Hey fellas (and ladies?)

So most of you that are on here frequently know that I restored my '56 F500 with a 272. One thing I didn't do to the engine (regretfully) was take the thermostat off and replace it and inspect the entry to where the coolant enters the block. I know I know...no lectures please.

So the other day I'm just starting my ride and I'm watching the temp creep up...170...180...190 (normal) and then it keeps going...200...205. At that point I pulled over I let it cool down.

After an hour I start it back up and limp the old girl the 2 miles home. So today I took off the old thermostat for inspection. It's an old Dole DVN-23XH 195 degree. The most nasty, goopy, rusty crud came out too. But yet the coolant in my radiator is "Ghostbusters green."

First question: Is it safe to assume that my thermostat was stuck and wasn't opening at all? I'm just a little surprised because I've driven the truck more than 300 miles since I changed the coolant and the temp always stayed around 190.
*I know the thermostat isn't supposed to start opening until 195 degrees which I never hit anyway so technically it shouldn't have started opening at 190.
*Wouldn't the engine keep getting hotter without the thermostat opening? Is the air blowing off from the fan and the oil lubricating internals enough to keep an engine below 200? (I doubt it...)

Second question: What's the best way to flush the entire coolant system?

 

Yes your thermostat would have been opening before . Your gauge probably does not take its readings from the exact same flow as the thermostat and a few degrees difference to your gauge " that may also be covered in guk " is not surprising . You can check your thermostat put it in cold water on your stove and heat it then cool it again , but a new thermostat is cheaper than an engine . There are many different brand of flushes out there just follow the instructions . Good luck

 

There are pipe fittings on either side of the block, just above the oil pan, that you should remove. This isn't normally part of a flush but if the engine hasn't been opened in a while there will be a bunch of rust and scale built up. Usually have to jam an ice pick or screwdriver in there to get the flow going. Then watch out!

 

I can't see what your problem is from here but I'd like to offer up some points to consider, for everyone:

In the '60s and earlier not many people sprang for anti-freeze. (In the '70's it seemed like I spent half my life replacing customers' water pumps and radiators) Also, almost no vehicle had coolant recovery (a.k.a. degas/de-gas) systems/tanks. Add in the normal release of sand casting remnants in the cooling jackets and you have the trifecta of cooling system clogs. I've removed core plugs (a.k.a. freeze plugs)(not really freeze plugs but rather how the casting sand is emptied after casting is complete) and found what sometimes seems to be pounds of river mud. No chemical is going to remove that without mechanical help. It doesn't necessarily mean that the engine requires tear-down and boiling. Many times that crud can be removed with a flush gun (see:PowerClean® Cooling System Flush | Gates Corporation and/or google for other similar devices) that introduces both water and air (the air bubbles create voids in the stream that allow the water to 'slam' into and dislodge the crud.) Other times the core plugs will need to be removed and you just need to use some wire and picks, cussing, getting dirty and a steady stream of beer to dig out the water jackets from under the truck while occasionally rinsing out the fruits of your labor.