1gm10 overheat beeping after a longish run

[Gazza_G]

Me again! Impeller changed, but after about a couple of hours of running, the engine over heats when put in neutral…

A while back i had run it for about 15-20 minutes with the sea cock closed [i know!]. Could it be the thermostat needs changing?

it;s a reconditioned version. Any tipe useful!

 

[jamie N]

It's quite possible that the vanes from the old impeller are clogging the system.
If it's the thermostat, I believe that the engine can be run without the thermostat in place quite happily, however I don't know this engine, whilst others here have expert knowledge.

 

[alahol2]

I would suspect the residual heat in the engine block not being cleared by the reduced flow of coolant at tick over. I get a similar phenomenon if I stop the engine for 5 minutes then restart, the overheat alarm sounds for a minute.

 

[Tranona]

Remove the pipe from the pump to the inlet spigot into the block, from there to the thermostat housing and the housing itself. Suspect you will find a build up of deposits in the pipes and the inlet into the block. Do not run it without the thermostat as the engine will not reach working temperature.

 

[B27]

I would suspect the residual heat in the engine block not being cleared by the reduced flow of coolant at tick over. I get a similar phenomenon if I stop the engine for 5 minutes then restart, the overheat alarm sounds for a minute.

That's quite likely what's happening.
The metal of the head and block will be hot after a long run.
It might be worth checking the water flow is what it should be.
If the side clearance of the impeller is excessive, it might lose flow at low speed, or if the system is partially blocked.
You could probably stop the buzzer from sounding by running at lower speed for a few minutes before going down to tickover.