone chemical flush). Is running around 200 normal with a 195 thermostat? Should I consider a radiator with a larger capacity? If so, any suggestions?

 

You don't state what year, but my 96 4.9 has to be one of the hardest vehicles to burp I've encountered. The culprit is the upper hose, which is the highest point in the cooling system. The only thing that worked for me was to raise the front end and vigorously squeeze the upper hose with both hands. Once it burped the temperature returned to normal. I used to tinker with BMWs & thought they were tough to burp, compared to this, they were also-rans.

 

Thanks for the quick response. I checked to see if the upper hose got hot after the engine got to operating temp. Would it still get hot if it had an air bubble in it?

Thanks again!

 

I'm of the opinion that a partial blockage could still occur. I got mine to flow a little, got some decent burps with the front wheels level with the rear, but it still ran higher temp than normal. Once I ran the front wheels up onto the 4 post lift, and squeezed the crap out of the upper hose, it returned to normal. I was unprepared for this much resistance. I understand quirky stuff like that on a foreign exotic, where function sometimes has to follow form, but on a Ford pickup!? This might not be your problem, I know I tent to shout it from the rooftops since I became aware. You may also have just knocked so much crap loose with your flush that you clogged the radiator. A back flush often cures that.