[JEP]

hi I had a little drive around the fields this evening and come on a problem. if I drive the David brown in high 3rd gear the water temperature will suddenly go so high and goes in to the red bar. however if I stop the tractor and drive in 1st gear straight after the water temperature will drop straight back down to the bottom of the green bar on the gauge. I was thinking could the thermostat be sticking or is the gauge not working properly or is there a problem with the tractor. I know the water is not escaping in to the oil as the oil shows know sigh of water contamination. however the block has a little crack which only leaks when not using  but when the engine is running it does not leak I regular check the water level which does not drop loads and is regular topped up. any suggestions on my problems and how to solve it

[pgkevet]

As someone who knows very little about this tractor model.. the first thought is whether it has a mechanical water pump and it's not pumping well at lower revs. Second thought that there's more engine load at higher gearing so it will run hotter.. specily if there's a problem in the gearbox.

Whether the crack in the block has anything to do with it (water pressure?) depends where it is. can it be fixed? Say a drill hole each end of crack to stop it running then clean crack out and fill... it'd tke an engineer to asnwer whether than can be tig welded or even just use JB weld