Remove build-up in thermo-siphon engine cooling loop?

[Lylat1an]

I suspect that my 1940 John Deere model H has some build-up in the coolant system because the temperature gauge needle barely moves while running, even when I max out the engine speed.

I don't have the proper tools nor a safe place to disassemble the machine, so I'm hoping there's a way to clean it out without disassembling the tractor?

 

[Richard G.]

Easy one to do.
Take out the drain plug under the head when the engine is cool.
Put a hose in the radiator inlet and let it the water flow through a long time.
This should flush out anything that is loose in the system.
Others will tell you to use vinegar and run the tractor.
I will let them explain that as I have never done it.

 

[Lylat1an]

Perhaps I misunderstood, but would that not only service the radiator since gravity would pull the water through the plug hole beneath it?

 

[Richard G.]

Temp gauge may be bad.
After you flush it through from the top, hold the hose on the drain hole and let it run till it comes out the radiator top and remove the hose and let it drain.
Do that a bunch of times and you will get it pretty darn clean.

 

[Mike(NEOhio)]

Are you saying the gauge doesn't move because of the buildup? Those things take a looooooong time to get hot and need to worked really hard to get
there. Use cleaning vinegar or a good radiator flush according to instructions. Keep the curtain or shutters closed.

 

[Mike(NEOhio)]

The plug under the head drains the whole system. Water flows from the radiator through the lower pipe into the head, then the block and returns
through the upper pipe to the radiator. Flushing from the bottom plug will push water up through the block and radiator.

 

[Loosehandle]

If it works don't fix it! If you have
working shutters close them and see if
the gauge moves after a while

 

[Lylat1an]

(quoted from post at 13:36:44 06/02/22) Are you saying the gauge doesn't move because of the buildup? Those things take a looooooong time to get hot and need to worked really hard to get
there. Use cleaning vinegar or a good radiator flush according to instructions. Keep the curtain or shutters closed.

I think I've only seen the needle budge once, and that was after a long time at fast idle.

The manual says to operate the engine at 180-190 Fahrenheit, but if it's not supposed to get that hot on light duty I'll leave well enough alone since I'm not planning to run it on kerosene.

 

[showcrop]

Do you have a shutter or curtain in place?

 

[in-too-deep]

The coolant will never get hot just sitting there running, even at full throttle. It needs to be working. Stop worrying.