Erratic cooling

Those air pockets can be hard to get rid of. But if you left vent on top tube open and cap off, ran it for a good while, probably no air. It should show up as a little extra pressure when removing cap, or cracking the vent, although it can get trapped, usually works it’s way to top.I think you need a new radiator,mines been doing the same thing for a few years. I flushed it with rust remover from harbor freight. Bought some time. If the side aren’t rusted out too bad, you can take them off and rod it out. Chances are the corrosion is right there at the ends of the fins.Will need new gaskets, or make your own.

 

Bad Air crompressor would put air into system,making it push coolant, which you stated isn’t happening.

 

Mine has been fine so far, once I’m running in 80+ weather, I’ll need the fan. 90+ and I’ll have to stop on long pulls and let it cool down, then proceed. Avoid letting it shutdown, while hot, Best if possible just get a new radiator. Before it gets too hot outside.

 

180 at the top and 144 at the bottom is a little too far spread for me. I like to see about 15 degrees difference. I would consider having the core rodded out if you have a good radiator shop to use. They usually can tell you by looking if they think its rotten and needs one before they start on it

 

Old rule of thumb on air heat exchangers is 15-40 degree drop. If less than 15, usually an air flow problem. If above 40 you have an internal restriction. I like to see same as @wore out, around 15-20 degree drop.

 

Something I noticed, is when the Jakes are on the temp drops quicker. I don’t enough to explain why. It’s besides the point really. Since their only on after topping a hill. But give it a try, see if you notice what I did.

 

Thanks everyone I need to wright some of that down. It takes very little air to cavitate a pump. It is also easy to over look as it may only happen when it is building pressure.

 

Builds no fire in the hole when the exhaust valve opens BTDC. My minds eye can see the but never noticed that.