Temp reads high while moving, but cools while stopped?

[AlbatrossCafe]

I recently re-routed some coolant lines on my L28ET. On the passenger side of the engine, I removed a 3-way bypass valve and 3-way fitting out of the rear of the engine and replaced it with a 2-way valve at the rear of the engine. I have seen other engines like this and read it would be OK as long as I don't go crazy while the engine is still cold.

 

Problem: After the engine is warm, the Temp gauge sits PEGGED at 250 degrees while driving. I was initially very concerned, but what I noticed is that while idling, it goes back down to it's normal operating range of 180 degrees! As I move, it climbs again (fairly rapidly). My gauge was working fine before I re-routed my coolant hoses. Also, my heater works so I know coolant is flowing through there.

 

Where is this temp gauge? Is it absorbing hot hair from somewhere else? Any ideas why this might be happening?

 

Here is how I re-routed my lines.

 

From this:

 

 

To this:

 

Edited September 17, 2018 by AlbatrossCafe

[Chickenman]

You may have an Air Lock. Bring the system up to operating temp, with the Radiator cap removed. Watch the fluid level. It should drop as soon as the thermostat opens. 

 

Then add coolant. Rev the engine to about 2,000 - 2,500 RPM. Coolant level should drop some more. Add coolant till filler neck while maintaining elevated RPM. Then slap rad cap on. This will fill radiator completely. Of course you are running the factory Coolant recovery tank? 

 

 

[AlbatrossCafe]

4 minutes ago, Chickenman said:

You may have an Air Lock. Bring the system up to operating temp, with the Radiator cap removed. Watch the fluid level. It should drop as soon as the thermostat opens. 

 

Then add coolant. Rev the engine to about 2,000 - 2,500 RPM. Coolant level should drop some more. Add coolant till filler neck while maintaining elevated RPM. Then slap rad cap on. This will fill radiator completely. Of course you are running the factory Coolant recovery tank? 

 

 

 

Yes, I am running that tank. The coolant level is about 1/2" above the "Min" line.

 

Ah of course, it seems obvious now that you mention it. I filled the radiator to the brim once and called it good. I did not run it for a bit and then add a little more as I normally do. When I opened the rad after pulling over on my way home, the coolant was decently below filler neck.

 

I'll add more this week and report back. Thanks.