model a radiator

I recently replaced my coolant temp gauge. After running the tractor for at least 20 minutes , the gauge needle still hadent moved. When the A was shut off , i could hear the radiator bubbling away. Did i not wait long enough? also, after, I removed the temp bulb and the coolant that flowed out was cool.

That is normal, factory gauge is attached to the cool side of the system. Gurgling is normal with thermosiphon. Temp gauges were not standard on gasoline engines.

Ok thanks for the quick response. About how long should it take to register in the "run" field on the gauge

That's pretty typical, Josh.

Those motors don't run real hot anyway without a good load on them, and even 20 minutes of just tooling around won't warm them up enough to register on the gauge.

They don't make much heat and they've got a very efficient cooling system. If you were to hear an A working from a distance, you likely wouldn't hear the exhaust except maybe when the governor grabbed. What you would hear is the howl of the fan. It draws an awful lot of air over that radiator. I had to warm one of mine up after a rebuild so I could retorque the head, so I ran it without the grille on, and covered the radiator with a kitchen trash bag and drove it around to warm it up. Once it was warm I left it run, with the radiator uncovered while I tinkered with the carb for a little bit. Before shutting it down I checked the radiator. The top was warmer than you would want to rest your hand on. The lower part was cool as could be.

On my Super C, even with a thrermosat, I have to close the shutters to heat it up enough to move the gauge on a short run if she's not working hard.

And it will bubble some. If you drained it as part of replacing your temp bulb, you might want to just drive it up an incline once to get rid of any bubble that you might have at the rear of the head, but even with that done, it's not unusual for them to gurgle and bubble a little bit. Nature of the beast.

I doubt very much you will ever get it warmed up enough to get the needle to even move. Now if you want to take the upper bracket off the engine and have a machine shop ddrill and tap for the sensor you will get a reading as the top is always warmer than the bottom.